LONDON — “The survivors are scraps,” says evolutionary biologist Dr. John Alroy about the large mammal species that remain in North America after the wave of extinctions that followed the arrival of the first humans less than 14,000 years ago. And there is no longer any question about why all the rest — mammoths, mastodons, giant sloths, camels, horses, giant armadillos, and deer the size of moose — died out. In his article in this month’s Science, Alroy puts the blame firmly on human beings.
Paul Martin of the University of Arizona first raised this “New World Blitzkrieg” theory back in 1967. It has always been puzzling how many more big animal species there are in Africa, Europe and Asia, where humans and their immediate ancestors have lived for hundreds of thousands of years, than in the Americas and Australia, where they arrived all of a sudden and relatively recently. Martin suggested that it was because the Indians and the Australian aborigines killed them off — and unleashed a firestorm of protest.
The angriest protesters were the North American Indians themselves, who felt they were being robbed of their last shred of cultural dignity. They had lost their land, their future, and in many cases even their language to the European invaders. About their only consolation was their belief that they had some special spiritual status as the stewards of the land; that they were people with a special gift for living in harmony with nature.
Now the damn Europeans were saying that it was their ancestors who killed off 32 of the 41 large plant-eating species that lived in North America 15,000 years ago (plus, indirectly, several large carnivores that used to live off of them). It was just too hurtful to be borne, so they rejected the evidence — and so did many non-native scientists who were unhappy about this vision of Man the Exterminator.
So the theory was roundly condemned, and a generation of academics tried to refute it with implausible theories about how climate change or disease or some other non-human cause triggered these extinctions. The “controversy” ran on for decades.
And now, into this orgy of Indian self-righteousness and white guilt, steps Dr. John Alroy, to point out that the emperor has no clothes. He will doubtless regret it.
The extermination of most large land animal species within a few thousand years of the arrival of the first human beings in North America, says Alroy, was inevitable. He offers a simple computer simulation based on how early human beings hunted and traveled, and where the animals lived and how they reproduced. No matter how you adjust the variables to make the people worse hunters or the animals more prolific breeders, most of them die out.
A companion article in the same issue of Science documents a similar episode of mass extinction in Australia 46,000 years ago that seems to have human causes. People in these new environments not only found animals who did not fear them and were thus very easy to hunt; they also set huge fires to open up the landscape and destroyed the animals’ habitats. They were seriously into overkill, but as Dr. Alroy says, it was “an ecological catastrophe that was too gradual to be perceived by the people who unleashed it.”
Never mind the sententious moralizing that normally ensues at this stage of the discussion. The more important point is made most clearly in Jared Diamond’s brilliant book “Guns, Germs and Steel.” It is that ecological destruction is its own punishment.
The newly arrived hunters in the Americas and Australia were no more efficient or less intelligent than their ancestors in Eurasia. They were just up against species that had not evolved with human beings, like those of the Old World, and thus had no inherited fear of them. So they quickly killed most of the larger species off — thereby eliminating precisely the animals that might later have enabled them to build civilizations able to rival those of Eurasia.
The irony is brutal. Early civilizations in Eurasia depended on domesticated animals, but the “New World blitzkrieg” exterminated all the leading candidates for domestication in the Americas and Australia long before the local people started down the road to civilization.
When they did start down it, in places like Mexico, the central Andes, and even the Ohio Valley, they moved far more slowly because they had almost no domesticated animals: the horses, camels, mastodons, wild pigs and the like were all gone long ago. And so the New World civilizations were eventually overwhelmed by Europeans whose civilizations grew faster thanks to horses, cows, sheep, pigs and goats.
Nobody understood what was happening. Nobody was to blame. And if you want a parable for our own times, make it up yourself.