The Fates of Nations - Paul Colinvaux

[]Colinvaux begins by setting up two basic central concepts for the study of any organism, including people: niche and breeding strategy.

As Colinvaux describes it, a niche is the way an animal makes its living. The niche of a panda is eating shoots and leaves. The niche of a koala is eating Eucalyptus leaves. The niche of the lion is to hunt and eat large herbivores. The niche of the ruminant is to graze on grass. The niche of birds is to eat insects. And so on.

The breeding strategy is dependent upon the niche. Each animal has far more offspring than are necessary for reproduction. As Colinvaux puts it, each animal has the number of children they think they can afford. Since there is no coordination across members of a species, each individual produces the optimal number of offspring  that would ensure their genetic material is passed forward into the next generation in a sort of arms race. Thus there are always more offspring than are needed to replace the parents.

 This means producing offspring well in excess of the resources available for that niche, leading to competition for the available niche space where those most able to get sustenance from their environment are the ones able to survive and reproduce. Sometimes mutations occur which give certain members of the species an advantage, a process known as natural selection. It should be noted that this process has no end goal or direction.

In any case, the competition is done by nature itself, which winnows down the excess offspring to suit the available niche. The niche itself, however, remains a fixed size.  

Producing more offspring has no effect on the size of the niche. When an animal lives in a fixed niche its population is fixed as well, no matter how vigorously the animal breeds." (p.53) "Each individual is progammed (sic) to thrust as many descendants as possible into the next generation, and it competition for niche space that winnows the surplus. (p. 52)
Some animals have a breeding strategy to produce large numbers of offspring, knowing that most will not survive (of course, they do not literally know this). Other animals produce fewer offspring but invest much more time and resources in raising them. Animals lower down the food chain need to produce a large amount of offspring; a "gambler" strategy where most offspring will end up feeding predators higher up the food chain, while animals higher up the food chain must necessarily produce fewer offspring. The breeding strategy is set by the niche. These are two interlocked concepts. Each animal breeds in line with its niche.

An animal's breeding strategy is designed to thrust enough offspring into the next generation to be able to compete for the available slots, but not so many that the survival of the entire brood  is threatened in the current generation. Thus, there is a sort of "Goldilocks" strategy that evolves over time based upon the niche that the animal occupies. Too few offspring and you will not secure a place in the next generation. Too many, and your children will not have enough current resources, also ensuring failure:
Having a few large young, and looking after them, is the best way to press your descendants into the populations of the future...But even for those animals with the prudent banking habits of the large-young gambit, there must still be a pressure to raise the greatest possible number of babies, producing a tendency to make the modest family hold just one youngster more. The  tendency is blocked or balanced by the danger that lies in trying for too large a family. If a couple tries for one youngster too many there may not be enough food to go round and the whole brood may be in jeopardy. One youngster too few, and your neighbors' descendants will swamp yours. One youngster too many, and you tend to lose whole line that wins will be the one which starts with exactly the right family size: the largest number of babies that can be reared on the food available, and not one baby more. There will, therefore, be an optimum family size for any species using the large-young gambit, and habits which result in this optimum family will be preserved by natural selection.
The human breeding strategy, then, is based on sexual habits that lead to a surplus of babies, balanced by patterns of behavior that reduce or halt this continued accretion by culling. The methods of culling are either deliberate (infanticide) or properties of social behavior (taboos) that probably serve a number of other functions as well. But, whether by infanticide or learned taboo, these methods of stemming the flood of babies to what is convenient all result from the use of intelligence. It is the purely human quality of a developed intelligence that allows our curious sexual appetite to be a useful part of our breeding strategy.
In any ecosystem, big, fierce animals that eat meat are always rare. This is because big, fierce predators by their nature get only a small portion of the earth's solar energy as it is passed down the food chain beginning with the primary producers which use the sun's energy directly by using photosynthesis, such as plants and algae. Only a fraction of the sun's energy is available to big, fierce predators. "Humans were rare as tigers are rare, because there is not much food to be won at the profession of big, fierce hunter." (p.53)

Humans evolved in a specific niche as well, just like every other animal. Humans evolved as big, fierce predators following herds of megafauna across the savanna while gathering a wide variety of plant materials, nuts, seeds, fruits, tubers, and so forth, along with the occasional seafood. With our omnivorous diet and use of tools and fire, we could pivot from different sources of sustenance as they became rare, thus acting as a sort of equalizer, keeping down the numbers of whatever species happened to be overabundant in an ecosystem and changing when they became rare. We have spent over ninety-five percent of our evolutionary history under these conditions.

We evolved primarily for Ice Age conditions, that is, humans are inherently creatures of the Ice Age. Far from being a harsh environment, it is the environment for which we are most ideally suited. While northern regions were colder, most humans were concentrated in the wide bands around the tropics, and the water locked up in glaciers meant that there was actually more land available in these areas, with plentiful prey. Savanna ecosystems covered more of the earths surface, and humans evolved as apex predators in these ecosystems. We are suited to small-scale social groups and low population density. When the last glacial period ended, the climate changed and much of the earth's megafuna started to die off. The savannas receded, and coastal areas disappeared (such as Beringia, the Sahul and Doggerland). Humans found their niche shrinking. They embarked upon a great experiment.

Humans, because they could manipulate their environment, broke free of their ecological niche. We could enlarge our niche at will using technology. We directed ever more of the earth's primary productivity to ourselves, starving it from other living things. We domesticated dogs for hunting. We domesticated herd animals and protected them from competing predators. We slashed and burned entire ecosystems using fire and replaced them with only the plants we wanted. We stored and redirected the flow of water on the earth's surface. We selectively bred only the plants and animals we desired, hijacking the process of natural selection. We artificially enlarged the food supply and made it more reliable. These were all ways of changing our niche.

Once we broke free of our niche, we broke free of the limitations on niche size imposed on us by that niche. While big, fierce animals are always rare, we began to become more common like social insects such as ants rather than apex predators. We ate lower on the food chain. Our flexible diets permitted this, along with our ability to pass things down through social learning and cooperate in large numbers. Our big brains, tools, and cooperation allowed us to access foodstuffs unavailable to other animals through processing, such as the small, dense packages of carbohydrates stored in plant seeds. We essentially became overnight herbivores instead of predators, something unheard of in evolution. With that came the negative health consequences we continue to see to this day.

When we invested in artificially changing the immediate ecosystem, it made sense to remain in one place rather than following the disappearing herds. This led to sendentism which, along with a more reliable food supply, led to population growth, and hence to crowding. Also, the arrival of soft foods such as grain and milk decreased weaning times and allowed for more children, changing the breeding strategy. Once you have made significant investments in your area, you get sedentism and private property. Once you have surpluses, you get inequality. And once you have population increase, you get crowding and social conflict.

Eating like an herbivore at the bottom of the food chain meant more people, but more people living unhealthy lives in drudgery, poverty, and misery. Instead of being just predators, man became both predator and prey. "The first farmers gave up the role of carnivores in the ecosystems of their times and took to herbivory as if they were cows or rodents. It was this habit of agriculture which let our numbers grow from the rarity of bears to something like the commonness of rabbits." (p.61)
Increasing the food supply by changing the niche gave our perfected breeding strategy a chance to show of what it was inherently capable. Unless we changed the breeding strategy, which we have never done, there would, inevitably, be a great increase in the number of people living. Each individual, remember, is programmed to try to thrust as many descendants as possible into the next generation, and it is competition for niche space that winnows the surplus. But, if more niche spaces can be made almost at will, there will be no more competition. All offspring raised to maturity will find a niche in which they can live and raise offspring of their own.  
The Darwinian breeding strategy of the animal that can create unlimited jobs for its offspring would lead to an unlimited number of survivors. Substitute the words "very large" for the word "unlimited" in the above sentence and we have one of the results of the great people-experiment of changing the niche without changing the breeding strategy: people have overrun the world.  
When we lived in a constant niche like all the other animals, there were essentially no population consequences of this perfected breeding strategy of ours. As the niche never changed, so the numbers of the people never changed. What has changed since those ancient times is not the breeding strategy, but the niche. We have learned to live not only as hunters or gatherers, but as farmers and industrialists as well. These are quite different ways of life from those of our ancestors, and they can provide for populations of quite different sizes. This is why our populations have grown since those early days: because the niche has changed. All of us still breed to press more of our descendants into the next generation than there is room for. In the old days this made no difference, because the job opportunities of niche never changed. When we started to change our niche, the opportunities for life went up, and our numbers rose accordingly.
Once we controlled our niche, this allowed for a wide a variety of experimentation with lifeways and living patterns leading to cultural evolution. Social learning became the primary means of passing down our ability to live in a certain niche. This also allowed us to colonize every area of the planet.
Original niche learning had little effect on our numbers, because every culture exploited similar varieties of foods. We were always hunters of gatherers. Ancient people learned their professions of life, just as the followers of modern professions learn theirs. It was this fact that made us ready for the dramatic changes of niche that were to come later. (p. 51)
The invention of institutions to cope with growing numbers is an ongoing process, continually unfolding, and the mismatch between our Ice Age habits and our modern circumstances is the underlying cause of many of social maladies we see today, from drug addiction, to teen pregnancy, to child abuse, to depression, to obesity.  
"We no longer live in the ancient human niche, but we still could, or rather, some small number of us could since there would not be room for many. It must, therefore, follow that we still possess the traits that equipped us for that ancient niche, even though we have turned our skills into living in quite different ways. We have invented and learned most of our new ways, so they must be wholly new. But some of the ancient adaptations that we did not have to learn are still with us." (p. 47)
As we came together in farming village-based societies, one's niche was no longer getting sustenance from our immediate environment, but rather one's role in then the superorganism known as society. New niches emerged such as farmer, herder, artisan, merchant, priest, king, soldier, slave. This gives rise to a new definition of niche. Normally it is how an animal gets its food and makes its living. But Colinvaux also uses it to describe how people make their living; a definition common today as well. We speak of niches such as professional, politician, bureaucrat, worker, laborer, criminal, and so forth.

Following ecology, Colinvaux dives social niches into broad niches and narrow niches. Broad niches are what we describe as wealth, and narrow niches are what we describe as poverty. Upon the rise of society, most people were crowded together in the lower, more undesirable narrow niches as slaves and primary food producers, toiling away for the benefit of the upper niches. However, the size of these niches changes over time based on conditions such as the number of people in the society, the available resources, and technological development. Many of these changes drive history, as he describes later on.

As Colinvaux describes, a niche is a way of making a living. In an example he provides, there are only so many spots for aeronautical engineers. That niche is finite; it cannot expand simply by producing more aeronautical engineers. It can only expand if there is more of a need for aeronautical engineers, such as a boom in the aerospace industry, or the discovery of new key technologies. The same thing goes for lawyers, doctors, senators, or any other profession. Just like animals who occupy an ecological niche, each societal niche is of a fixed size, and therefore if there are more competitors  than there are spaces available to them, social conflict must be the result:
We know that the number of people who can earn their living as aeronautical engineers is set by the job market for these highly specialized skills. The number of people actually filling the niche of aeronautical engineering cannot be altered by training more engineers in college but only by making the aircraft industry boom. An ecologist would say that niche-space determines the population of the species "aeronautical engineer," just as niche-space determines the number of squirrels. Similar arguments apply to all human professions, just as they apply to all kinds of animal niche. 
Western societies have recently tried a large-scale experiment in flooding niche-space when they expanded the university population, particularly the graduate schools...Universities have produced very large numbers of these presumptive professors, rather as if the squirrels had a very good year for raising young. But the number of professorships sets the opportunities for professing...Now surplus bearers of doctorates cannot accept the scholar's tenure, however cum laude their degrees...People have the quality, not shared by other animals, of changing their niches. Surplus squirrels always die, but surplus scholars, lawyers and aeronautical engineers take up other trades. Yet it must be remembered that all human professions have this in common with animal niches, that the number of individuals following each profession, or niche, is absolutely set by the conditions of their ways of life. Niche sets number. (pp28-29)
If you expand the candidates for a specific niche space without actually increasing the niche space available, all you do is increase the competition, which inevitably leads to more social conflict, not less, including oppressive governments and caste systems (see next post). More education does not magically call forth the need for more jobs. Thus, education, rather than being a silver-bullet solution for poverty, often leads to more problems than it solves. In places like Africa, there are already many more educated people than there are niches for them. Many of those educated poor leave, where they increase competition for niche space in wealthier societies, causing cultural clashes, and increasing competition for a limited number jobs:
When a country starts on mass education even before there is a rapid expansion of the niche-space through technology, as many in the Third World are doing now, the result must be a social crisis. The crisis is like the excess production of aeronautical engineers, which I described earlier, but on a national scale and for all the appetites of middle- or upper-class life. In a version of the old saying about more chiefs than Indians, it is a deliberate production of more chiefs than there are chief jobs available. The only escape for the surplus of the newly educated in one of these countries is emigration, if some more developed country will take you; the only escape for the government is repression of the new intelligentsia. The developing world is rich in examples of both these measures. (p. 79)
This is especially relevant given the economists' arguments for "more education" as the solution for the problems of the developing world, including both chronic poverty and overpopulation (see below).

Crowding also brought forth the need for governments, and those in these administrative and leadership roles occupied the most desirable niches in society. It also brought forth niches allowing  specialization in the art of violence, such as generals and soldiers. Because big-game hunting requires a high degree of specialization and leadership, we were already primed for those things during the Ice Age. But now, management, authority, and lifetime occupational specialization became permanent features of the human condition. We became specialized, as insects are specialized.
"Our primeval niche let us take kindly to government because the old social life involved divisions of labor. Hunting in groups needs collaboration and mutual support. Even herding, which ties people to beasts, requires some directed collaboration, and agriculture ties people to ground and food plant, so that government for any society more dense than a one-family plot is essential. The institution of government did away with the nightmare of people being reduced to perfectly equal peasanthood. But escape may be only for the fortunate few--the governors." (pp. 68-69)
As agricultural village societies became increasingly large, they eventually evolved into the first cities. Inside these dense, urbanized cultures, for the first time people came into daily contact with large numbers of unrelated strangers. New social institutions emerged, such as money and organized religion, as did new social roles. Eventually, city-states emerged as the new dominant social structure in the fertile river valleys, and these city-states were the incubators for crafts, writing, architecture and metalworking:
The organization that we call a "city-state" is the logical, indeed the inevitable, outcome of the invention of agriculture by an animal of social habits. Agriculture requires settlement. An unchanged breeding strategy makes that settlement dense. Government in a dense community requires specialization. And a dense settlement containing both rulers and ruled must inevitably divide up the country into land to live on and land to farm. The city-state has emerged, along with a rationale that requires people within it to have different specialties—that is, different niches...The need for government in dense communities did more than just save a few individuals from the worst consequences of our change of niche. It also allowed further increases in the carrying capacity. Government could ration, distribute and hoard. Surplus and deficit could be balanced from place to place, and from season to season, ensuring an even flow of the necessities for life, making the luxury of large families the more safely enjoyed.
The people who occupied the upper niches in society, such as government, religious and military authorities, were able to live much in the same way as their Ice Age ancestors had. They had access to a wide variety of resources such as foodstuffs (especially protein), sex, durable goods, artistic pursuits, leisure time, and lives of relative luxury, ease and comfort. Their lifestyles allowed for variety in their daily routine and consumption habits of things like food, drink, and sexual partners:
"The immense flux of resources required for each niche-space of wealth can best be realized by reflecting on just one propensity of the wealthy, the propensity to choose. The wealthy seek variety, both in daily activity and in real opportunity. But any freedom of choice must mean that, for everything done, there be something left undone. Freedom and wealth, which are to some extent linked, require very many resources per niche-space. The wealthy, and the truly free, therefore, must be rare." (p.71)
By contrast, life was much worse for the vast majority of peasants who lived under the whip of an overseer, having to cope with overcrowding, substandard diets, malnutrition, backbreaking, routine work, celibacy or monogamy, and disease. This led to the permanent institution of wealth and poverty, where the wealthy can command ten, fifty, a hundred, or even a thousand times more than the average person; something impossible in a hunter-gatherer society:
The organizers in a city-state, be they governors, bureaucrats, businessmen or priests, led active, wide ranging lives that needed many resources; an ecologist would say that they had a broad niche. The mass of the people needed much less, little more, in fact, than would be wanted by that ideal agricultural peasantry; they had a narrow niche. The broad niches of the governors meant wealth, but then the narrow niches of the mass could be given a new name, "poverty." "Wealth" and "poverty" are but names we give to two extreme kinds of ecological niche. The niche of wealth demands more resources per individual than does the niche of poverty. Wealth even takes more food, for a wealthy person actually eats more calories than does a poor person. Even more importantly, the wealthy person tends to eat higher on a food chain, requiring more meat. This means that any patch of real estate probably can feed between ten and a hundred times as many of the very poor as of the very rich. How many rich people there can be, therefore, depends on how many people are trying to get their living from the land; it depends on population density...Wealth and poverty are both inventions of agriculture-based humanity, but poverty is more of an invention than wealth.  We make people poor by denying them the types of food, activities and space that were consumed in the primeval human niche, whereas the wealthy retain many of these old assets.
Because people were not naturally happy occupying the narrow niches, competition for the upper niches became intense. But because it takes more resources to make a broad niche, however, there are necessarily less broad niches than there are narrow niches, and hence less freedom:
We must think that our most perfect evolutionary triumph would be a society of agricultural peasants, sedentary, marvelously numerous, living in a landscape set the very minimum of animal food, freed from the very minimum of animal food, freed from the threats of predatory or competing animals, and having a family size again brought down to meet the needs of replacement and set by the fact that there should be no food to rear more than two or three children per couple. Peasants such as these would be the ecological apotheosis of humanity...  
But people have not been able to change the human niche so completely as required by this triumphant evolutionary nightmare. They have not wanted to be the perfect food-raising food-consuming peasant. Many individuals resist peasanthood very strongly indeed, trying to preserve more ancient ways of life and even wanting to do things that the ice-age peoples could not do; they want to go adventuring like a hunter, to paint, to craft, to make machines...
Our breeding strategy, however, remained unchanged from that of our ice-age ancestors: each couple continued to raise the number of children they thought they could afford. Colinvaux's key insight is that the poor will always have more children than the rich. This is because the children of the rich require more resources to raise than those of the poor. The rich require a lot of resources in terms of food, shelter, money, education, assets, et cetera, to raise children in the manner to which they are accustomed. By contrast, for poor people, raising children requires only minimal resources. There are almost always enough resources for another starving peasant, but not for another prince. "Each human way of life will have its own characteristic size of family." (p.41)
Because it takes scant resources to raise a child in poverty, the hopelessly poor will opt for large families. They are doing their Darwinian thing, estimating the number of children that can be raised to compete for niche-spaces in their world of chronic poverty and then arranging to have families of this calculated size. The wealthy, on the other hand, must plan for each child to be able to compete for niche-space in a world of wealth...When the Darwinian cost-accounting is done in a wealthy family, the stark fact is that the certain and successful rearing of a child, fully equipped to become itself a parent in its parents' world, requires a very heavy investment. Wealthy parents, like poor parents, seek to raise the largest number of children that they can afford, for this is their animal breeding strategy which has never changed. But wealthy people cannot afford very many children, despite their wealth. (p.42)
Across a whole society, breeding strategy is based upon hope, specifically the hope that a person's children will have a higher living standard than their own. This means that growing, prosperous societies will inevitably have growing populations, Times of plenty lead to a rising populations, and hence more competition for niche spaces, especially for the broad niches. Thus, rising numbers lead to rising aspirations.

Colinvaux pours cold water all over the idea of the "demographic transition." This is  the observation, scientifically unsupported, that families in wealthier societies tend to have fewer children on average than poorer ones. This is explained by the above. In richer societies, the option of occupying a relatively broad niche will still cause people to have fewer children than people who do not have that option. But there will continue to be a surplus of children. The only reason that the surplus is slightly smaller is because wealthier families demand more resources for each individual child than do poorer ones. Since rich children command more resources per capita than poor children anyway, relying on increasing wealth to save the environment is a strategy condemned to failure:
And yet a noisy propaganda is about which denies that rising populations cause poverty. We are told by most eminent politicians and international experts that the rising numbers, far from being a cause of poverty, are in fact a result of poverty..."Poverty is the cause of large families" they say. "Do away with poverty—by foreign aid or by giving to charity—and the population problem will take care of itself." It is an appealing, comforting hope; but it is false. 
People who lean on this propaganda are deluded by the very true observation that the moderately affluent have smaller families than the comparatively poor. They say that giving poor villagers of the Third World the money and education of someone living in a French or American suburb would result in their having smaller families, as indeed it would; provided that the new affluence was safe for a generation or more. The poor villagers would pass through a "demographic transition," as I explained before. Affluent couples cannot afford as many children as can poor couples because many resources are required to raise a child to affluence...But this does not mean that poverty causes population growth; it is the growth that causes poverty, and the affluent West can lose its affluence by packing more people in. Poverty is growing in inner cities already. 
It can happen, and often does, that populations grow more quickly in poor countries. But this does mean that populations do not grow in wealthier states as well. In fact, we know that they do...What matters is the eventual population density. It is the number of people per unit of resource that determines the size of a niche and, hence, what we call a standard of life. Coping with more people in each succeeding generation is the ultimate drive for technical innovation...But poverty will always be present, because any large increase in resources produced by new technology will be taken up within a few generations by the provision of more poor people. (pp. 73-74)
Only chronic poverty and lower living standards can permanently slow long-term population growth:
Smaller families for the rich than for the poor are explained and predicted by the ecological analysis of the human breeding strategy, as we have seen. But this does not mean that numbers in a rich society will not rise, only that they will rise more slowly. Breeding strategy still ensures that each couple will raise the largest number of children it can afford and, under most conditions of wealth, this is likely to be more than enough to replace the parents. Making the poor wealthy will slow the rate at which children are raised, giving us more time to anticipate or plan the historical happenings that their crowding will bring, but it can never stop the children coming in excess supply. (pp.42- 43)
Neither will birth control work. Since people modify their breeding strategy based on their niche, people in narrow niches will continue to have the optimal number of children for that niche. Access to birth control is still dependent on them actually using it, which is solely a matter of individual choice, absent some sort of compulsion. And those at the lowest niches of society with the fewest resources need to have the largest number of children:
It is essential to realize that people of poor countries have their large families from choice. The poor themselves will tell you that they need to have children to look after them in their old age, or to have sons to go out to work when they are ten years old, or to have daughters whose marriage will bind families together. They might even say that children are a "comfort"; that they like children. These are but ways of saying that they are looking to the number of children decreed by their way of life, or the number demanded for them by the workings of the human breeding strategy. In either language, the poor have large families because they want large families. Providing the poor with birth-control devices will not result in fewer children.
Only desperate poverty has been shown historically to slow the rate of population growth:
But it is still possible for the human breeding strategy to cause population losses, as well as population gains. This will happen when a community is reduced to such despair that the average opinion of the ideal size of family puts it close to zero. Or, if hope yet allows some couples to start families, then the conditions of the people are so desperate that they cannot succeed. A single generation of desperation can remove a whole community for good. It is to this possibility of near total failure of the breeding effort, not to massacres of adults, that we must look for the decline of populations in history...(p. 44)
This leads to another of Colinvaux's critical insights, which is that people in the more desirable niches are the first to feel the effects of crowding. They also feel the effects of crowding more acutely, since they are accustomed to a higher standard living than the masses. This is counterintuitive. We naturally think crowding is felt more acutely by the people at the bottom, and that they are eventually are so staved of resources that they are driven to desperation and revolt. 

Not so, says Colinvaux. Rather, the swelling ranks of poor put pressure on the wealthy, who will turn to various measures to cope with it. It is the attempt to crowd ever more people into the broader niches which is the primary driver of attempts to expand the ranks of those niches by various means such as war, colonization, trade and technological advance; or ways to restrict access to them such as caste systems and repression."Politicians nowadays talk of "the population problem" as if it were mainly a worry for poor nations and the underprivileged, but this is wrong. The wealthy are the ones to be squeezed because the wealthy use the resources that the new crowds will want." (p76):
 A broad niche requires numerous resources; an expansive way of life can be provided for only relatively few. But more young people equipped to live in an upper-class way will keep coming in succeeding generations as our breeding strategy manufactures more people. Niche-theory predicts, therefore, that rising numbers will always cause trouble for the wealthy before they cause trouble for the poor.
Technology is another way to grow the available niche space, but this strategy was necessarily limited in the ancient world. Since technology changed fairly slowly from generation to generation, population growth was necessarily faster than technological growth. Except during brief periods of either low population growth or rapid technological advance (such as the last one-hundred and fifty years), rising numbers have always led to more poverty:
Every couple, rich and poor alike, continued to rear as many children as it could afford. Numbers always rose. The extra resources wrung from the land by cleverness and industry always went to supporting more people at the old levels. As fast as a few individuals could be raised out of poverty, as fast as the actual numbers of people living richer lives increased, so also more babies were born into the world to swell the actual numbers of the poor. 
Population growth is a geometric, or exponential, process. The cleverest of people, and the most enlightened of governments, have never increased the flow of resources exponentially at an even faster rate than the growth in demand represented by the extra mouths, except for short periods of rapid technical advance. Industrial societies of the West are experiencing one of those short periods of rapid advance at the moment, and there have been others in the past. But always a plateau has been reached. It must be so. The rate of increasing production falls but the rate of population growth does not fall. Then poverty must get worse and more visible, for not only do the numbers of people who must be poor increase, but each poor family finds itself poorer and poorer....Ecology's first social law may be written, ''All poverty is caused by the continued growth of population." (italics in original)
Rising numbers inevitably cause more poverty, and more pressure on the higher niches. This leads to people in the higher niches taking various measures. To cope with an excess of aspirants to the broader niches, elites of various societies have turned to a variety of strategies, and it is these strategies which drive the historical process:
For the early stages of the growth of a civilization, therefore, niche theory predicts life in settlements, continually rising numbers, a ruling class living in broad niches that include many dimensions of the primeval human niche, technical innovation from those who have broad niches already, the persistence of poverty, and an actual increase in the numbers of the poor. 
Ruling classes that feel themselves threatened by the social pressures of a rising population have only two courses of action open to them. They can find more resources to provide good niches for more people or they can restrain the pressure on niche-space by a system of oppression. The most interesting ways of increasing the flow of resources include trade, colonies and war. These are always tried. The alternative, constraining the appetites of rising numbers by some system of force, is also always tried. It involves regimentation, bureaucracy, class, rationing and caste.
Thus, it is population growth caused by the various breeding strategies, and the effects of crowding on the broader niches which provides the driving force and distinctive episodes in the historical process, from the wars of conquest, to the colonization of far-off lands, to the wholesale abandonment of the countryside, to the establishment of long-distance trade, to the rise of surveillance states. In the following chapters, Colinvaux lays out his theory of why history happens according to the ecological principles described above:
Behind all the great climactic struggles of history we will find symptoms of an expanding population. Whenever people have been ingenious so that the quality of their lives has improved they have let their numbers rise. The demand for more resources for the better life has always been more than the prevailing political systems could provide. And the grand themes of history have been the result: repressions, revolutions, liberations and always, in the end, aggressive war. 
Perhaps little wars and petty repressions can often be explained as being caused by no more than human wickedness and animal passions, as various social and biological writers have argued. But all the truly great wars of history, those that ended with shifts of peoples  and the remaking of maps, were caused by increases in the numbers of people and associated increases in demand. We can examine the wars, the growths, and the falls of civilizations from ecological principles which describe how resources must be divided between people and which show consequences of changing the numbers of those people. From this study a predictive theory for the fates of civilizations, including our own, will emerge. (pp. 23-24)

People's breeding strategy is based on their social niche. Those in narrow niches require much less resources, and hence breed more children. The children of those occupying broad niches demand more resources per capita, and hence there are less of them. Nevertheless, each couple raises the number of children it thinks it can afford. This leads to rising numbers overall, and more competition for spaces in the broad niches. This leads to social unrest. Thus the pressure of rising numbers is felt by the upper classes first, rather than the mass of poor people below, because they have the resources and lifestyle that people in the lower classes desire:

Ruling classes that feel themselves threatened by the social pressures of a rising population have only two  courses of action open to them. They can find more resources to provide good niches for more people or they can restrain the pressure on niche-space by a system of oppression. The most interesting ways of increasing the flow of resources include trade, colonies and war. These are always tried. The alternative, constraining the appetites of rising numbers by some system of force, is also always tried. It involves regimentation, bureaucracy, class, rationing and caste. 
(pp. 79-80)
Because the effects of crowding are felt in the ranks of the broader niches first, political revolutions tend to come from the ranks of the upwardly-mobile middle classes as their aspirations are frustrated. It is rarely instigated by the peasant classes, and even when it is, it is rarely successful. We see this throughout history. Even peasant revolutions which are successful are usually led by people from the ranks of the upper  or upper-middle classes, such as Maximilien Robespierre, George Washington, Simon Bolivar, Vladimir Lenin, Mao Zedong, Fidel Castro and Che Guevara.
Middle and upper-class niches are inventions. They are developments of our original trick of changing the primeval niche through agriculture and settlement. When new niches are first invented, few people live in them; an ecologist would say the niches are "empty." We should expect, therefore, that many generations must pass before life in these new niches could be crowded. It must follow, then, that the social unrest, which is the prime indicator of crowding in these better niches, will always be long in coming. Lulls of social peace occur, particularly as a small inventive state begins the process of growth. Social unrest follows, always as a distinct episode This is why revolutions are revolutionary, a sudden upset of the old ways, as in France and Russia, or the upheaval of 1848 when kingdoms collapsed all over Europe. These events all followed technical change and rapid population growth, but were decades in the making (p.78)

When those in power must lose privilege because the numbers of their own kind rise, social unrest must follow. Social unrest, therefore, is a necessary consequence of changing the niche without changing the breeding strategy. Furthermore, the unrest will be a middle-class phenomenon and probably episodic. The troubles come from trying to pack in a few more of the relatively wealthy, not from packing in many more of the relatively poor.

I suggest it is axiomatic of human history that social upheavals, even revolutions, do not emerge from the ranks of the poor...They come from disaffected individuals of the middle classes, the people who experience real ecological crowding and who must compete for the right to live better than the mass...The episodic quality of these revolutions comes about because scattered disaffection alone may have little result. Individuals can wage a brief struggle for the niche of their parents, then accept defeat and sink to a narrower vocation in life. (pp. 76-77)
One way to cope with the surfeit of claimants to the upper-class niches over time is the establishment of a caste system, in which access to niches is limited by some sort of social convention, thus tamping down competition and social conflict. This could be blood relations, or it could by something else, such as wealth or ability. Colinvaux speculates that the extraordinary stability of certain Asian societies was due to long-standing caste systems. "It was the stability of neither change nor opportunity." (p. 83)

We think of caste systems as something from ancient India, but there are many varieties, even though they are often not perceived as such. In the ancient near East, slavery was hereditary, as was kingship. High priests were often a separate caste based on blood relations (such as the Levite tribe of Israel), and you couldn't become Pharaoh by working on the pyramids. The formidable Spartan warriors were made possible by the Helot slaves who made up the bulk of Spartan society, toiling away to produce the agricultural surplus and allowing specialization in warfare. Roman society divided into patricians and plebeians. In the societies of classical Greece and Rome, slaves made up to eighty percent of the population.

Medieval knights and lords were supported by serfs who were tied to the land they farmed. China had an imperial examination system whereby one could increase one's status through intensive study (but not become emperor). Many positions in British society could only be held by the aristocracy up through Victorian times and beyond (a military commission was bought, for example). Today, we might say that access to the broad niches is restricted by your family's wealth. Nearly every large, complex society in history has developed some sort of caste system. "Castes promote a stable society because they ration people to jobs, not all of which are the most desirable. They ease the pressures of crowding on the broad niches of the most cultured. Furthermore, castes are logical for an animal who maintained its primeval niche by learned taboo." (p. 81)
Castes have been described from many ancient societies--Egypt, Greece, Rome, Persia, Fiji as well as India and Europe of past centuries. Castes are apparently ubiquitous. They ration resources among the populace when broad niches are not attainable by all. They raise and educate an individual to one of the many niches of society. (p. 84)
Caste systems must largely fail before universal education, which, at least in part, trains people to choose from a variety or vocations for which they might be prepared. But education does not remove the need for constraint; if caste no longer works to choose a niche, some other constraint has to be invented. In a market economy, the individual is allocated a niche by economic circumstance. In a socialist state the individual is allocated a niche by a government official. But people are still sent to a way of life that has to be, for most of them, less than the best. It is always crowded round the broader niches, and the more dense the population, the more crowded it will be. The defenders of a high way of life must push against the competition. Social oppression is an inevitable consequence of the continued rise of population. (emphasis in original) (pp. 84-85)
As described above, competition for prestige niche space leads to social oppression by the elites. As societies become more crowded, political repression must always follow. Societies with low population density have more freedom. As the effects of crowing become more acute, the governmental authorities impose ever more restrictions on behavior. It is societies with low population density and plentiful niche space which typically enshrine individual freedom and liberty as part of their highest ideals.

Societies that talk a good game about freedom and liberty have always been those where there were plenty of spots available in the more desirable niches to accommodate the aspirants to them. They tended to be growing, expanding societies, with plentiful resources and low population density. But crowding inevitably invites repression, as people occupying upper niches try to limit claimants to their positions. This leads to a repressive police state. Freedom and liberty go by the wayside, and democracy withers away, even though it is still honored more in the breach than in the observance.
Crowding in the upper ranks must produce a response in the government of society. We can expect that the descendants of those who once labored for the poor might well become inward looking, concerned only with the defense of their own privilege. Like poverty itself, a gradually repressive ruling class must be the inevitable consequence of indefinite population growth. (p.79)
This leads to the first broad strokes of Colinvaux's ecological theory of history:
After the original inventions of wealth and poverty, therefore, niche theory predicts:
  • That middle and upper classes will be the first to feel the pressures of crowding.
  • That ruling classes which previously were sympathetic to the mass will become selfish and oppressive.
  • That social troubles will be episodic rather than continuous.
  • That methods of allocating people to the more narrow niches will evolve. Caste systems are the most human [sic] of these methods, but capitalist economies and socialism have their equivalents.
  • That even under oppression, population will be stable only if the optimum family for the most miserable class is less than the needs of replacement.(p. 85)
Eventually social conflict becomes intolerable, and rising numbers cause societies to expand and lash out. Colinvaux describes three common methods of doing so - trade, colonization, and war.
When you run out of niche-space for the good life, you can always look for more somewhere else—through trade, through colonies and through aggressive war. We think of trade as "good," colonies and conquest as "not so good." Yet all three serve to tap the resources of other people's land. And they all need military hardware for success. (p. 85)
As societies seek to expand, they inevitably come into conflict. Colinvaux explicitly rejects the "great man" theory of history. Instead, he argues that the victorious society is always the one with the superior military technique. He uses numerous examples throughout history, from Egyptian war chariots, to the Macedonian phalanx, the Roman legion, the Iranian heavy cavalry, the steppe horse archer, the English longbow, the French massed infantry, to the Panzer divisions of World War Two and finally nuclear weapons. According to Colinvaux, the victorious society is always the one with the superior military technique.

Where do these techniques come from? Conflict zones are the crucibles for the development of these techniques. A great portion of the book is given over to military history to elaborate this point, and these vivid portions of the book are worth reading in their own right. Colinvaux argues that the conquests of Alexander the Great were due to the superior military technique of the Macedonian phalanx, which had been forged during centuries of incessant conflict between the numerous city-states of the Greek peninsula competing over a limited amount of land. Furthermore, Greek colonization and trade had led to the development of a superior navy, which increased the advantage (see below).

This is what allowed Alexander to defeat the Persians in battle. That Alexander was a brilliant military strategist was secondary to the fact that he had the superior military technique. Alexander's conquests are an example of a growing society expanding to take land from its neighbors, and hence acquiring niche space.

Colonization is another way of expanding niche space. The parent society sends out colonists to form children societies. The branch society often takes land from the natives by force. They can do this because they have developed superior military techniques in the crowded conditions of their parent societies. They also have superior ways of making a living that allow them to support more people at higher population densities.

Again, the ancient Greeks provide a perfect example as they spread out across the Mediterranean, forming colonies such as the city of Syracuse in Sicily.  The Phoenicians are another example, as they used trade to create new niches for their people around the Mediterranean, and founded colonies such as the city of Carthage on the coast of North Africa, which grew into a military power in its own right. Colonization and military conquest are on a continuum of seizing niche space from others:
True colonies represent the simplest form of land theft. You send out soldiers, occupy a piece of land and fill it with settlers. You carry on your own expanded way of life away from the parent city, not so much relieving congestion at home as providing the necessary opportunity for the increased numbers in each generation. When you have many colonies, you might fill in the gaps between and make a small nation-state. All colonization is aggression, but there is a gradient from making a small settlement to wholesale annexation of aggressive war. You use your superior weapons to take niche-space from others, by force. (p. 90)
 The conflict between Rome and Carthage is illustrative. Rome came into conflict with the neighboring tribes of the Italian peninsula. Through centuries of warfare, they developed the Roman legion, anchored by severe discipline. Carthage, unable to expand into the interior of Africa due to geography, terraced the hills around the city and practiced an  intensive, highly productive agriculture, and turned outward to the sea in trade and colonization. They founded colonies all around the Mediterranean, including colonizing the Iberian Peninsula. This caused them to develop into a formidable naval power. "Trade is the simplest of the three ways to expand. You say where you are and fetch objects you want in ships." (p.85)

Colinvaux's insights on trade are especially interesting, especially given their prominent role in modern economics. According to him, trading regimes develop not to supply necessities to the parent country, but from a desire of the middle and upper-middle classes to expand niche space. Those who are frustrated with not enough niche space in their respective societies look outward to buccaneering trade to provide sufficient lifestyles for themselves by tapping the resources of other people's land. Aggressive, ambitious individuals who find their ambitions thwarted at home turn to adventurous trade to create new high-status niches, and have done so throughout history.

Trading regimes expand niche space not just for the traders themselves, but also for other people in the home society as well. People at home must make the articles for trade. New positions are created marketing and distributing the articles of trade. Trading societies are expansionary, which leads to higher living standards and population growth for such societies:

Our historians talk with approval of the "merchant adventurers," the people who sought a broader way of life through trade. For trade to work, there must be a market for imported commodities, but this market will result from the very increase in population which drives the better-off to trade. The way must always be open, therefore, for sons of the wealthy to find lives of freedom in importing objects that the masses want. We expect trade to develop not in the service of the hungry poor, but in the service of the aspiring middle class. The ecological hypothesis predicts trade to be important in a state only when there are too many people trained to better-class ways. But trade must also have an immediate effect on the opportunities open to all classes, because the parent society has to make the objects to be spent in trade.(emphasis in original)
In creating niche-space (jobs) for children of the wealthy, trade must also create jobs (niche-space) in the parent state. Because people must make things to sell outside, trade multiplies the niche-spaces available in the crowding state. First people can find a broad-niche life by engaging in trade, then other niche-spaces are made at home for those who supply the articles of trade. But even the stay-at-homes are getting part of their living from other people's land. It is quite wrong to think of those who stay at home as being supported by the homeland, because many dimensions of their niches are supplied by the foreign states who take their manufactures.(p. 86)
We've seen this before. There has always been a conflict between merchants and the aristocracy. In ancient Egypt and Rome, trading was strictly controlled by the state. Chinese merchants and traders were often checked by the aristocracy, who feared their power, and the Samurai in Japan controlled trade to an extreme extent.

Where trade did develop, it was wealthy, middle-class individuals denied from places in the aristocracy who were at the vanguard of trade. In Spain, Portugal, England and the Dutch Republic, it was wealthy middle-class individuals (the bourgeoisie), not the peasants, who established trading regimes. These led to prosperous societies at the expense of other cultures. Classical Liberalism can be seen as a debate between these two forces. It can be said that after the Glorious Revolution and the establishment of William of Orange on the throne (funded largely by British banks), the aristocracy decisively lost out to the merchant caste, sealing the fate of England. The conflicts between merchants and landowners would continue throughout the nineteenth century, as seen in the debate over the Corn Laws.

As trade grows, living standards increase for all. This causes population growth, causing trading regimes to become dependent upon trade over time to feed their growing populations. But--and this is important--expanding populations are a consequence of successful trade, not a cause of it.  Again, this seems counterintuitive:
After trade becomes commonplace, the hypothesis predicts a second and inevitable consequence: the mass of the people will become dependent on imports for their very subsistence, very likely even for their food. They do this because their numbers go on rising after trade has become important to the state, as well as before. This late-arriving portion of the population is dependent on imports for necessities. Once, therefore, a state begins seriously to trade, the rising numbers that trade makes possible become dependent on continuing the trade.
This analysis departs drastically from conventional wisdom about trade. We usually think of trading states, say modern England or Japan, as being driven to trade in order to feed their people. Modern politicians in those countries make speeches about "having to export in order to live," which leads people to think that the dense populations came first, and that some desperate necessity drove the crowded masses to resort to foreign commerce. But the ecological analysis denies this. The crowded masses are not a cause of trade, but a consequence of it. The only way in which crowding causes trade is through the pressure on the lives of the better off. Children of wealthy people engage in adventurous commerce to maintain their own standards of life. By doing so, they make it possible for more people to be raised in subsequent generations. These new people are the ones who are physically crowded. They are dependent on commerce, certainly,  but they only appears as a result of the commerce started by others.(p. 87)
Colinvaux's other insight about trade is that trading regimes must necessarily develop into military powers. This is because trade is dangerous: you are moving large amounts of goods through hostile territories where they can easily be seized by hostile governments or pirates. To counteract this, military techniques must be developed that are not only capable of projecting force, but also sacrificing as few soldiers as possible, since you are typically not fighting on your home turf. This leads to the development of powerful weapons and military techniques by trading regimes. We also see this throughout history, from the Phoenician trade and colonies, to the Greek and Carthaginian navies, to the Venetian Arsenal, to Islamic merchants, to the Spanish and Portuguese galleons, to the British Empire which ruled a quarter of the earth's surface at one point. These thasallocracies develop superior weapons and military techniques that allow them to dominate much larger populations with small amounts of people.
A civilized soldier employed by the merchants will be armored, for he fights not out of pleasure but from calculated necessity.Getting hurt is to be avoided. Weapons, tactics and discipline will reflect the organized life of his thriving city. The hypothesis predicts, therefore, that an emerging trading state will develop the best weapons and armor that their technology can produce; the city will take, as it were, a cost-effective attitude to the arts of war. (pp. 88-89)
Colinvaux's insights on trade, then, can be summarized by the next predictions of his ecological hypothesis:
We can add to the list of predictions of the ecological hypothesis:
  • That trade will develop as the niche-space of middle and upper classes becomes crowded.
  • That opportunities in manufacture increase as trade grows.
  • That the population rises and grows denser as a consequence of trade.
  • That the trading state acquires advanced weapons and an army. (p. 89)
As Roman society grew and prospered after the Carthaginian defeat, this led to rising numbers, and rising numbers led to an emptying out of the countryside. This leads to another of Colinvaux's conclusions--that rising numbers in a society will lead to an emptying out of the countryside and a crowding of people into cities. Again, this may seen counterintuitive. "Surely we need more food producers out on the land to produce enough to feed all the hungry mouths in the cities," is what you might be thinking.

Not so, says Colinvaux. The reason is because it allows the landscape to be farmed more intensively through large farms than by smaller ones. Throughout history the countryside has emptied out to feed growing cities ever since ancient Mesopotamia. This is because large farms worked by slaves producing monocrops for export leads to greater surpluses than small-scale subsistence farming. A concentration of wealth allows small farms to be brought up by bigger ones, eliminating niche spaces for farmers. They then head to the cities to be merchants, artisans, shopkeepers, soldiers, or simply layabouts. It is far easier for governments to feed urban masses centralized in a dense city than it is to feed a population dispersed throughout the countryside.

This emptying out of the countryside was remarked upon by numerous ancient Roman writers. Colinvaux argues that these writers looked at the empty countryside and abandoned small farms and concluded incorrectly that this was a consequence of the population shrinking, when it was, in fact, a sign of the population growing.

We know that the cities of ancient Rome were sustained by the massive shipments of grain from places like Egypt and North Africa, along with other commodities such as olive oil from Spain. The empire could only be sustained by a vast shipping network moving surpluses from sparsely-populated rural areas to feed the masses of idle, hungry citizens in the urban areas who could revolt at a moments notice. It's notable that years of incessant conflict between the patricians and plebeians in ancient Rome ceased after Augustus seized Egypt and shipped the surplus grain to Rome to placate the restless masses (bread and circuses).
...There is a drift from the land as peasants are displaced in the interests of increased production. This happened in ancient Greece and Rome no less than in the time of the enclosures in Tudor England, or in modern industrial states. The process can be seen in the development of every civilization. Feeding great numbers of people is more easily done if they are brought together in dense settlements; running the agriculture needed to supply those dense settlements is more efficient in the larger agricultural units of agribusiness. And the "drift from the land" is a predictable consequence of a dense population growing denser. It follows, therefore, that partial depopulation of the countryside results from population growth: the land looses [sic] people even as the total population climbs. It is easy to mistake this loss of people from the country districts as evidence of a population fall. Roman Pliny made this mistake and there are historians who have followed his errors to this day. But emptying of country districts must be a usual consequence of a population rise, not of a fall. The modern United States of America is an example.
In actual human practice, the first-order reason for driving peasants from the land was to enrich the landlords, but societies put up with the miserable injustice involved because the new ways were more productive; letting the landlords have their way yielded more food for the state, and if pushing even more people into the growing populations of the towns' displaced peasants, it at least promised bread for those growing populations. This is the argument of our "green revolution," an argument that has been used as long as there have been civilized states. "The people must be fed; farm the land efficiently for the benefit of dense settlements."(pp. 100-101)
As a society becomes wealthier through trade and conquest, the citizens of that society prosper. Since there are more niches available to them, their numbers invariably increase, since people still have the number of children they think they can afford. Rising living standards and hope mean rising populations, again more for the poor than for wealthy, since the wealthy demand more resources to raise their children and are accustomed to a higher standard of living. In fact, many of the highest upper-class patrician Roman families died out because they did not have enough offspring to sustain themselves. The "golden age" of Antonine emperors from Hadrian to Marcus Aurelius did not have biological sons to sustain themselves:
Yet at the very top of the social heap it is possible that a few families were small enough to be below the replacement rate. An intriguing suggestion of this lies in the fact that none of the Antonine emperors had sons to succeed them except the last. This was a very fortunate circumstance for Rome, because these men then adopted sons to be their successors, choosing boys for their quality to be emperors themselves one day. It was probably this circumstance that gave Rome its precious hundred years of stable government in Antonine time. The good years ended when the wise Marcus Aurelius most unwisely left the Empire in the custody of a real but quite unfitted son, Commodus. (p. 163)
Associative mating, where rich people marry exclusively other rich people, consolidating wealth in the upper class niches, becomes more common as well. But despite it all, the numbers will keep on rising.

A final strategy after oppression, caste systems, colonization and foreign trade, is simply seizing the lands of your immediate neighbors by aggressive war. We saw this already with Alexander the Great seizing the neighboring lands of Egypt and Persia. The situation was different for the Romans.

Unlike the lands to the east which had older, more complex, settled civilizations and large, crowded, urbanized populations, the lands of the barbarians were sparsely populated due to the barbarian's ways of making a living, and thus relatively empty from the Romans' point of view. The barbarians still lived in small, tribal, village-based societies, just as the Romans had once done. They had low population density and hence much individual freedom as a consequence. In fact, Roman writers wrote admiringly of the rugged independence, ferociousness and courage of the Celtic and Germanic barbarians they encountered.

Nonetheless, the superior military techniques of the Roman military machine were pressed into service to seize their lands and expand the Empire. Roman industry fled across the Alps from the areas of the Mediterranean depleted of forests and topsoil, and the barbarians were displaced by vast latifundia dedicated to feeding the urban masses:
When numbers and aspirations for broad niches continue to grow beyond what can be accommodated by trade, then the only expedient left is outright theft. A growing city-state will certainly find itself in a world peopled by others less citified and less densely populated. Very likely much land will be full of wandering herdspeople or nomadic farmers, ways of life that not support dense populations. It may even happen that citified people will find lands still occupied by hunter gatherers, as when Europe first thrust itself into North America. More often the surrounding lands will be inhabited by people whose ways of life the city folk had left behind them some generations before. What is certain, however, is that the neighboring land is, by the standards of the city, underused and undersettled. The city-state will be surrounded by cultures whose technology of extracting niche-space from the land is inferior to its own. Taking over this land is an obvious thing to do.
The ecological hypothesis predicts, therefore, that a society will engage in land theft when its organization and aspirations show it to be better able to extract a living from the surrounding lands than the people already there. And it follows that a society which has reached this position also has, and knows it has, the better weapons.
Land theft means planting a colony or annexing a whole territory. Both processes must be resisted by the people already there. But those of the civilization who covet the land have an advanced technology of war, inevitably, by reason of the technology and trade which has made them a city. When they begin armed emigrations, whether for colonies or for empire, they cannot be stopped. This is why nations like Rome or Greece built such glittering victories.(PP. 89-90)
This is also likely to be self-defeating, as eventually the empire can no longer expand. This may be because of technological limitations, or by running up against inhospitable environments or hostile natives who can use the landscape to their advantage, as the Romans found in Germany. Also, what often happens is that the neighboring peoples adopt the military weapons and techniques of their more powerful neighbors, which leads to a bloody stalemate as the parent society no longer has the superior technique. He uses the example of the Roman empire versus the Germanic barbarians and Sassanid Persians.

The Persians were the first to deploy heavily-armored cavalry for use in warfare. They were also early adopters of horse-mounted archers who were able to fire while retreating--the so-called "Parthian shot." The Eastern Roman Empire adopted the Persian heavy cavalry techniques as the Byzantine cataphract, allowing it to hold onto its territory. Eventually, the heavy cavalry of the cataphract was adopted in turn by the barbarian Goths, who used it to defeat the Byzantines at Adrianople. The use of heavy cavalry spread throughout the barbarian tribes, and was the basis of the medieval knight, who dominated warfare until the adoption of gunpowder.

Eventually, the barbarian tribes who seized North Africa from the decaying Roman Empire were overrun by another outsider barbarian group--the newly united tribes of Arabia under the banner of Islam. These mounted horsemen, accustomed to the techniques of banditry and raiding, swept out of the desert conquering everything until their path until they met the armored knights of Charles the Hammer in France and the Byzantine cataphracts of Leo in Turkey. These societies all expanded until they met others who had equal or superior military techniques to their own, whether invented or adopted. And they were all driven by expanding populations looking for niche space.
When the leading classes of a state have led their people through the stages of technical improvement in manufacture, a class hierarchy, trade and the colonial expropriation of land, they are coming to the end of the possibilities for finding more niche-spaces. Yet a society putting all these into effect is likely to be a buoyant one and its people are likely to be conditioned to the long success story. The breeding strategy, therefore, will certainly work to keep families relatively large. Each couple of the colonial state will choose its family in some hope, and this will be so in both parent city and daughter colony. This means that the succeeding generations will see more people still, not just starving poor but more particularly aspiring upper castes and classes. 
All that can now be done by the rulers to keep control is more of what has gone before, and this we must expect: more attempts at trade, more social ranking, more aggression. Aggression seems the most promising alternative.
Sending out a civilized army to take yet more undeveloped land is not only likely to succeed, but also exciting. And so niche theory suggests that a tide of aggression ought to flow out of the expanding state until a time comes when something stops the flood of armies; perhaps the distance of communications, perhaps reaching a boundary defended by some other army of almost comparable technique, perhaps a combination of both.
Aggression remains available as a solution to crowding in the more desirable niches only for as long as the weapons of the state are superior to the weapons of any people within reach. The aggressor state will always be both wealthy and wanting more wealth. Victory will always be achieved through superior technique...
We will find a similar pattern of events behind all the greater conquests of history. Aggressive conquest is to be expected whenever population and aspirations grow together. Up to now every advance of civilization has been accompanied by rising desires and rising numbers. Always this has resulted in aggressive war. Ecology's second social law may be written ''Aggressive war is caused by the continued growth of population in a relatively rich society." (emphasis in original) (PP. 91-93)
A crowded population with superior weapons and tactics seizes land from its neighbors. This creates more niche space. Aggressive wars become popular among the citizenry, and the society becomes militarized and warlike, lionizing their martial prowess and celebrating war and military victories. Aggressive war becomes a habit to nations that pursue it successfully. But in these victories is the seed of decay. The options are running out. Once the society is at its height, with plentiful niche space, all that is left is decline. New powers are on the horizon, and they have copied the techniques of the more successful societies, and perhaps even improved on them (the advantages of backwardness).

The society becomes sclerotic, and this leads to social conflict and decay. In the end, the Roman empire turned to incessant fighting and civil wars as disparate elites battled it out for niche space at the top, while the newcomer barbarians at the bottom of society, who required fewer resources than the native-born Romans, outbred them, even while adopting key elements of Roman culture. The empire was overrun by less dense, less sophisticated powers from outside as it lost a sense of common purpose. Eventually, population did decline, but only after the collapse.

Colinvaux dismisses the "spiritual/biological theories of history" which argue that a society goes into decline because it has a fixed lifespan just like an individual, or that societies decay because of  a sort of moral malaise, loss of spirit and vigor, or a failure to rise to certain challenges. Rather, it is the rise of population and an exhaustion of options for expanding niche space which leads to social conflict, and ultimately, collapse:
The combined expedients of better government, better technique, emigration and going to war can, of course, never produce more than a temporary relief from the pressures of demand. If numbers go on rising, the condition of the people, both leaders and led, will be as constrained as ever within a few generations at most. However large the empire built from underdeveloped lands, there has always been a finite limit set by logistics and geography. When all is full there is nowhere else to go.
Niche theory predicts, therefore, that a limit will be reached to the number of broader niches that can be found by ingenuity, trade and theft. And yet, the theory also predicts that the numbers desiring broad niches will continue to increase. The empire will become crowded for its upper classes. It is this phenomenon which is likely to be the cause of decay. Social unrest is now inevitable.
As the empire crowds, freedom of choice must be an early casualty. There has to be more government to allocate and control. Bureaucracy will be getting more complex, its practitioners more numerous. This is so inevitable a consequence of expansion that a minor ecological social law might be written, "All expansion causes bureaucracy."
But the bureaucrats cannot make more resources, they can only allocate what they have. Opportunity for betterment wanes, and initiative must wane with it. The army is no longer the pathway to a good life and will be neglected. After all, the only role soldiers have left is defense against distant barbarians. Once a fresh military power appears at the borders the empire must fall.
In the final days the empire may linger on if it can impose so stern a caste system that many families are held small by want. This is what some of the longer lasting civilizations such as Byzantium and India achieved. But this works only until other states catch up with the static weaponry of the moribund empire. Then comes destruction. The final set of predictions can be summarized, then, as:
  • Superior weapons will be used to expropriate land and to plant colonies.
  • All aggressive enterprises are undertaken with superior military technique and in a calculated manner.
  • Aggressive wars are launched by rich societies and come from the needs of the comparatively wealthy, not of the poor.
  • An elaborate bureaucracy and loss of freedom will always appear some generations after the establishment of empire by conquest.
  • Collapsing empires will have rigid caste hierarchies and stagnant military techniques.(PP. 93-94)
Colinvaux then compares his ecological theory of history against Toynbee's massive work, "A Study of History." He finds that it describes the observed historical pattern much better than Toynbee's own theories about spiritual decay, which Colinvaux sees as quasi-mystical not based in hard science.

In A Study of History, Toynbee charts the rise and fall of twenty-one distinct cultures he identifies*.  He distinguishes these civilizations based on their unique cultural, religious, spiritual, and artistic outlooks, and their economic, social, and political organizations. Toynbee attempts to identify a common pattern in the rise and fall of each of these civilizations.

He sees a harsh and unforgiving environment as the required crucible which presents certain challenges to a group of people. If these challenges are difficult enough, but not so harsh that they overwhelm a culture in its infancy, it forges a distinctive cultural "spirit" in that group of people. A society which overcomes the challenges presented to it formulates a distinctive mode of life:

A society, according to Toynbee, develops into a civilization when it is confronted with a challenge which it successfully meets in such a way as to lead it on to further challenges. The challenge may be a difficult climate, a new land, or a military confrontation (even being conquered). The challenge must not be so difficult as to be insurmountable or even so difficult that the society does not have sufficient human resources and energy to take on new challenges.
Rubbish, says Colinvaux; a better explanation is the ecological hypothesis.  A harsh and unforgiving environment doesn't make the "spirit" of a people stronger, it just means they run into ecological limits sooner due to population pressure. This pressure leads them to prey upon their immediate, weaker neighbors who have less dense populations, developing superior military techniques and discipline along the way. The harsh environment forces the people to be adaptable and hardy, and enforces internal social cohesion. The winners of these Darwinian conflicts inevitably expand, assimilating their neighbors through trade, conquest and colonization, exactly as Toynbee describes:
Civilizations arise in marginal lands; Toynbee says that people need the spiritual shock of a hard environment to give of their best. An ecologist is not surprised to learn that marginal lands foster aggressive civilizations, though less impressed by Toynbee's belief that the arousing of the spirit is what counts. It is in marginal lands that the pressure of rising numbers will be felt first, forcing expansionist zeal, the limits are reached sooner in marginal lands, habits must be changed sooner if want is to be avoided, and aggressive armies become an earlier requirement. Once the armies are made, the people of a marginal land only need a victim for their aggression, and a plump victim is always by definition waiting next door. (p. 98)
Toynbee describes a creative minority at the upper echelons of society whose activities and thought patterns animate the actions of the broad mass of people below them. The responses of the creative minority to challenges presented become worthy of emulation by the majority, and the society expands under the leadership of this creative minority:
Toynbee believes that the ideas and methods for meeting the challenges for a society come from a creative minority. The ideas and methods developed by the creative minority are copied by the majority. Thus there are two essential and separate steps in meeting a challenge: the generation of ideas and the imitation/adoption of those ideas by the majority. If either of those two processes ceases to function then the civilization breaks down.
Colinvaux would see such people as occupying the broad niches of a new society early on when the niches are relatively empty. According to Toynbee, this creative minority eventually hardens into a dominant minority who become ever more repressive over time. Colinvaux would say that it is when the niches at the top of society become filled that the creative minority ossifies into a "dominant minority, steadily becoming more oppressive over time due to increasing competition for niche space.

Toynbee claims that it is at this point that societies coalesce into what he describes as the dominant minority, an internal proletariat of citizens outside the ranks of the dominant minority but nevertheless members of that culture, and an external proletariat of people on the fringes of the society under its influence, but still distinct and separate from it.

The internal proletariat becomes ever more restless as opportunities dry up, and conflict ensues between the dominant majority and the internal proletariat as the former become more insular, repressive, and inward-looking. At this point, a society becomes increasingly destabilized, not from below, but from the ranks of the internal proletariat as the overproduction of elite aspirants necessarily means that upward mobility is limited. This leads a society-wide loss of faith in elites and social institutions, leading to what Toynbee terms a time of troubles:
If the creative minority fails to command the respect of the majority through the brilliance and rightness of their solutions to the problems and challenges of the society then the minority becomes merely a dominant minority. In the breakdown of a civilization the society splits into three parts: the dominant minority, the internal proletariat (the working masses which are part of the civilization) and the external proletariat (the masses which are influenced by the civilization but are not controlled by it.
Colinvaux would see this as the effects of crowding on the living standards of the upper classes of society, since they use the resources that the majority desires. As he describes, the people occupying the broad niches are the first to feel the effects of rising numbers, and they will become steadily more oppressive over time while establishing caste systems to assign people to the available narrow niches. The establishment of some sort of caste system leads to conflict between the frustrated, upwardly-mobile middle classes and the top--the dominant majority and the internal proletariat:
From then on, Toynbee's reconstruction is as predicted by the ecological hypothesis. There is, for a time, a "creative minority" of people whose example is willingly followed by the mass, but the "creative minority slowly changes to a repressive "dominant minority. The mass no longer emulates, becoming instead a sullen "internal proletariat." (pp. 98-99)
As Colinvaux describes, people will be driven from the land and into the cities as intensive agricultural techniques are employed to feed the growing numbers of people. This will cause the ranks of the internal proletariat to swell. There will also be broad discontent as wealth concentrates in the hands of the dominant minority:
From the time of troubles onward the population shifts within the state. There is a drift from the land as peasants are displaced in the interests of increased production...The surplus people of the countryside go to swell the ranks of Toynbee's "internal proletariat," already being bred in the cities. To these are added the inhabitants of conquered less-developed lands, driven in turn from their fields by civilized businessmen. Spent soldiers join them, their stipulated service over and their military usefulness gone.
So there always developed in the great cities of empires large and growing populations with very little to do except be house servants or formal slaves of that dominant minority which expanded to provide both the governors and the bureaucrats of the state. All could be given bread for a long time by improving the efficiency of agriculture, and by taking the new efficient method to the freshly conquered lands of the spreading empire, but each new advance of technology, or regiment, sends its own quota of exiles to the central city, there to join that breeding proletariat in, but not of, the culture of the times.  (pp. 100-102)
So far Toynbee's history goes as an ecologist would expect. Endless growing numbers both maintain poverty and give it such institutional form as slavery. The new technology which increases resources is never able to exceed the demands made upon it by ever more mouths, and its only real result is the closer herding of people, together with the growing bureaucracy needed to constrain them. Wars of conquest relieve matters, but only for a short time. When the victory has been truly great, then the numbers who can aspire and live in large niches is expanded for a while so that hope can flourish also. This is why conquering societies talk so much of freedom and liberty. But the increased living space must be filled quickly by the broad-niche "species" in society so that the hopes of succeeding generations must be curbed. Then the needs of an ever-growing proletariat must press upon even the large living space won by conquest. The only stability then is the short-lived one of people knowing their place. (p. 102)
The time of troubles is ultimately resolved by the absorption of the external proletariat into what Toynbee calls a universal state. The universal state is typically seen as the apotheosis of the civilization, but it is actually a sign of a civilization in its autumn years:
The disintegration of a civilization involves a time of troubles, such as a time of wars between the nations which are parts of the civilization. This time of troubles is followed by the establishment of a universal state, an empire. The existence of a universal state such as the Roman Empire is evidence that the civilization has broken down.
Colinvaux would see the establishment of a universal state as a logical response to the pressures of  crowding on the broader niches. The universal state is a way to create new, broad niche opportunities for the internal proletariat through colonization, trade, conquest and war. Indeed, we could say that all of these empires can be partially thought of as vast trading regimes with similar laws and institutions imposed from above by force to bring them about. Empires are necessary for vast trading regimes - The Roman Empire knitted together the Mediterranean region into one vast market; years later Genghis Khan's brutal rule would allow fruitful exchanges between Europe and China.

But once the universal state is established, even though the empire seems to be at its height, it is already decaying internally. The original culture has occupied distant lands; both the internal and external proletariats have expanded rapidly, and elites become increasingly isolated and take to warring among themselves and looting the underlying society, leading to a crisis of faith in institutions. Politicians become increasingly insular and self-serving, feathering their own nests while neglecting the common good. As people lose faith in the old order, they turn to new modes of life, often adopting new religions and cultural institutions in the process. The final sequence is:
Ultimately the universal state collapses and there follows an interregnum in which the internal proletariat creates a universal religion and the external proletariat becomes involved in a Volkerwanderung, a migration of peoples. 
The universal religion and its philosophy are usually borrowed from an alien civilization. The development of the new religion reflects an attempt by the people of the internal proletariat to escape the unbearable present by looking to the past, the future (utopias) and to other cultures for solutions. The religion eventually becomes the basis for the development of a new civilization. Religion amounts to a cultural glue which holds the civilization together. There is thus a close relationship between religions and civilizations.
Colinvaux describes it this way:
In the mechanisms of the times of trouble, which forge the internal proletariat and pave the way for the great captain and his armies, can be found some off the more revealing workings of ecological process. Not only do small crowded states war with each other, but capitalist business always emerges with all the social problems it brings in train. This is society trying to increase resources with improved technique, working to increase the size of the cake at home while its armies are fighting to increase it abroad...(p. 100)
But eventually, often after several generations of turmoil, a more able chieftain than the rest imposes his military will; the people gather thankfully behind the prospect of peace which he offers, yielding to him the instrument with which to establish an empire. The evolving civilization has culminated in a "universal state," and there may follow a protracted period, as under the Roman Empire, when an ordered society persists, the dominant minority remaining in charge, the mass constituting the "internal proletariat" consenting or collaborating in its bondage. But in the end the social order always decays. (p. 99)
The dominant minority is hard put to defend the boundaries of the empire against neighboring peoples and these evolve into a hostile alien force, the external proletariat. Finally, with the breakdown of order within, and the increasing hostility of the less disciplined but freer spirits from without, the empire crumbles leaving behind only traces of its culture and religion out of which those who have inherited its impoverished lands can begin again the process of invention and order.(p. 99)
Eventually, the means of war, colonies and trade expand to their greatest extent possible for the time. Caste systems are resisted by the restless and footloose masses clamoring for alternatives. The empire cannot accommodate them and disintegrates. Stagnation (stagflation) sets in. Population may finally start to decline, especially in crowded and filthy urban centers.

In the end, collapse is all but assured as the people inside the state turn on each other, leading to something that from outside looks like "moral decay." Social cohesion disintegrates and elite overproduction sews chaos:
But an empire always has an edge, at first diffuse and spreading, but later almost stationary. Its actual position is a function of contemporary technique in warfare, government and transport. Outside it live people whose kindred have been conquered, absorbed, oppressed, deported, or even slaughtered by soldiers of the civilized state. The survivors beyond the pale have learned something of the civilization's technique in fighting, and have also learned to lead mobile lives, so that they may avoid forays of the empire's soldiers...A whole new way of life, a new niche, has thus been developed in response to the pressure of the empire's people. Footloose, self-sufficient, partly nomadic, warlike; it is a way of life which often seems admirable to the imperial governors who confront it...Toynbee finds such people living on the boundaries of all the civilizations he studies, calls them the "external proletariat," admires them, and tells us that they have in common the writing of epic poetry. (pp. 102-103)
In Toynbee's account the war bands of the external proletariat are eventually to cut their way into the dying empire, hastening its fall...An external proletariat, forged from people who do not care to live in cities but who must run from a civilization's soldiers, is, with the knowledge of hindsight, a plausible outcome of the building of an empire...once the external proletariat has perfected the new way of life its own numbers will tend to rise, forcing it always to look for more resources both to safeguard children from want and to apportion among its younger sons. Trained to war by their way of life and equipped with some of the military techniques borrowed from the empire, their obvious expediency becomes armed raids across the borders. Their pressures on the empire must grow as their numbers rise, and an empire steadily weakened by the pressure of its own miserable masses finds itself ever more strongly attacked by armed young men from outside.(pp. 103-104)
Outside the gates of the civilization, a new culture is expanding, selectively adopting the successful methods of commerce and warfare developed by the dominant culture. The external proletariat are accustomed to living with less, so their birthrate is higher. They are more self-sufficient, not being able to rely upon the vast trading network forged by the dominant society's elites. As the dominant society's wealth concentrates in the hands of the sclerotic dominant majority, and the internal proletariat's numbers decline even as those of the external proletariat rise.

These trends culminate in a new civilization which arises out of the ashes of the old, either from outside it, or from within the crumbling society itself. New challenges are confronted, and a new creative minority emerges from the external proletariat. The cycle begins again.

This is similar to Ibn Khaldun's analysis of the thirteenth-century Maghreb, with nomadic peoples (the "external proletariat") who have been oppressed by the primary culture and having a greater sense of social solidarity and cohesion (asabiyah), eventually able to defeat their oppressors. Their greater sense of social cohesion allows them to conquer and assimilate the settled urbanized civilizations which have fallen into decay.

At the height of the empire, after a period of stability a collapse is all but assured in the twilight of a fading civilization:
The fading summer of each of Toynbee's civilizations passes with the muted mutter of dissension in thee big cities and ceaseless petty war at the frontier. But, at last, government crumbles at home, and war bands from outside swell over the disintegrating mass, Toynbee draws lessons of the spirit from these events, looking for the prime causes in the class war, the failing vigor of a privileged minority and the social injustice of commercial exploitation at home, contrasted with the ennobling experience of the external proletariat, which left it independent and tough.
Moral virtue then triumphs over moral decay and the lands of the empire are inherited by new peoples who proceed to build a new civilization on its ruins. No doubt these events do strange things to the human spirit, but their prime cause is not spiritual; it is an animal breeding strategy applied to human affairs. All of what Toynbee sees is predicted by the ecological hypothesis; all is the inevitable consequence of trying to provide a better life for ever increasing numbers of people. (p. 104)
Those were Toynbee's conclusions on the rise and fall of all the twenty-one major civilizations that he thought he could recognize from a long perusal of history. The creative minority, the successor dominant minority, the time of troubles which ushers in the succession, the internal proletariat, the emerging conqueror or great captain whom Toynbee sometimes calls a "saviour with a sword," the universal state that he builds, and the long autumn of order while the state endures as a stable thing with all knowing their place—are all events predicted by the ecological hypothesis.(pp. 99-100)
For example, in the case of ancient Rome, once expansion was no longer possible, declining social mobility, increasing poverty and despair, a loss of the tax base, a brutal police state, economic failure and stagnation, low growth, internecine warfare among elites, political corruption and sycophancy, futile, open-ended wars, and social decay followed. These are all symptomatic of a culture in decay. The culture can no longer rise to the challenges presented to it:
Yet, for all the peace and stability of the Antonine years, there was much about life in the empire which was far from admirable. There was a rigid caste system, with a social pyramid which grew ever steeper despite changes at the top as more provincial people were given Roman citizenship. The gap between rich and poor was desperately wide, and growing wider. Slaves could still be treated with a ferocity almost incomprehensible to people of our day. Growing masses of the urban poor lived without work, in disgusting tenements, on welfare payments of grain and entertained by horrible murders of prisoners and beasts in the public arenas built in every city for this necessary purpose.

Recession showed up as a chronic failure of tax revenue. Roman governors were always hard put to pay and equip their soldiers, and they had to meet even increasing expenses to keep the mass of the people in the city tenements from rebellion by giving them free food. In the last century they actually had to meet the expenses of a true police state, paying out a network of spies and informers...The emperors resorted to the Roman equivalent of printing money. They debased the coinage, mixing cheaper metal in gold and silver and declaring that the new coins had the same value as the old. Our modern governments push out paper and call it "wealth"; the Romans pushed out base metal and called it "wealth"; and the result was the same...Emperors tried wage and price controls, backing them up with brutal threats...but it did not work. They succeeded only in ruining the middle class. At the top of the social pyramid the depressed economy made government difficult. For the mass of people in the lower castes it made the chance for betterment hopeless. (pp. 156-158)
What was left to the Roman rulers was repression, and they learned to apply that solution very well. Indeed, repression was forced on them early, of course, as they enslaved their world with swords, javelins and terror. The old Roman Republic bequeathed to the Empire a state already based on slavery, repression and fear. Early reliance on social force actually helped bring about the very failure of technique which required that growing populations be held down by more force still, because a slave society of the massively poor is not likely to be technically ingenious—for why make a machine when there is cheap muscle to do the work? Romans came very close to real industry, needing, for instance, only the slightest advance to produce steam engines, but no Roman made the small tricks of invention necessary. The repressive social system stopped them by requiring slaves, and the social system itself had to be made more repressive still by default of invention. 
Social repression in the late empire tells us that the Roman possessions were crowded, as indeed they were. All the niche-space winnable by conquest, trade and slave-based industry had run out. If you were middle class or better, your children could only hope to live as well as you by elbowing someone else's children. This is real crowding in the ecological sense; all niche-spaces filled and the numbers still coming. Low population densities in parts of the Empire make no difference to this conclusion. (p. 166)
"Recession" is not really the right word to use for these failures of the Roman economy, however, because there was growth. The Romans seem never to have stopped building  roads and aqueducts and cities, nor did they fail to make weapons for armies which grew continually larger. But the growth was painfully slow. It was steady progress, not recession, even if slow enough to look like stagnation to us. But the slowness had the fatal consequence of never producing a surplus of capital to invest... (p. 158)
Then came strong-man rule. It was achieved by a series of military despots, men like Severus (that first emperor of African and possible Carthaginian descent), Diocletian and Constantine, who had a genius for the imposing of order by tyrannical force. They made a police state out of the empire. 
The smell of the police state comes down to us very clearly from the century preceding Constantine when Rome held its last sway in united government as one state under one ruler. Soldiers ruled; and feeding armies without payment became a first task of those living where the legions were stationed. Taxes increased and the bureaucracy became ever more complex. The social pyramid grew even steeper, developing into a caste system rigid perhaps beyond a real understanding. You risked your life if you spoke unconventional thoughts. Spies and informers were so prevalent that it was sometimes dangerous to talk in public at all. (p. 159)

Then came renewed troubles and the final, fatal wars. The Empire which had been built by force and together by force, was finally destroyed by force; real alien force brought in by armies from outside. The Empire from the time of its wealth, therefore, went through a stable century, wars of military adventurers, a triumph of despotism, and eventual subjugation by foreign foes. In outline, this history sounds very like the general predictions of the ecological hypothesis; in detail the fit seems even better. (pp. 159-160)
Sound familiar?

One element that is especially fascinating in both analyses is how rising numbers bring about a change in the spiritual outlook of a people. While some have speculated that increasing wealth was a cause of the emergence of moralizing religions, in Colinvaux's thesis it is the rising poverty caused by excess numbers which brought about the distinctive character of the Axial Age religions which gave people the coping skills to learn to live with increasing poverty, misery, and low class mobility.

Unlike the earlier dominant pantheons dedicated to the martial virtues of a confident, expanding, cohesive culture, these new religions all preached the same basic things: that life is full of suffering; the poor will always be with you; you should care for the sick, elderly and vulnerable; you should accept your lot in life with resignation and make the best of it; you will live in ease and comfort in the next life as opposed to this one; and so on. Such religions teach people how to be joyful in the face of despair.
In the end Toynbee notes that a world religion rises from the oppressed proletariat and persists long after the empire has fallen. He claims that all the major  religions of the world arose in this way; they started as religions of those subjugated in empires. Ours of the West was one, built out of conquered people desperate under the exactions of Roman military rule. Ecologists can easily understand the form these religions take. Much of the appeal of proletarian world religions lies in their counsel to the oppressed to endure. Nothing can be done; the poor are with us always; rely on your spiritual strength and make the best of things. For the crowded masses, to whom Jesus, Buddha, Confucius, and their like appealed, there was, no hope for an improvement in the standard of life. People knew in their bones that the lives of their children would be no better than their own lives. They did not know that the reason for this was the swelling numbers of people who used up new resources as fast as they could be created, but they truly knew the outcome all the same. So, by the device of a new religion, crowded, poor, citified people have always turned to the plastic properties of the human spirit, learning to be happy with very little. People learn to live in very narrow niches when religion teaches, and world religion is but another expression of learning the necessities of life by the process of taboo.
It is fascinating to note that India, long the most crowded of civilizations with an extreme caste system, developed some of the most sophisticated systems of spiritual development ever seen. Eastern mystery cults emerged in the decaying Roman empire, with one of them--Christianity--emerging as the dominant cultural factor in post-Roman society. Islam replaced disparate nomadic tribal gods and preached peaceful submission and care for the poor. Buddhism taught people to cope with falling living standards by turning inward. All of them forbade usury and preached care for the poor and downtrodden, such as the giving of alms and Zakat. All of them also depersonalize nature and exalt man. Perhaps the dominance of these religions has much to do with their ability to help people cope with the suffering caused by the effects of overcrowding in a world where the population is expanding geometrically. Is it any wonder we see the rise of religious fundamentalism in places like the Middle East and the United States as the economy decays and the hope for a better life is thwarted for the majority of people?

It's interesting to view the above procession against what we normally conceive of as collapse. Collapse is often seen as a fairly linear process, but the above shows that there will be a variety of responses by the elites of society, which will prolong the inevitable. There are many methods that a society has at its disposal to keep itself propped up and to keep conflict from boiling over, and these are fairly predictable. The nature of these responses are described by both Toynbee and Colinvaux. It is also important to note that collapse is assured when the empire is at its height, not on the way up.

Yet the measures - free trade, migration, wars, new technology, and so on, are seen as permanent solution to problems, when in reality they are only stopgap measures employed by desperate societies in their autumn years. The kick-the-can measures only mean that the problems will eventually reconstitute themselves down the line in a more intense crisis. Eventually, a reckoning is due, but the process toward that resolution is jagged and complex, and often hard to discern against the noise of daily life.

  After outlining his ecological theory of history and making the comparisons with Toynbee, the central portion of the book is dedicated to applying the ecological hypothesis to various episodes in world history.

The longest of these is what Colinvaux calls the "Mediterranean episode." He gives this as approximately the flourishing of Greek civilization and the conquest of Alexander the Great, through the rise of Rome and the Punic wars, through the collapse of the Roman Empire and the partitioning of its former lands between the Christian barbarian kingdoms, the Islamic caliphates, and a remnant of the Eastern Roman empire.

I've already alluded to many of Colinvaux's insights in previous entries, but a few points are worth mentioning (all emphasis mine). The beginnings of the Mediterranean episode come from settling down into urbanized village life:

The immediate effect of switching, even gradually, from barbarism to a settled city life is that the population grows. The new economy produces more food, the new niche permits people to be content when living more closely packed, each couple can raise more children and does so, and the numbers of people steadily increase. So it was in Greece.

The ecological hypothesis predicts that this process will lead to colonial enterprise, to trade, to much fighting, to an oppressed proletariat, to high technology in war, and to the creation of empire by military means as a popular goal. The written history of Greece shows how each of these things came about, and even reveals that the Greeks knew something of what was happening to them. (p.114)
On the effects of Greek geography and culture on their war-making ability:
The pattern of  these various consequences of rising numbers and changing niche in Greece was influenced strongly by Greek geography. The land is both mountainous and dissected by embayments of the sea. This meant that scattered city states could grow in a partial isolation from each other, having defensible state boundaries and well limited patches of local resource. It may well have been this isolation of each Greek city-state that helped to foster the refinement of their remarkable military hardware, protracting wars between neighbors, letting victories be indecisive so that return engagements could follow after a few years spent in perfecting armament. Certainly it is true that the first and most fundamental of civilized fighting forms, the armored phalanx, was better refined in Greece than in any nation of which we have record.(pp. 114-115)
Highly civilized weaponry was a fact of life to free Greek citizens. Every independent man owned the weapons of hoplite infantry and knew how to use them. His own money equipped him for war. He could be "called to the colors" at any time, and he went willingly. Front line soldiering was both the duty and the privilege of the substantial citizen, and the poorer classes went to war merely in his support. The better-off fought; the less-well-off supported. And this was reasonable, because the colonies and trade on which the high standards of life of the wealthy in a Greek city depended could be guaranteed only with expensive weapons. (p. 118)
The Greeks responded by colonizing the Mediterranean; "like frogs around a pond" according to Plato's description:
Each of the major city-states of Greece sent out colonists to found tributary cities elsewhere; scattered round the coasts of the Persian dominions, in North Africa, in Sicily and beyond. This was how local city states, each pressed into an ancestral valley of the rugged Greek terrain, had found opportunity for businessmen and adventurers alike. ...The people of Athens could find more niche-space for the Athenian way of life by building colonies which would duplicate Athenian ways, and they did so.
The state of Athens grew through colonies and trade in a somewhat different way. The land was not lastingly fertile, like the island of the Chalcidians, having soils which were easily denuded by agriculture. Ecologists know well the Mediterranean soils, like those of Attica where Athens was built, and the story they have to tell. They are now red, being given the name of "terra rosa." This is the red of minerals weathered under a mild climate. But once, in their forested antiquity, the soils were probably brown, because they were well mixed with the humus and leaf litter of the forest above. Good agricultural soils need such an admixture of humus. But the people of Attica cleared the forests, burned off the brush, plowed the land, took away the crops to eat in their villages, and let the burning sun of the Mediterranean dry the soils so that wind and water could sweep the humus away. The fertile brown color went, and the unproductive red mineral mass of the terra rosa remained. This was the result of the first intensive agriculture in Attica, and the Greeks themselves understood the cause. A sentence in Plato reads, "all the rich, soft soil has molted away, leaving a country of skin and bones."

But the poorness of the soils of Attica seemed to have helped the trading side of colonial life to grow with particular energy. Athenian men of business concentrated on taking from their own land only what it would yield easily, which happened to be olive oil and silver, and they proceeded to build ships so that they could trade these commodities for the other things they needed. There was no living for farmers any more, except for the few who tended the olive trees, because the people's grain was now grown by barbarians in the Ukraine, and the people had to crowd near the granaries in Athens and become the servants of manufacture. There were now rich and poor in Attica as there had never been before. (pp. 119-121)
In addition to colonization and trade, there was also military conquest, both as a way of increasing niche space and of controlling population growth. The most celebrated practitioner of this was Sparta:
In addition to colonies and trade as answers to the needs of growing numbers, there is the expedient of direct conquest and elimination of neighbors. In a nation which had invented such a clinically effective instrument of compulsion as the phalanx, this expedient was sure to be tried, and it was. The most celebrated exponent of this art of neighborly aggression was Sparta. But aggression on neighbors meant fighting other Greeks who also knew the effectiveness of lines of armored spearmen. Spartans could not have the technical superiority over fellow Greeks which made it so easy to force other nations to yield for Greek colonies, and had to develop a society organized around the needs for absolute military efficiency in order to prevail. (p. 121)
About those Spartans:
Spartan discipline is legendary. But it is important to note that it was the well born youths who were trained to this asceticism in war. In battle, the hoplite shield wall held by young men of good Spartan families was supported in the rear by up to eight ranks of helots, or slaves, who passed forward spare weapons. It was this perfection of armored warfare from Sparta against which Herodotus tells us the Persian waves of infantry broke at Plataea, and it was this philosophy of war which drove Leonidas to make his last stand with the three hundred All this Spartan excellence in war was clearly and directly the achievement of the ruling class and in its own interest.  
Both the Spartan military society and the commercial society of Athens worked by compressing the niches of the mass; specialized labor was needed, often dull, repetitive, mechanical, soulless labor. It must be performed by people whose ancestors, only a few generations back, were free farmers; and in a world where free, farming, barbarian societies still existed on all sides. Freedom beckoned in memory and by example. So the proper functioning of the state required compulsion. The poverty of people with compressed lives, which is always the result of letting populations rise to soak up the resources released by new technology or conquest, took on the special institutionalized form of slavery. A slave was merely a poor man made to keep quiet about his inevitable lot by physical coercion. (pp. 121-122)
All of this meant that the Greeks were both pressed by the weight of numbers, and had developed the superior techniques in warfare that allowed them to dominate their neighbors:
The Greek city states had already, by the time of the Persian wars, found themselves in another of the dilemmas of growing numbers and ambition—depopulation of the countryside at the same time that the towns became crowded. This is a normal consequence of growth...As people better themselves by the trade and industry of the city, so it often happens that the city comes to support itself on the products of that trade. It may well be that the city even comes to meet its basic needs, as for food, from regions other than its own original hinterland. 
This will be particularly so if the city begins to trade with fertile agricultural states whose lower standards of living let them sell food to the city cheaply. The result is neglect of the ancestral countryside and an even more rapid drift of the country people into the cities...The Greek historian Thucydides saw the working of this process when he noted that Athens and Corinth were "crowded" and had to feed their people with grain imported from the Ukraine. Notice that he was not using the word "crowded" to connote wretchedness, for he thought of all the well-to-do people of these very great cities as part of the crowd. The people were living on Ukrainian land which fed them, and on all the coasts with which they traded, so they had ample resources, though "crowded." 
Interestingly, Thucydides did not think Sparta to be "crowded" in this way, though he notes that the Spartans did import their food from Sicily. Sparta's land empire apparently left its people less densely concentrated, though she too was living on the produce of other people's real estate.  
So the individual city-states of Greece each grew out of barbarism through settlement, manufacture, trade, colonies and dense concentrations of urban people to an eventual dependence on imported food for the large numbers of their proletariat even as predicted by the ecological hypothesis. The wealthier ranks of their societies took to war as they tried to expand and defend their broad niches, and they invented advanced techniques of fighting, particularly stressing body armor. They formed confederations of cities to meet attacks from the powerful, especially when their expansions into Asia provoked attacks by imperial Persian armies. The hypothesis predicts next that increasing demands made upon each city government would result in such wars that the different parts of the growing nation will come under strong central rule and loose its armies toward imperial conquests of its own. All this was about to happen.(pp. 122-124)
These were the conquests of Alexander the Great, which we have already covered. The Greek peoples took that huge population and military superiority, and used it to defeat the Persian Empire, establishing a world empire in the process (other Greeks such as Croesus of Lydia, who invented coinage, had made earlier failed attempts).

Indeed, before the Mediterranean episode, we could speak of the "Near Eastern Episode" which arose from the beginnings of agriculture in the Fertile Crescent, and included the first empires such as the Sumerians and Akkadians, the Assyrians, the Babylonians, the Egyptians, the Hittites, the Hyksos, the Phoenicians, and finally the Medes and the Persians whom Alexander conquered. It would have been nice to analyze these empires from the point of view of the ecological hypothesis. Interestingly, Toynbee notes that Egypt managed to survive culturally for so long by the "fossilization" of their culture. Also worth noting is the flooding of the Nile as a protection against erosion, something that was not possible in the Near East (where floods did not coincide with planting), Greece, or North Africa (which needed to be heavily irrigated).

Meanwhile, the agricultural villages of the Italian peninsula were moving in their own direction:
Civilization was progressing in Italy, no less than in Greece, but it was influenced by the long secluded shape of Italy. There was no scarcity of good agricultural land in this long peninsula, so the Italians had less need to turn to the sea for trade or conquest. Populations could grow for a long time with no more than the local adjustment of borders between tribal states. Then the states which deemed themselves the most worthy resorted to the usual armed aggression against their immediate neighbors. Techniques of land warfare were developed early and earnestly; the primitive infantry phalanx of armored spearmen probably appeared in Italy as early as it had appeared in Greece, and when Italian fought Italian it was to jab this deadly instrument against another equally deadly. And yet the military evolution of Italy went neither in the direction of the Spartan absolute expertise in conventional war to the ultimate development of the phalanx into the terrible instrument of Macedon, but into something quite different, the legion. (p. 131)
The legion proved to be the decisive military weapon in establishing the Roman empire. The major rival to Rome in the Mediterranean theater was thassalocracy of Carthage, founded by the Phoenicians. Like any trading regime, they had developed expertise in war. Yet hemmed in on the coast of North Africa, with vast deserts to the interior, they developed along different lines than Rome. Colinvaux's insights on the development of Carthaginian civilization and the wars are particularly interesting:
Carthage was in a fertile place, but there was not much of it. The people could not win more resources by aggression on neighbors, for the neighbors held only desert. Instead, the Carthaginians took the approach of the green revolution, terracing and irrigating the land they had, making their narrow strip between the desert and the sea so green with crops that it was eventually to be the marvel of Roman visitors. 
But when their growing civilization needed more opportunity, a broader niche for the more enterprising, there was no way of meeting the need in their narrow patch of land. Logic says that trade and then colonies were the only practicable ways to provide for Carthage an expanded way of life. We know that these solutions were, in fact, used to the extent that they became a national way of life. The Carthaginians lived by trade westward, where there seem to have been few trade rivals, leaving their mark round Africa almost as far as the equator, and round Spain to reach northern Europe. And they planted colonies in barbarian lands as the Greek cities did.  
But they did not develop an advanced technology of war. Carthaginians had few civilized states with which to fight, none alongside their home city, few near the barbarian lands which they expropriated for colonies. Good weapons, good armor, good courage, and the shield-wall approach of the primitive phalanx were all that were needed to secure the colonial lands of their earlier expansion. Carthaginians were not tried by earlier expansion. Carthaginians were not tried by civil war early enough to force them to give pride of place to military technology as the Greeks and Romans had had to do. Carthage had fine fleets, as befitted a trading state, but an indifferent army. When the real ecological wars came, this was to be her undoing.
So we have a nation of ambitious merchants and ebullient seamen, of wealth from trade to patronize arts and material things, of high consumption, of safe, confident, well-fed families. The numbers of people in this nation must surely grow, nor will the new sons be content with less than what their parents had. The Carthaginians were going to feel the need for yet more land overseas. We have no state statistics, no census, to tell us that the Carthaginian numbers did grow, but there is evidence enough that they must have grown in what the Carthaginians did: trade, colonies, and, at the last, outright attempts at foreign conquest. It was then that their vital interests first clashed with those of Rome.  
Roman authors, and our school books, tell the tale of these wars as a struggle to see which state should be mistress of the world; Rome, with all Italy already in its power, or the trading city of Carthage, sweeping the Mediterranean Sea with merchants and fleets. Rome did indeed go on to conquer and enslave every nation within reach of its terrible legions. But the war was not over who should be "mistress." It was a struggle for raw survival by the civilized folk of a trading state against the resources and weapons of a continental power. I suggest that the good guys lost. (pp. 135-137)
We know what happened next as the three Punic Wars for control of the Mediterranean:
Then were to be fought three great wars; Punic Wars as the Roman authors call them. The first was a long war of attrition over the ownership of colonial lands. In the second war, Hannibal crossed the Alps with his elephants, and the third war ended with the annihilation of the Carthaginian state and people.(p. 137)
Once Carthage was defeated, its land and possessions, including the silver mines in Spain. came under the possession of the Romans. The Roman war machine, forged during those Punic wars, allowed it to expand and take over the previous empires and run the entire Mediterranean was a giant free trade zone, creating plentiful niche space for their people:
Once the Italians under Roman government had taken Sicily, and all that had belonged to Carthage, they must have had all the land and resources which their people would need for several generations. Circumstantial evidence supports this. It became Roman policy, for instance, to settle their veteran soldiers with their families on farms in various parts of Italy; a tactic useful to Rome because it helped forestall possible rebellion from former enemy city states, as well as contenting such potentially dangerous citizens as veteran soldiers.  
But it also suggests that there was land to spare for making new farms; the population had not yet expanded to fill up the space made available by conquest of barbarian lands. Yet social habits do not easily change. The free citizens of Rome, which meant the rulers and the middle class of a slave-owning state, had created an army and invented an unbeatable military technique because they needed to go to war to support their standard of life. Now the need was, for a time, assuaged. But the instrument was made and the habits for war were made too. Foreign wars had proved an excellent way of finding opportunity for Roman rulers, soldiers and merchants; they gave promise to the younger sons. War also made the proletariat happy with glory and loot, and it brought regular supplies of slaves to support middle class living, as well as plunder, which could be taxed. War was the great provider of niche-space to those in power at Rome; this is the explanation for the rapidity of the Roman conquests of all the Mediterranean lands which was to follow. (p. 151)
Aggressive war became a way of life, and the Roman Empire seemed to be eternal to the people living under it:
Carried on by the weight of tradition, which now decreed that aggressive war was a way of Roman life, the unbeatably deadly legions were then thrust in all directions as far as they could be supported by the logistic techniques and the communications of the times. It took only a matter of decades to do this until the Roman Empire, as we Know it on the maps, was made. 
These immense possessions stolen for the Roman people by the legions now gave extraordinary possibilities for the Roman way of life. Much of the Empire, the whole of what is now France for instance, had been used only for barbarian living, a pleasant enough way of life but one which ensured that populations would be much lower than could be sustained from city granaries and advanced agriculture. Here was room for the younger sons to found new estates of their own; there was land to be made into farms for old soldiers back from the wars. Even with a bounding birth rate, it would be some generations before the pinch of land hunger would be felt. The Roman niche could broaden and the Roman numbers could grow for some time without serious consequence or worry. This is the fundamental reason why the Roman Empire lasted so long. The Romans were more fortunate than the Greeks of Alexander's day who had used their military superiority only to conquer filled-up civilized lands, where there was little room to expand.  
But Rome owned this vast territory only because her field army was unbeatable by any military force then in existence. Alexander had been able to spread the Greek way of life among the people he conquered because their experience of earlier civilization told them it was good. But the city ways did not seem good to free barbarians bludgeoned into the Roman state. The expanding Romans of the expanding Roman niche took away the means for barbarian living, as surely as the European farmers of North America made it impossible for an American Indian to live a stone age life. Again and again, people driven to despair turned on the occupiers, even though it always meant they would be butchered by a legion in the end. And the turmoil, in great possessions held only by force, meant that the Romans had to leave their government to those who wielded the military power. Via civil war and temporary arrangements the once free Roman constitution fell, as it had to, beneath central dictatorship.  (pp. 152-154)
Everywhere the power of irresistible military force prevailed until at last there came an imposed and universal peace in the lands round the Mediterranean Sea, and it happened that a succession of clever and well-meaning men, the Antonines, became emperors of Rome. Under the Antonines Rome entered what is said to have been a golden age, a time of flourishing prosperity and universal order, a time to which many historians still look back with a longing tinged with nostalgia. 
The lands round the Mediterranean Sea were set apart from the rest of the world by a ring of legions, who stood to their frontier posts like a dike restraining the stormy sea of barbarians outside. And, within the dike, there was a common law, a common currency, straight, paved roads, a central waterway free from pirates, and a system of banks and credits which let commerce, industry and agriculture flourish. It seemed to citizens of those times, as it seems to citizens of the modern prosperous States of the West, that the way had been found to the perpetuation, and even improvement, of the good life for all forever. (pp. 155-156)
We already covered some of the signs of collapse dictated by the ecological hypothesis - increasing bureaucracy, increasing taxes on the middle class, budget deficits, imperial overreach, elite overproduction and jockeying for power, stagnant living standards for the majority, depopulation of the countryside, urbanization, restlessness, distraction via welfare and entertainment industries (bread and circuses), political repression and a police state, inflation, debasing the currency, shortages of basic goods, political corruption and self-serving behavior, privatization of the commons, massive gaps between rich and poor, lack of social mobility, establishment of caste systems, civil wars, mass immigration, and so forth:
And so I offer a new explanation for the decline and fall of the Roman Empire. Resources that could be extracted by contemporary technique from the lands the Empire held were not sufficient to offer the broad niche of the middle-class life of a Mediterranean city-state to very many. Rising numbers held within the Empire in cities were a drain on what little economic surplus the Empire could produce, both from the direct needs of welfare payments and from the costs of the police apparatus needed to control these masses in poverty. There was neither the hope nor the surplus wealth needed for a large army of high-technology soldiers, as there had been in the days of the old Greek and Roman republics when the expansion started. The defenses of the long frontiers faltered and then distant peoples, needing land rather than civilization, pressed their war bands equipped with contemporary armament into the border provinces.  
Although the Empire of the West was struck down by force of arms in this way, the real defeat can still be read in terms of breeding strategy, numbers, and niche. The growth of Greek and Roman city-states into an empire was fueled by expanding niche and the promise of more. The resulting empire filled with people until the promise of expanding niche could not be met—a direct consequence of the Roman failure to develop techniques which could extract resources fast enough to provide large niches for many. In this sense, the Empire was crowded, and the fact that there were thinly settled provinces is irrelevant. Having relapsed into a police state with very high maintenance costs, the Empire found it hard to defend itself. And it fell.
As the Roman empire declined, the barbarians, needing new land came and took it over:
With the Roman power gone, the Gothic tribes spread into every country on the European side of the Mediterranean. Some even crossed into Africa. They came with their wives and children to stay, a mass migration of people, for they were under the pressure of crowding in their traditional lands. These traditional lands, in turn, were being pressed upon by other overcrowded barbaric and nomadic peoples from the central Asian steppes. The need for land by these technocratic Gothic barbarians in the suits of armor was apparently overwhelmingly great and they found it in the territories which had once been Roman. 
They found some land thinly populated because abandoned in strife, or because it was awkwardly placed to supply the needs of cities. Other lands had few people because given over to cattle raising, which needs only a small local population of animal caretakers. The really good farmlands were organized to feed distant cities and so were lived on by populations much smaller than those they actually fed. All these lands the barbarians could settle and use directly, leaving the Roman townsfolk to privation. (pp. 175-177)
The empty and depopulated lands of the former Roman Empire were ripe for the picking by the new peoples of the frontier:
The barbarians had come to live in a barbaric way, but they found that they had conquered countries laid out for the life of settled agriculture, and with fine buildings which it was sometimes tempting to use. For generations their ancestors had been able to see what Rome had, and sometimes to plunder a little of it for themselves. Now all was theirs. They began to settle on their conquests rather than to wander around them. And they had, from the start, to fight to keep what they had won lest it be taken from them by other barbarians, like the Huns, pressing on their heels from a population crush in the steppes to the east. Their armored horsemen found themselves defending the very lines which the legions had once held. And behind the new dike of mailed horsemen they began forging the Christian and feudal kingdoms out of which were to grow the modern civilization of the West.  
But in North Africa things were very different. The fertile grain fields which had once fed the city of Rome were but patches of land on the edge of vast and unproductive deserts. And in the deserts and semideserts in a great arc of land, from the edge of the empire in Asia to the Atlantic Ocean, were the wandering barbarian tribes who had always lived there. These people had pressed hard upon their resources since long Carthage, and their ways of life had changed very little. They were always warlike, because the necessities for life were so scarce that they must ever be ready to defend what they had. But they had never been able to develop anything like the formidable weaponry of the barbarians north of Rome, nor, indeed, any military technology beyond that suited for the swift raid across the desert.  
They traveled light on nimble horses, without armor, and fought in swift onslaughts when the blood was up, with lances and swords. They had never been able to stand against the regular soldiers of Rome, or Carthage before her, though they had been a nuisance to both states and had also sometimes been employed by both as auxiliary cavalry, They seemed in no condition to do with the Roman Empire of the south what the armored Gothic barbarians had done to the Roman Empire of the north. Yet the crowding of some of these people into wretchedness in the country of Arabia was preparing the way for fresh aggressive wars of conquest with results no less remarkable.  (pp. 179-180)
The eruption of warriors from the desert, which Muhammad uncorked like a genie from his Arabian bottle, was yet another of the wars of aggression started because the people needed land. There seems to have been no new military technology behind this aggression; the faithful merely fought as clouds of gallant horsemen, as they had always done. But then there was no longer a phalanx or a legion in North Africa to withstand them. As the Arabians began to succeed, the tribes of all the deserts joined them, with what perhaps may be best described as holy glee. The Christian populous societies of the fertile patches along the coast had not the spirit, or the organized purpose, to stand against this deliberate fury. They were conquered, oppressed, enslaved, and sometimes subjected to that final solution of "being driven out." Their onetime resources went to support the swelling numbers and swelling desires of the people who had embraced this new niche called "Islam." In about a century all the former African possessions of Rome were in the power, and under the command, of the once barbarians of the desert, who were taking over the settlements in their own way and building from them an entirely new civilization.  (pp. 181-182)
After Leo had defended Constantinople and Charles had defended France, the Mediterranean Sea became a division between the Moslem peoples of North Africa and the Christian peoples of Europe. Both civilizations were to develop in their own way, and although they were often to fight one another, the essential boundary between their lands was never changed. The peoples round that land-locked sea would never again be linked by common laws and common languages. The Mediterranean Episode was over. (pp. 183-184)
I'm kind of surprised he does not mention the Crusades, which seems to confirm the hypothesis--Europe was undergoing a huge youth population bulge at the time during the High Middle Ages, all of the lands that could be settled were settled, and it's generally accepted historical fact that the ambitions of younger prices, who did not inherit the lands as their older brothers did, was a driving force in answering the Pope's call to conquer the lands of the "infidels."

The next chapter presents an interesting hypothesis. It has long been known that periodic waves of nomadic horsemen have overrun settled civilizations since ancient times. The settled agricultural civilizations of the ancient Near East, those of Ancient Greece, the empires of China, and the Islamic empires have all faced down these waves. It is a major factor in world history.
We know most about the attacks which were most recent, about those of the Mongols and their Genghis Khan and his successors between six and seven hundred years ago... But we have evidence for the intermittent eruption of nomad armies from the steppes for as far back as our written records show...The afflictions seemed to come in waves, there being a few generations when the soldiers of civilized states had to fight again and again for the existence of their countries against armies of people who appeared from regions beyond the knowledge of their geography
A century or two of repose would follow, when the wounded civilizations could rebuild their shattered confidence and shattered frontiers, or win back the border territories which the horsemen had entirely taken from them...To Europeans the main floods of the last three thousand years have been associated with the names of Scythians, Sarmatians, Huns, Magyars and Mongols, though there were many other tribes and races involved in the mass movements...  
The sense of even more striking when the history of assaults on China and India is compared with it. They too were struck by Mongols, Huns and the rest, and at the same time. The great lozenge of land which is the Eurasian steppe stretches all the way from China to Europe, having a frontier with each great center of civilization in turn. It is a single geographic feature; as it were, a giant piece of real estate jointly owned by an assembly of nomadic tribes...Yet the cyclic ebb and flow of armies coming out of the steppes is apparently real, requiring an explanation. (pp. 186-189)
Some have argued that these waves of conquest were due to climatic fluctuations - warmer and wetter years on the steppe led to expansion and the establishment of empires. Colinvaux rejects this answer. Yet his explanation does involve climate--in a way.

Colinvaux argues that these periodic waves are due to a breeding strategy on the part of the steppe nomads. When years were good, people adjusted their breeding strategy and had more children. When the climate of the steppe turned sour and times got tough, these warlike people, accustomed to techniques of fighting among themselves and able to live off the land effectively, took to their horses to seek out new lands to conquer.

Colinvaux sees the perfect analogy for this periodic overrunning of settled civilizations in the breeding habits of one particular animal - the arctic rodent known as the lemming, which goes through periodic bursts of population and then fades away until the next population explosion:
Nomads of the Asian steppes lived under conditions and in ways which give a distant echo of the lemmings. They were adapted to life where there were no trees and where there was a long hard winter. They were dependent on their animals for food, transport, clothing, and even for the covering of their houses. They managed quick crops of grain when the rains came. They learned to wander far with the changing seasons, to distant pastures, to water holes. In their wanderings they were able to live off their animals, which were a moving commissariat and larder, and on grain, carried in sacks and saddle bags... 
Yet the nomad niche on the steppes was one that could not support dense populations. They ate meat and a little corn, both depending on the poor productivity of the steppes for forage and grain. Niche-spaces must usually have been at a premium on the steppes. So we have a chronic shortage of niche-spaces and an abundant supply of young adults to compete for them; few jobs and many applicants, the nomad cultures must have ways of allotting niche-spaces to some and denying them to others... 
But the fortunes of such people were critically dependent on the weather, particularly on the amount and timing of the seasonal rains. There are wet years and dry years on the steppes, as the weather changes with that characteristic unpredictability which we all know so well...Because the rains were fickle, however, the niche that the people of the steppes had learned must be adapted to cope with bad years and good. ..and all the tribes would be over huge areas at once, and all the tribes would be affected equally; they would all wander less in a good year, more in a bad...The breeding strategy of these nomad people would reflect, in detail, this niche of nomad living. Each couple would raise the optimum number of children that they could carry with them and nurture through the lean season. This optimum would certainly be a large number. The nomad niche held none of the restraints that make the wealthy of civilized states opt for small families, nor did nomads feel the privations of poor agricultural peasants or people in city slums who cannot afford to raise many children... 
All that is needed to produce a surplus of nomads across all the steppes at the same time is for some run of seasons to encourage societies everywhere to let in a few more adults, because these extra couples would each rear a new family. Perhaps a chance run of good years would do this simply by letting the people wander  less so that friction between distant tribes was less, or it could be simply that the herds grew, the mares gave more milk, and the grain sacks were filled. But any small change in habit that let the average recruitment to the tribe at puberty be slightly more generous, would ensure that the steppe would be crowded in the years ahead—especially if the new laxer habits were not easily abandoned... 
In this way the whole steppe would start filling with too many people, synchronously, because habit was triggered by weather just as the tundra of large areas can fill with lemmings. People grow and reproduce more slowly than lemmings, and the chances of weather that affect them take longer to work themselves out. That a nomad high should happen only every five hundred years or so by these means seems reasonable. 
Population highs of nomads must now be translated into armies of aggression, which is easy. Nomadic people fight over pastures and water holes anyway; more nomads on the move means more fighting in bad years; more fighting means better attention to weapons and generals; and this means the chance of raising a real army.  (pp. 197-200)
Population cycles of steppe-people as well as of lemmings are thus synchronized by weather, although they are definitely not caused by cycles in climate. Both lemmings and people use weather as cues for behavior, the lemmings for simple sex, the people more subtly. All people behave to suit the weather but pastoral nomads are more closely tied to weather than the rest of us so that small changes in habit bring large consequences in population.  
Yet the climatic pattern of good years and bad is purely random, for both people and lemmings. The length of time between one population high and the next is, for both species, set by how fast each can breed, how long each lives, and how prompt each is to respond to changes in the weather. Lemmings can raise a baby in six weeks, live a year, and produce huge populations at roughly four-year intervals. People take twenty years to raise a baby, live sixty years, and produce largish populations roughly every five hundred years. The cycles are thus properties of the animals, not of climate.  
When there are too many lemmings on the tundra, the surplus must die, or fail to breed, so that the excess crop is removed. The same is true for nomads. Surplus nomads are spent as they follow their great captain in his armies to pitch their tents in border lands once held by civilized states. The steppes are relieved of their surplus people and nomadism there may revert to its traditional ways...Fighting is no longer so necessary to the stay-at homes and the martial needs of the people which made them submit to the triumphant discipline of their generals can be relaxed. This explains the ebb tide of nomad conquests...In this way does the ecological hypothesis provide a rational explanation for the periodic wars of conquest undertaken by nomadic peoples... (pp. 202-203)
The nomad armies were never beaten. In the end they merely faded away. Like the decline of more conventional empires, this has often been seen by moralists as the result of a loss of spiritual purpose in the descendants of the conquerors. They grow soft, take to loose living, wallow in their harems, and forget that the martial graces are supposed to be superior. But such moralizing is not necessary to explain the ebb of the Mongol aggressions. The need, which had caused the people to throw up that dreadful army, had been satisfied. The wars had first diverted the frustrations of a rather crowded people with adventure and plunder, and then had removed the cause of those frustrations entirely by effecting an armed emigration. (p.210)
Colinvaux includes a chapter commenting on the American Revolution. His description of differing concepts of "freedom" - those of settled, crowded civilizations, and those of a wide open frontier are worth considering:
That England was an island state, densely populated, but with both numbers and opportunities for life expanding. The English had turned their island into a productive garden, with little wildness left. Agriculture, industry and commerce were each collecting into large scale enterprises. It was a society in which the younger sons of the better-off were already taking to trade and foreign adventure, achieving broad niches by the use of other people's lands. And the people had fashioned lies of law and government suited to their tightly organized garden of an island.  
The niches in which these English people lived reflected the organization of their developed state. The English who stayed at home expected their futures to be narrowly circumscribed. There was a place for each in society, but little choice of place. It was a society of castes, liberal by the standards of many a caste system, but a society of master and man nevertheless.  
Yet the English were thriving on the new developments in agriculture and industry. The optimum family size was large for all classes  and the population tended to grow rapidly. This rise in the numbers of the English is well documented. The English themselves knew what was happening, and they were alarmed lest their prosperity might be undermined thereby. Contemporary writers set down the dilemma and one of them, Richard Eburne, showed that salvation was to be found in the mass export of people to colonies.  
The English in America brought with them that English concept of freedom under the law, complete with deference to authority and restrictions on behavior appropriate to life in a full-up island laid out like a garden. American elders read of the island life, some were homesick for it, and others learned about it from the regular flow of immigrants who brought it with them. But the way of life, the niche, found to be so satisfactory for England was not so appropriate to Englishmen in America. Why accept the social system which had been found necessary for a well-peopled garden? Here there was room for everyone to do as they pleased, respecting their neighbor perhaps, but not neatly fitted into a neighbor's affairs as the English in England were. Why be master and man when there was room for everybody to be master? A new form of liberty was possible in which each could pursue happiness with much less deference to vested interest. Gradually the niche of an American took shape, described though it was in the language of England.  
Niche faced niche across the British muskets in Boston; a niche suited for a crowded island and a niche suited to the almost unlimited possibilities of a new continent. Both peoples used the words "freedom" and "liberty" when they described their purpose, and, hence, the niches they were to preserve. But the British talked of the regulated freedom of a complex society wherein choice was necessarily limited by the numbers of other people needing their shares, and the Americans talked of the much wider freedom possible when opportunity and resource were virtually unlimited. (pp. 219-223)
Indeed, we see this in the rallying cry of "freedom" in the United States - the freedom to consume as much as we want and to do as we please, everyone else be damned. It's worth noting that America's period of imperial colonial expansion--the Spanish-American War--occurred almost immediately after the frontier was declared "closed" and "settled." And when that was no longer possible, we entered the technological "frontier" - the vast expansion of niche space through the development of technological marvels such as electricity and the internal combustion engine. Frederick Jackson Turner's "Frontier Thesis" is an elucidation of these ideas.

After World War Two, America alone was the global superpower, able to divert a quarter of the world's resources to itself while the rest of the industrial powers were reduced to rubble. As Morris Berman points out, Americans have always had some sort of frontier and are conditioned to rising living standards in perpetuity, unlike other cultures. This gives a great insight into the American character.

Americans are now freaking out because rising numbers mean that we can no longer do as we please. As numbers rise, new bureaucracy crops up to deal with rising numbers. Social mobility--long considered a birthright--stagnates and degenerates into a rigid caste system (enforced today by the university-educational complex). Americans are living in smaller houses, turning down the thermostats, driving smaller cars, and tightening their belts, all while being told that their wastefully obscene living standards are unsustainable, as indeed they are. This is leading to recrimination and blame, as numerous conspiracy theories such as "Agenda 21" can attest. It is not conspiracy, but the fact of rising numbers, and other nations finally being able to contest for those resources.

Now, frustrated American are aghast at the possibility that may have to live like "Europeans," in apartment blocks without acre-size lawns and riding lawnmowers (i.e. like the rest of the world). They occupy government buildings to protest "tyranny" of having to pay grazing fees to use public land. They stockpile guns and ammunition to defend their "freedom." and use them to menace government officials who come to install energy-efficient smart meters. They balk diverting funds to public transportation rather than expansive freeways for private automobiles, denouncing this as "socialism." They belch coal smoke from their oversized vehicles to protest the adoption of energy efficiency measures and solar power. Politicians constantly rail against taxes and regulations that people of other nations simply see as their civic duty, while fulminating about "freedom" and "liberty."

Is it any wonder that it is primarily Americans who are are devoted to the idea of someone coming up with a solution to all of the world's problems via some sort of technology developed "in their garage," or with getting off "this rock" and colonizing Mars and outer space?

If there is a major flaw in this portion of the book, it is his focus on Western civilizations to the detriment of Eastern cultures, especially China. This most likely is because the book was published in 1980, coincidentally around the same time as the beginning of China's rise to world power status. Because of this, much less was commonly known about China's ancient history by Westerners and there was less scholarship on this point, which is probably why Colinvaux does not devote much discussion to it.

Which is too bad, because China's history is an even greater confirmation of his ecological hypothesis. China has always acutely felt the weight of rising numbers and crowding--indeed I would argue that this is the central pivotal fact of Chinese history. China would consistently bump against a civilizational plateau due to increasing numbers, and would collapse down to a lower level. Unlike the West, they were unable to break through this plateau through technology or colonization; indeed China was famously insular and solipsistic. This led to caste systems and cultural stagnation, as Colinvaux describes. In fact, Ancient Chinese historians were among the first to describe their history in terms of repeating cycles in books such as the Shujing, or "Classic of History."; describing what they called the "Dynastic Cycle."

China's rise since 1980 has seen the ecological hypothesis playing out in a nutshell: rising numbers, rapid growth and industrialization creating new wealth and new niches, repressive government, abandonment of the countryside and flight to the cities even as numbers increase (slower in China due to the one-child policy), concentration of wealth, and now, potentially, imperial expansion and diaspora. That fact that China has tracked the ecological hypothesis so closely since the book was written--something Colinvaux could not have foreseen in 1980--is an impressive confirmation of the book's central thesis.

Another important omission is the impact of rising numbers on ecological degradation and the use of fossil fuels and technology for growth, which has been a central fact in world history since at least the nineteenth century. This is odd, especially in a book purporting to use ecology to explain the historical process (the passage above about Athens is an exception). In his concluding chapter, however, Colinvaux does address some of these issues.

 In his concluding chapter, Colinvaux meditates on the ramifications for the future:

The human breeding strategy remains what it has always been. Each breeding pair acts to maximize fitness, which we define as the number of offspring who survive them to breed in the next generation. Fitness in human breeding is largest when the chosen family is at an optimum, not too large and not too small. But this optimum number is very sensitive to the broadness of the niche to which the children are to be raised.
The relatively poor will always have larger families than the relatively rich. The experience of history is that the average family that results is more than is needed to replace the parents, even among the affluent. The only circumstance in which families fall below replacement is in the more extreme forms of poverty, where resources are so constrained that the optimum number falls to below two.
Populations tend to rise most quickly following a large increase in resources or standards of living brought on by a major technical advance or a successful aggression. This is because the optimum family then can be seen to be large by people of most standards of affluence, but particularly by those being recruited from the poor to the middle classes. The spurt in numbers always ends when the new resources, won by technique or conquest. are used up; after which the population continues to increase, but more slowly. Many modern nations have just passed through, or are still in, one of these periods of rapidly increasing numbers.
There is an important variant on the effect of fresh resources on the optimum family. It is that hope, alone and by itself, will raise the number of children chosen. Any reason for rising hope in a population always leads, therefore, to rising numbers...hope itself will lead to larger families. This is inherent in our breeding strategy...A feeling of well-being makes the numbers rise.
Rising numbers must always soak up spare resources by sharing them out among the extra people. One consequence of this is that poverty always persists. A second consequence is that good times for the not-so-poor must always end in some successor generation producing a predictable series of events which include trade, colonialism, class repression and aggressive war. Since our own numbers will continue to grow, it is inevitable that our own future holds variants on these themes. (pp. 318-319)
As noted earlier, Colinvaux dismisses the idea of the "demographic transition." This point is critical, because the idea that charging full steam ahead with massive industrialization in order to bring the developing world up to exorbitant Western living standards is seen as the silver bullet to the overpopulation crisis by the so-called "Bright Green" or "Ecomodernist" movements. This idea is heavily promoted by those who have a stake in promoting "pro-growth" policies, such as governments, bankers, businessmen, corporations, and wealthy elites (The Davos crowd). See, they argue, growth solves it's own problems!!

Colinvaux would surely regard such people as utterly delusional. Rising living standards cause people to have more children, not less, as noted above. Wealthier couples may have less children on average, but it does not mean that populations will stop growing altogether. Since wealthier people consume more anyway, increasing wealth to stop population growth seems like a self-defeating strategy if you want to deal with resource use or carbon emissions.

It is true that a number of wealthy countries are experiencing stagnant, or even falling population growth rates. It is possible that the root cause of this is the pinched living standards of the younger generations caused by crowding, extreme income inequality, and increased economic competition due to globalism. Europeans, for example, would consider the conditions under which many children and adults live in places like Sub-Saharan Africa or Latin America as unacceptable (this is less true of America, hence it's higher growth rates). This is leading them to delay, or even forego, staring families at all, because children are seen as simply "unaffordable" for younger couples. A tradeoff is perceived between having children and maintaining an affluent Western standard of living, with its self-actualization opportunities, leisure time, and consumption patterns. Social and religious taboos against not getting married or having children have also been relaxed.

This was not the case in the past, where Europeans were either poorer or richer on average. There seems to be a strange national "middle-income trap," where most people are rich enough to care about their children's prospects, but not rich enough to guarantee both themselves and their children a bright future anymore without painful sacrifices. Western societies tend to make children an economic burden, rather than a necessity, which they are seen as in places where the family structure is still intact, work is more informal, and there is no social safety net nor old-age pensions. Subsidies to parents promoted by political elites are having little effect, because the subsidies cannot offset the costly educational burdens for the few jobs which pay decent wages, nor the soaring housing costs and stagnant incomes. All of these are consequences of crowding, and cannot be solved merely by government meddling.

It is also thought that by empowering female education and mating choice, birthrates will drop as well. There is some truth to this, but it is often accompanied by Western cultural imperialism and a destruction of traditional lifeways which have sustained people for countless generations. These are replaced by Western-style "free markets," where everyone is suddenly placed into competition with everyone else in a "sink-or-swim" type environment. It makes no sense to educate women if they simply displace men from the workforce causing mass unemployment, which is what we've seen so far under corporate globalism. As Colinvaux pointed out earlier, there need to be enough niches for the newly educated people, otherwise there will just be more conflict, not less, as there are too many claimants for the available niches. Thus increased education, including of women, before economic development, can actually be destructive. Educating women has often been accompanied by a loss of wealth and prestige for men, leading to extreme reactionary movements, the most extreme of which are the Islamic State, the Taliban, and Boko Haram, all of whom are not coincidentally opposed opposed to Western education (Boko Haram even translates as roughly this).

It's also worth noting that areas outside the affluent West are still growing very rapidly, and the crush of people is sending a tidal wave of refugees, both political and economic, to the wealthy, Western countries. These people all want to live in the broad niches that Westerners currently occupy, with the conditions noted above. Immigrants are being brought in to fill the undesirable narrow niches of Western societies. With their traditional social structures, and unaccustomed to Western wealth and comfort, their breeding strategy is to have as many children as possible, displacing the native population and causing social conflict. The migration crisis is utterly predicable from the ecological hypothesis, although Colinvaux fails to predict it using his own theory.
The assertion that spreading wealth will halt the growing populations is a statement of what is called in the textbooks the "theory of the demographic transition."...The idea does not have the status of a formal theory, in spite of the name given to it. It is merely the observation, now commonly made and well established, that more-affluent people have smaller families than poorer people. This is explained by niche theory, which truly is a theory and which explains the observation. There is  no evidence that making people wealthy will halt population growth, merely that growth will be somewhat slower when we are all wealthy.
The way in which the demographic transition argument is often offered makes it particularly dangerous to the human well-being. In its most glib form it slides out as a sentence something like this, "We now know that poverty is a cause of population growth and not a consequence." The implication is that, if we will only get down to producing wealth and sharing it with the poor, history will go away. But that glib sentence is utterly false. It is based on nothing other than the belief that there is some magic in being wealthy that sets the family  at replacement. A rising population is the cause of increased poverty; niche theory predicts that it will be so; the historical record shows that it always has been so. (p. 320)
He also dismisses medical advances as automatically putting a halt to population growth:
For a few years when first introduced, medical improvements probably do cause a few more children to be raised in a single generation, because, as I have said earlier, the families of that generation will have been conceived in ignorance of the effects of the new medicine. The effect has no long-term significance, except to let people plan their optimum family with greater precision. But to assume that the recent invention of mass medicine has made any fundamental difference to the number of children raised in any contemporary society is to assign to people the small-egg gambit of a mosquito; it is to assume that women are mere baby factories and their output is a function of what the doctors can keep alive. It is unscientific as well as literally inhuman.(pp. 321-322)
And finally, there is the idea that there is some sort of magic "inflection point" in human numbers,  just as there is with mice or bacteria, which will come about naturally and without much pain. According to Colinvaux, this is to misunderstand history and the breeding strategy of large animals such as humans:
This leaves the third assertion which can best be described as "the doctrine of inflection in the growth curve." The argument goes like this: the rate of growth of the human population is not so steep as it was before; therefore, we may say that it is starting to "level off  and this looks like "the point of inflection" on the growth curve of small animals in a laboratory experiment. 
When you put healthy fruit flies, or flour beetles, or mice, or flesh flies, in a suitable laboratory cage and give them all the food, water, or bedding they need, they engage in healthy reproduction. The numbers in the cage begin to grow...You put in fresh food and water daily, more than enough for their needs, making every effort to keep them comfortable. The population begins to grow more and more rapidly, geometrically, exponentially, faster and faster and faster. The growth curve by now looks like one of those horror charts of projected growth of the human population from sensational "ecology" literature. And then the rate curve levels off; there is indeed a point of inflection when the population ceases to grow...It is to this history that we are invited to compare the recent progress of the human population.
The laboratory populations "inflect" because their cages become so crowded that the animals have to struggle for food; or because they no longer have space for some of the vital activities of their niches; or because they blunder into each other and bite by mistake; or because they eat each other's eggs. These troubles interfere with the breeding efforts of the animals...The birth rates go own because of privation, and the death rates go up through similar privation. Is this what is happening to the human population? When the population growth of mice in a cage finally stops, one of the things that happens is that mothers eat their babies, definitely making the population "inflect." The absurdity of comparing human history with this is obvious.
Many wild populations of animals, particularly the big ones to which we relate most easily, seem to be constant from year to year, showing that some ancient growth curve must have leveled off in circumstances less drastic than those we engineer in a laboratory cage...The very last individual for whom there is room is supported and no more individuals can be recruited to the population. Extra individuals are always being produced but the surplus are denied a chance to live. This is the only scientific explanation of this kind of population stability that has been found. Competition or predation removes surplus individuals when all the living[sic] has been taken up by others. Any other explanation invokes magic. (pp.322-323)
Given that so much of the book is devoted to military history, it is not surprising that Colinvaux takes a look at the future prospects for war. Since that the book was released at the height of the Cold War, Colinvaux contemplates a possible nuclear exchange between the U.S. and Soviet Union, and considers scenarios where this would be strategically make sense (which thankfully did not happen). But he does describe the circumstances in which he believes future wars are likely to occur:
The first requirement of aggression is a rising standard of living. Niches of the ruling classes of the aggressive population have been getting broader, requiring more and more resources for each person. The ruling class will have worked to spread the new standards to poorer sections of the community and there will have been a history of partial success for this effort. More and more of the people will have been living better...
A high standard of living always includes more chance to choose a path in life and is, therefore, seen as a form of freedom. Aggressive armies fight for loot to support a standard of living, but their spokesmen talk of fighting in the cause of liberty...The belief that you are fighting for liberty is a second general requirement for a war of aggression.
A rising population is a third requirement. This condition will automatically be met when the standard of living is improving and there is a sense of greater freedom...
A fourth requirement is that much effort has already gone into meeting the needs of the new freedoms by means less costly than aggressive war...The potential aggressor...will have made good progress at expanding its resources by technique in agriculture, industry and government. It will have a strong merchant class...And it will have communities of its own people dependent on providing or consuming the goods of trade for their regular employment. In material things, therefore, the aggressor state must already be comparatively wealthy.
The fifth requirement, and an extremely important one, is that there must be a suitable victim. The ideal victim is a society that is technologically backward by the standards of the aggressor. It will thus have land and resources from which the aggressors know that they can extract a higher standard of living, possibly for more people than the victim did...
All aggressions are attempted from positions of apparent military superiority. This sixth requirement means that the aggressor usually has, not just a large army, but soldiers with superior technique...And in all successful aggressions with lasting results, this requirement has in fact meant that the attacking army has weapons or tactics which are clearly superior to those of the victim and which the victim cannot copy...There have been many aggressions in which the apparent military superiority of the attacker turned out to be illusory...Aggression never comes from a poor country against a rich country, except in very special circumstances. It can happen that a nation appears poor by some standards of measurement, but is wealthy by the test of its own history...
It should be obvious that very many of the nations of the contemporary world are growing in ways that must soon let them fit this profile of a potential aggressor. Standards of life, hopes for liberty, and numbers of the people are all rising together. Many nations show a strong interest in military affairs. Whether they will actually go to war will depend on their finding suitable victims. (pp. 324-328)
One is forced to consider the ramifications for China, a country which has experienced a generation of rising living standards and is now reaching the limits of providing new niches through economic growth and trade. China has the world's largest army, the world's second largest economy, has been making military threats over islands in the Pacific and building carrier fleets, and is experiencing an economic slowdown. India, soon to surpass China in population, has had numerous conflicts with Pakistan, and both are nuclear powers.

While this is fundamentally sound, I question a few of the conclusions. it is hard to see what the United States gained from many of its aggressions, such as the Vietnam War of the Gulf Wars. The Gulf Wars can at least be seen as a means to stabilize trade routes and secure the price of the oil resource.

Which is a good segue into something I think Colinvaux missed: trade is the new war. A society can now be looted simply by means of the economics of banking and debt, as Michael Hudson has repeatedly pointed out and described in great detail. Wars are expensive and costly, and with the deadliness of modern weapons, it is very hard to conquer and hold territory anymore even for the most powerful nations. Much of the "aggression" by the West has been through economic means against places like Iran, Argentina, Mexico, Greece and Venezuela, rather than outright war.

As Westerners left the colonies behind, they erected an economic system which ensured that the vast resources of the so-called Third World would continue to flow to them. The impoverished regions of Africa, Southeast Asia, Latin America and the Caribbean continue to provide the goods and raw materials which flow to the West and sustain our present lifestyles. The Amazon rainforest is chopped down for American beef; Indonesian forests are burned down to produce palm oil plantations for Europe; Thai mangroves are destroyed to make shrimp farms, Latin American farmers produce our coffee and chocolate, and African children mine the rare earth elements needed for our smartphones and wind turbines, all out of sight. War is no longer required. Political corruption and repression in these societies keeps these "banana republics" in line, and if some "socialist" leader even thinks of tipping the apple cart and using some of the resources for his own people, he is swiftly targeted with economic sanctions, followed by clandestine assassination/coup attempts, and finally a carpet of bombs dropped by Western air forces.

This use of economic warfare is missed by Colinvaux, probably because 1980, in addition to being the start of China's rise, was also the beginning of Neoliberalism's (aka free market looting) rise to become  the dominant economic ideology of the West. It, too, can be seen as a way for elites to open new opportunities (liberalized global trade and buying up common-pool resources via the Shock Doctrine) and maintaining their extravagant lifestyles which were under pressure from below, as the crises of the Seventies showed. It certainly has worked: a handful of people who could fit into a medium size conference room now control as much wealth as half of the world's population.

Colinvaux discusses the "three great technologically prosperous empires:" The United States, Europe, and the (former) Soviet Union. He also focuses on mercantile island nations such as England and Japan. This causes some of Colinvaux's predictions to go awry. I've already noted he missed the rise of China (which follows from his own theories). The salient point about the Soviet Union was not war, but collapse and breakup. This, too, follows from the ecological hypothesis: it's likely that there was no way to accommodate the rising aspirations of the middle classes within the old, sclerotic Soviet bureaucracy. Political repression can only go so far, and the enticements of broader niches made available by access to the West was enough to tip the balance. For Japan, the salient point has been economic stagnation and falling population.

As for Europe and the U.S., while there have been resource wars (Iraq, Afghanistan), and economic warfare (Venezuela, Iran), I would say the main points have been the stagnation of living standards, the dismantling of the state (austerity), extreme inequality, and especially the impact of mass immigration--from Latin America to the United States, and from the Middle East and North Africa to Europe. These have reached such levels as to become politically hot-button topics for power-hungry demagogues. As I mentioned before, mass migration is predictable from the ecological hypothesis. Colinvaux also misses the complete collapse of the Middle East, which has combined repressive regimes, a youth bulge, mass unemployment, radical ideology, acute resource shortages such as fresh water, and rising food prices together in a witches brew of state failure and social collapse.

As for energy and resources, Colinvaux points out that the lifestyles of the affluent West are entirely dependent upon cheap and abundant sources of energy. Again, this is presented as sort of an afterthought, which is too bad, because this is the major reason why arguments like Colinvaux's are dismissed out of hand. This is why I wish he would have dealt with this topic sooner and at more length than in the book's concluding chapter:
The well-being of the European West was built on cheap energy. All previous civilizations used energy that was expensive, human labor supplemented with a little work from animals. Energy is the power to do work. It is necessary to most of the dimensions of a broad, civilized niche.
It was failure to find a source of cheap energy that led to economic stagnation in the later days of the Roman Empire. Romans relied on slaves to make things, carry things, and to do for people of cultivated ways those services that make cultivated living possible. This made certain that very many of the people, the slave classes, would always be poor, but an even more serious consequence was that the very high cost of energy meant that businesses could not get ahead; they could not easily make large surpluses; they failed to generate capital. And a poor business income meant a low tax base, a government short of funds, stagnation in the armies, and eventual collapse. Any civilization poor in energy cannot meet the costs of elaborate government and supply needed by crowding numbers.
Even before the industrial revolution, the European West began with a technology base which was better than that of any previous civilization. Then it found the Americas to take its surplus people and let the numbers grow without impossible strains on the costs of government. And then, after two centuries of growth and conquest without a fossil-fuel economy, it found how to use coal and oil to do the work that had been done in other civilizations by slaves. The coal and oil lay on the ground, loot to be had for the cost of picking it up. It was this loot of fossil energy that let the West come within measurable distance of abolishing poverty, despite their rapidly rising numbers. They could generate capital, give opportunities for trade to more people. carry people in and out of cities to use resources of space in turn, build them houses, free them from brute labor and give them time to experiment with their powers to learn. A very large portion of the people have become wealthy in the sense that they have had the pressures of rapidly risings numbers tending to maintain a subculture of poverty in even the wealthiest cities, but energy has been so cheap that new ways of living could be invented, for a time, as fast as people were bred to fill the new niche-spaces. Yet it all has depended on a very large flux of very cheap energy. (pp. 332-333)
As I mentioned earlier, sophisticated technology, applied science, and extravagant energy use have been the major economic factors for the past one-hundred and fifty years. These have led to increased living standards alongside population growth, although it can be argued that the former caused the latter and not the other way around.

This have caused most people to argue that rising populations are no longer a problem, nor will they ever be again, and that we have left the Malthusian world behind once and for all. We will always have science at our disposal to increase our productivity in perpetuity to stay ahead of population  growth. There is no limit to what the earth can provide, and the pressure of rising numbers will always bring forth sufficient "innovation" to solve any problem as it arises. This is taken as an article of almost religious faith by the West.

 Again, Colinvaux would regard such people as delusional at best, mendacious at worst. How does the above idea square with the fact that we are already being told we are going to have to eat less meat to save the planet (eerily echoing the loss of meat consumption faced by our earliest agricultural ancestors). Insects are now being touted as the only way to provide sufficient protein for growing numbers. Wild-caught fish are becoming a delicacy due to declining fish catches, with farm-raised fish lower in vital nutrient as the affordable alternative. Even people in rich Western societies are being treated to horsemeat, and beef is replaced by "pink slime" and "meat glue." Is this the innovation that the boosters are touting as "progress?"
We see the effect of crowding everywhere we turn. The younger generation has embraced the "tiny house" movement, and  even the smallest apartments are unaffordable in big cities such as New York, London and San Francisco, where prices are out of control. The quality of even large houses is terrible, comprised of the same glued-together particle board that makes up our shoddy furniture. Metal has been replaced by plastic, disposable goods quickly fall apart, and our thin fabrics wear holes in them after a few months of wear. Energy efficiency is a good thing, but lets not pretend it is some great product of "innovation" rather than a way to maintain our exorbitant lifestyles in the face of rising numbers and declining resources.

Increased competition due to a lack of niches is causing longer work hours along with a burgeoning prison/guard labor industry to deal with the fallout. The elderly are compelled to work and the youth are being denied entry in the job market. Expensive university education is not a bug, but a feature designed to ensure only children of the affluent will inherit the more desirable niches. Social mobility is long gone, and a caste system has descended. Nepotism is rampant. A repressive police state beyond imagining has been constructed in nearly every Western society in the span of a decade. Even life expectancy is decreasing for some demographics for the first time in over a century.

All caused by the weight rising numbers. How can we really continue to argue that we have left the Malthusian world behind forever? We only took a break thanks to one-time breakthroughs that cannot be repeated, as Robert Gordon has recently pointed out (but does not go far enough).

It's not just cheap energy, but also cheap food, that has allowed for the vast population growth we've seen over the past two hundred years. The two are related, of course. Here it is worth quoting Colinvaux at length:

The rise of the west also dependent on cheap food. At first the cheapness came from the new agriculture of novel crops and crop rotations, the farming from which the cities of Renaissance Europe and Tudor England were fed. Then came the vast glut of cheap food from America, that glut which forced the English government to repeal the corn laws and destroy its own farming industry. The English countryside became depopulated despite the massive growth of the British population. Even in America itself a similar thing happened as large areas of New England, once farmed, were given back to the wilderness in the face of competition from prairie wheat and corn. A historian of the future looking at the record of either old or new England from this period could make the same error of historians of the later Roman Empire who imagine that the population was falling.
The next cause of cheapness in food came from applying the new cheap energy to agriculture. Tractors, harvesting and planting machines and, above all, chemical fertilizers lowered the costs of growing food even as they increased the total supply. The cheapness of food from this episode, now ending, was entirely dependent on the cheapness of the very large fluxes of energy used.
There then came yet one further push to cheap food. This was the development of crops such as hybrid corn, a new agriculture that goes by the name of the "green revolution" in the contemporary press. This agriculture is completely and inextricably dependent on a large flux of cheap energy. The ecological engineering that went into making the new varieties is elegant, but the plants are made to rely on our supplies of cheap energy in order to grow at all. An understanding of this dependence of crops on fuel energy is vital to understanding our future.
The total energy that all our crops can trap from the sun is set in ways that we have not been able to alter. Most likely the actual limit is set by access of the plant to carbon in the air, for it cannot make sugar faster than it can get carbon. All crops and wild plants accept this limit alike, and we have not been able to increase this primary production of plants by one iota. What farmers have done is to breed varieties of plant that put down more of their store of sugar into parts that people like to eat. We measure the productivity of a wheat crop by the weight of grain, not the weight of roots, stems and leaves. Cultivated wheat puts much of its energy reserve of sugar into grain whereas its wild ancestor used most of the reserve to maintain healthy roots and stems in the rough and tumble of wild life, but both kinds of wheat had the same sugar to start with.
With the new varieties of the green revolution we have pushed this process one step further. We have taken over many of the functions that a wild plant had to do for itself, and have done it for the plant ourselves, in factories. We do not let the plant hunt out scarce minerals with its roots, we give it superabundant supplies of fertilizer so that it does not have to work for its nutrients. We take away a plant's ability to protect itself against disease and pests, because the plant used to spend part of the energy reserves of its grain to do the job itself. Instead we protect the plant with chemicals. In other words we keep alive, with fertilizer and chemicals, a plant that would have had no chance of hacking it alone, and the energy that its ancestor would have spent in fighting its own battles is then freed for the plant to make more grain, this extra grain, therefore, is entirely dependent on the cheap fuels supplied to our chemical industries; indeed, in a real sense the energy of this extra grain is some of the energy from the chemical industry. We are actually eating fossil fuel. And this fuel is soon going to be expensive almost beyond our present understanding. (pp. 333-335)
As for the future of cheap energy:
Western society has been built on the treasure hoard of fossil fuel lying loose at the surface of the earth. It is as if we have been living on the loot of some vast and undetected robbery. But the loot is far gone. The oil may be half used, or more. There is still coal, but the  best, or at least the most easily reached, is gone. We have bred very large populations to use this cheap fuel so that our use is now at a rate which means that the remainder must be spent far more quickly than what we have used already. And now the rest of the world wants to use fuel as we have done. We must share the swag--what there is left of it.
This means that energy will soon be expensive whereas once it was cheap. It is not that we will run out of energy; it is rather that we will run out of cheap energy. Indeed, we already have, though present (1980) prices are still absurdly low by the standards of what will be the norms ten years from now. Oil, and then coal, will soon be so expensive that nuclear reactors will seem economical to run. We can then pursue research into whatever esoteric methods of energy production we like. There will always be energy, but at a very high price. Never again win energy be cheap, plentiful and easy to extract. This is a fact with profound implications for the politics of nations.
Cheap food too has gone forever. The good parts of the earth are all farmed, and the yield does not quite keep up with the demands of the increasing numbers of people, the crops of the green revolution will be extremely expensive to produce as energy prices rise, probably, in fact, too expensive for poorer countries to use them at all. To the extent that these new crops are abandoned, food production will actually fall, requiring that prices go up in response to the increasing imbalance of demand and supply. Demand too will grow as our numbers continue to grow. In the productive agriculture of the West, farmers will have to start economizing in the use of tractors and fertilizer, as their energy costs climb. They will find themselves using more labor, both human and animal. Their yields need not fall, but the price must go up.
We are, therefore, moving into a time when both energy and food will be dear. Many patterns of civilized life are about to change as a result. The spreads of cities will be different, the countryside will be repopulated, there will be quite different patterns of work and play. It may not be something to fear; it may be rather an opportunity, like all change, for the most adventurous to welcome. Perhaps we can dismantle city governments, break monopolies of power, live country lives when we want to, and work in small industries for brave entrepreneurs instead of serving some giant corporation. Change is always good for the brighter spirits, and the high cost of fuel and food make drastic change inevitable. But the new patterns must certainly offer new temptations and straits which might drive nations to battle, even nuclear battle.(pp. 336-337)
Pretty impressive considering it was published about twenty years earlier than books such as The Party's Over, Hubbert's Peak, and The Long Emergency.

And we've earlier seen how rising numbers inevitably bring about more bureaucracy, more laws, more regulations, and less freedom. This is not some "conspiracy" of elites as certain more paranoid quarters like to argue, nor is it a nefarious scheme of socialist bureaucrats simply to feather their own nests as libertarians argue. Rather, it is a logical and inevitable consequence of rising numbers:
There must now be fear that the press of restriction will increase, possibly rapidly, because we are about to lose our large flux of cheap energy and cheap food. Almost inescapably, lack of cheap energy will mean lack of cheap capital, which will lead to a progressive shortage of new opportunities for living well. Since the numbers of people must be expected to continue slowly to rise, then the progressive loss of freedom that we already experience must accelerate. (p. 348)
In Europe the mass of the people have long been denied the use of wilderness or countryside by patterns of "ownership" that make "no trespassing" a common sign of law. Americans are still happily ignorant of laws against tresspass, yet they find fewer and fewer places where they can go without checking with some official first, Americans must reserve time to climb a mountain, file travel plans if they walk in the climb a mountain, file travel plans if they walk in the Sierras, get permission before they wander in an Alaskan wild place. We can no longer do as we please because so many people want the land that they cannot all use it at the same time. So the land is rationed—though various euphemisms are used for the offensive socialist word "ration." (p.347)
City, suburban and business fife is set about with regulations—irritating, pettifogging, bureaucratic restrictions. We blame governments for being too big and remote but, whether the mood of the electorate swings to the left or the right, nothing much seems to change. Yet it is not some error of government that causes this restriction, it is the gentle jostlings of the people. It IS a result of people-pressure. The irksome mounting of petty restrictions, which president and prime minister alike have not been able to stop, is the fruit of expansion when the numbers of people are only a little fewer than the number of opportunities there are to let them live in a reasonable way. The people must be rationed to niche-spaces, and bureaucratic restrictions are the ration cards.(p. 348)
The older societies always developed very oppressive social systems when the rising numbers could be accommodated in no other way; the mass was compressed so that the few might live well. Likewise we find ourselves beset by the big government which is part of this process...If we do not find ourselves ranked more steeply by social caste, it is because we have earlier gone so far in removing poor, narrow and low-caste lives from our society entirely...each society will find other ways of keeping people in their places. Probably this means state socialism with its idea of equal shares of what little there is, backed up by the sanction of law. Our choice, therefore, will be rationing by caste and wealth to yield unequal shares in great variety or rationing by the apparatus of a socialist state with it inevitable uniformity.
Liberty, in the Jeffersonian sense, cannot survive a continual packing-in of people. If our numbers continue to rise on a resource base that expands but little, the future inevitably holds ever greater restrictions on individual freedom. Our descendants will not be able to live as we live and our free American and European ways of doing things will seem like poems of the past. Liberty will fall progressively as the  numbers rise, and obedient compliance with the majority Will must take the place of individual initiative. Perhaps some politician cleverer than the rest will arrange this necessary peaceful compliance and call it "free." (p. 349)
Such were Colinvaux's conclusions back in 1980 based on his ecological hypothesis, and I think it's safe to say, with a few reservations noted above, that it has held up pretty well and been pretty accurate in predicting our present course in the years since it was first published. Even events which he missed could be reasonably derived from it as noted above.

Since much of these entries could be contrued as rather disconcerting and disheartening, I will end on a positive note with this sentiment from the author:
This is a good time to be living, for ours are the generations with accumulated knowledge and who yet see the end of the easy times with their swag of free energy. Change, the friend of the clever and the innovative, is close upon us. There are going to be some good and interesting things to do. (p. 351)

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