Conservation is hard, Greg Cochran notes — but so is driving a prey animal to extinction:
Even if the population as a whole would be better off if a given prey species persisted in fair numbers, any single individual would benefit from cheating — even from eating the very last mammoth.
More complicated societies, with private property and draconian laws against poaching, do better, but even they don’t show much success in preserving a tasty prey species over the long haul. Considers the aurochs, the wild ancestor of the cow. The Indian version seems to have been wiped out 4–5,000 years ago. The Eurasian version was still common in Roman times, but was rare by the 13th century, surviving only in Poland. Theoretically, only members of the Piast dynasty could hunt aurochsen — but they still went extinct in 1627.
How then did edible species survive in pre-state societies? I can think of several ways in which some species managed to survive voracious humans, but none of them involve green intent.
First you have to realize that driving a prey species to extinction is unusual: it doesn’t happen often with normal predators. Specialized predators obviously can’t do it — when their prey gets scarce, so do they. On the other hand, unspecialized predators generally won’t be as efficient. On the gripping hand, at any given moment, a predator and its prey have been co-evolving (and co-existing) for millions of years. Both are highly optimized — which means that further improvements would be difficult — and it shouldn’t easy for the predator to suddenly develop a crushing superiority. This argument doesn’t apply to newly introduced predators, of course.
Mass extinction is even less likely, because even an unspecialized predator should become rare when the total amount of prey (all relevant species) goes way down.. Unless this potent predator is really an omnivore — but that means even less specialization in predation. Omnivores (bears, for example) usually aren’t that effective.
If we go back far enough, protohumans simply weren’t very good hunters, because they weren’t smart. Lions manage to be pretty good predators without being particularly smart, but humans, who don’t have impressive natural armament, have to succeed in hunting through tools and social cooperation. They were probably death on turtles early on, but in general early humans advanced slowly, giving prey species lots of time to adapt — African and Eurasian species, that is.
The pace of innovation gradually increased, and I can think of some species in Africa and Eurasia that were probably ganked by humans a long time ago — but it wasn’t dramatic. Progress in hunting, new tactics and weapons, was still slow enough to allow adaptive response in prey species. Consider the Neanderthals: I can’t think of a single species they wiped out. Wimps.
By the Upper Paleolithic, modern humans were innovating much more rapidly, and human-driven extinction starts to become really important. It wasn’t just better hunting that mattered. Better food preparation — getting more out of each carcass — increased human density, and thus hunting intensity. You might think that greater efficiency would mean that we didn’t need to bring down as many beasts — not so, in a Malthusian world.
Developing new ways of gathering food other than hunting, such as fishing and better preparation of plant foods, meant that human density could stay high even as mammal biomass crashed. Innovations in clothing and housing let people colonize the high Arctic, and eventually the Americas. Invention of boats and rafts led to the colonization of Australia and numerous islands.
We were omnivores and generalists: population collapse of prey species couldn’t stop us. We could kill anything — but the biggest threat of extinction was to large animals, which were worth a lot (mucho calories for the tribe) and bred slowly. Worst off were those animals that had never had a chance to adapt to humans.
There were some modifying factors. It probably wasn’t just adaptation to humans that saved much of the African megafauna: African pathogens may have played a role too, keeping human numbers down and possibly even creating natural game preserves (I’m thinking of sleeping sickness). Contrariwise, Australia and the Americas were almost disease-free, as far as humans were concerned.
War is bad for us, good for our prey. The no-man’s land between hostile tribes is oddly full of game, since people are afraid to go there. In much the same way, rabbits flourished next to the Berlin Wall, while Asiatic black bears and musk deer inhabit the Korean DMZ.