Why people read a certain book often contains more information than the book itself, and there is rich information content in the brisk sales of Jared Diamond’s Collapse: How Societies Choose to Fail or Succeed. Diamond picks out of the rubbish bin of history a few cases of nugatory interest in which environmental disaster overwhelmed a society otherwise desirous of continued existence. According to the publisher’s notice (I do not read such piffle), Diamond avers that the problem was in breeding too fast and cutting down too many trees.
The silly Vikings of Greenland refused to eat fish, disdained the hunting techniques of the Inuit, and consumed too much wood and topsoil. As a result their colony collapsed during the 15th century and they all died. One feels sorry for the Greenlanders, though not for their cousins on the Scandinavian mainland, who just then stood at the cusp of their European power.
Something similar happened to the Easter Islanders, who chopped down all their palm trees and the Mayans of Central America, who burned their forests to build temples. Diamond thinks this should serve as a warning to the inveterate consumerists of the United States, who presumably also face extinction should they fail to erect legal barriers to suburban sprawl.
Ideological reflex is too mild a word for this sort of thinking; perhaps the term “cramp” would do better. Given that America returns land to the wilderness each year, the danger to American survival from deforestation must be on par with the risks of being hit by a large asteroid. The world is not breeding too fast – birthrates are everywhere falling – and the industrial countries (except for the Anglo-Saxons) fail to reproduce at all.
Why should the peculiar circumstances that killed obscure populations in remote places make a geography professor’s book into a bestseller? Evidently the topic of mass extinction commands the attention of the reading public, although the reading public wants to look for the causes of mass extinction in all but the most obvious place, which is the mirror. Diamond’s books appeal to an educated, secular readership, that is, precisely the sort of people who have one child or none at all. If you have fewer than two children, and most of the people you know have fewer than two children, Holmesian deductive powers are not required to foresee your eventual demise.
After rejecting revealed religion, modern people seek an sense of exaltation in nature, which is to say that they revered the old natural religion. If you do not believe in God, quipped G K Chesterton, you will believe in anything. It is too fearful to contemplate one’s own mortality, so the Green projects his own presentiment of death onto the natural world. Fear for the destruction of the natural world – trees, whales, polar ice-caps, tigers, whatever – substitutes for the death-anxiety of the individual. I discussed this under the title, “It’s not the end of the world – it’s just the end of you,” and am told that Rush Limbaugh read the whole essay aloud on his radio program. 
In fact, the main reason societies fail is that they choose not to live. That is a horrifying thought to absorb, and the average reader would much rather delve into the details of obscure ecosystems of the past than reflect upon why half of Eastern Europe will die out by mid-century.
Suicide is a rare occurrence at the individual level, but a typical one at the level of nations. Even among the most stressed populations in the world, eg the Neolithic Amazon people of the Guarani, the suicide rate is small compared to the total population. According to Survival International (survival-international.org), 330 of the 30,000 Guaranis killed themselves during the past 17 years, a sad response to the shock of engagement with modern culture.
We know little of small peoples who died out in antiquity or even Medieval times, but the case histories that have come down to us are compelling, precisely because they include the most successful civilizations of the West, namely classical Greece, Rome and Byzantium. Countless small tribes disappeared into the hands of the Roman slavers, doubtless quite against their inclinations. As Robert Marcellus wrote in The Human Life Review:
The Greek geographer and historian Strabo (63 BCE-21 CE) described Greece as “a land entirely deserted; the depopulation begun since long continues. Roman soldiers camp in abandoned houses; Athens is populated by statues.” Plutarch observed that “one would no longer find in Greece 3,000 hoplites [infantrymen].” The historian Polybius (204-122 BCE) wrote: “One remarks nowadays all over Greece such a diminution in natality and in general manner such a depopulation that the towns are deserted and the fields lie fallow. Although this country has not been ravaged by wars or epidemics, the cause of the harm is evident: by avarice or cowardice the people, if they marry, will not bring up the children they ought to have. At most they bring up one or two. It is in this way that the scourge before it is noticed is rapidly developed. The remedy is in ourselves; we have but to change our morals.” 
Sparta, the model of slave-based military oligarchy, had 5,000 land-owning families at the time of the Peloponnesian War, but only 700 by the third century AD after Epiminondas broke the Spartan hold over its helot population. Rome’s population fell to perhaps 100,000 during the seventh century from 1 million in the second century. Between 150 AD and 450 AD, the population of Rome’s Western empire fell by about four-fifths. Constantinople held 250,000 people in the ninth century and between 600,000 and one million during the 12th century, yet it had fallen to only 100,000 when the Turks took it, at least in 1453. After Constantinople, the world’s largest city west of the Indus, well may have been the Aztec capital Tenochtitlan. Estimates of the annual number of humans sacrificed by the Aztecs range from 20,000 to a quarter million per year. Although Aztec civilization was overthrown by the conquering Spaniards, it could not have lasted indefinitely given such practices.
There is endless debate about such data. Roman population data are somewhat conjectural, and Strabo’s estimates have been disputed by some scholars. Explanations have been forwarded that range from the collapse of the slave-based agricultural system to mass infanticide and venereal disease.
Nonetheless, it seems clear that the Romans did not so much conquer Greece as to occupy its shell; that the Germanic tribes did not so much conquer Rome so much as to move into what remained of it; and that the Arabs did not so much conquer the Byzantine hinterland as migrate into it. On this last point, a new book by Yehuda Nevo and Judith Koren argues convincingly that the Byzantines ceded frontier territories to Arab foederati in the mid-seventh century and that the famous battles of the Islamic conquest in fact never took place.  In one form or another the antecedents of Western civilization died of existential causes, rather than external ones.
No doubt Diamond’s Greenlanders wished to keep on living. They ate their dogs when other food ran out (although apparently they continued to refuse fish for reasons that are hard to explain). Perhaps the will to live among 17th century Easter Islanders burned brightly as they chopped down their last palm tree. It is hard for us to fathom, for we have very little in common with the Easter Islanders. But we have a great deal in common with the residents of classical Greek polis and with the Romans as well as their Byzantine offshoot.
 Crossroads to Islam, by Yehuda D Nevo and Judith Koren. Prometheus: New York 2003.