It has taken me a while to work out how to write this piece, I don't really buy the idea that humans had a hand in or were a major cause of the mega faunal mass extinctions at the end of the last Ice Age. I can, however, see the merit in both cases it has therefore been hard to write a damning dismemberment of the "human agent" cause of the mega fauna extinctions at the end of the Ice Age.
The central idea is that humans entering North America encountered mammoths which they then killed and ate in such numbers that either they wiped them out by reducing their numbers to so great an extent that the population became unviable or, in a more moderate version, caused a great stress among the population that led to it being unable to survive environmental shifts. Computer models both prove and disprove the hypothesis which obviously can't be tested for real. There are variants of the theory for Australia and then more recent variants involving island populations being devastated by the arrival of farming peoples.
Like all controversial theories there are believers everywhere and it would appear that the human agent hypothesis is quite well accepted among the general population if not the scientific one. The American and Australian theories both rely on the first peoples arriving on the land mass at or near the time when the mega fauna became extinct. North American archaeology has a fine tradition of people's careers and even lives being ruined as the date for human settlement was put further and further back into time. Recently DNA evidence from Native Americans has cast the peopling of North America back to the Solutrean some 10-15,000 years earlier than thought.
Archaeologically the first peopling has recently been set back by 800 years with the dating of a dart point embedded in a mastodon bone. Evidence they were hunted, of course, but is it evidence they were hunted to extinction?
"Together, the three sites provide strong evidence for pre-Clovis hunting. "They're incontrovertible," said Waters. "Clearly, people were hunting mammoths and mastodons again and again, playing a part in their ultimate demise." Hunted to extinction over (at least) hundreds and hundreds of years, c'mon.
When predators are introduced to an eco-system there can be considerable turmoil while a balanced state will be achieved this can include massive reductions in some animal populations, increases in others and changes in the flora too. Indeed Elephants are considered to be creators of Savannah environments. Due to the massive rate of tree consumption the loss of mammoths from an ecosystem would cause widespread disruption and even possible extinctions. This gives us a mechanism for the mass extinctions at the end of the Ice Age in North America. If the creator of an ecosystem goes then so does the eco-system the lions, camels, giant sloths, horses etc.
In Australia the mega fauna extinction is co-incident with charcoal deposits left presumably by the first Aborigines to reach the land mass. The list of animals is smaller and their disappearance co-incides with non climate caused changes in vegetation. A later arid spell may have finished many off, but it is thought that the Aborigine practice of setting fires could have changed the environment to the point where the larger animals would have died off. As far as I know there is no evidence of direct predation. Again there are proponents suggesting that climate change caused by glaciation was the cause and that the change in vegetation was because the mega fauna disappeared not the cause of the disappearance.
So there we have the only theory that really makes sense is mass floral eco system disturbance causing a catastrophic disruption of the whole ecosystem. Large animals are far less resistant to environmental degradation and are the usual candidates for extinction in any mass extinction event. The agent could be either climate change or human predation of animals which create eco-systems. There are numbers of variants of all theories and computer models galore.
It is interesting to me that in Europe at least the idea of climate caused extinctions is not that contentious. Humans co-existed with mega fauna for immense periods of time in the old world, sometimes hunting them (neanderthal) sometimes not (sapiens in W.Europe). There is little evidence of active predation across Eurasia though some evidence of possible consumption in eastern Europe and almost certain consumption (through scavenging) in Siberia. In western Europe at least there is no evidence of mammoth being on the menu with ungulates and other large herding animals being the prey items of choice. Mammoths are supposed to have become extinct through environmental changes at the end of the ice age with late survivals in the UK.
This to me is the main problemflaw in the human agent hypothesis, that mega fauna populations collapsed world wide in areas where there were humans hunting, not hunting or even not being present. I think that the human agent hypothesis is anthropocentric and myopically ethnocentric. I don't mind if you think me romantic or accuse me of having "rose tinted" glasses the evidence ,or lack thereof speaks for itself , there are few if any hunter gatherer models for animal extinction from modern scientific descriptions or historical accounts. There are plenty, plenty and plenty more from agricultural populations and the industrial revolution has proven a veritable animal holocaust.
This in my view is the central point of the human agent hypothesis, our culture has a long history of hunting animals to destruction. The wolf has hung on by the skin of it's teeth as has the bear, tiger etc. The auroch is long gone as is the Tasmanian wolf, passenger pigeon, and scores of others. The last hundred and fifty to two hundred years saw a massive extirpation of wildlife in the continental United States and this surely has coloured the view of the mega faunal mass extinctions.
Guilt, cultural guilt is,to me, the father of the human agent hypothesis, established,diverse balanced ecosystems utterly destroyed and replaced by a sterile monoculture, moreover it is the cultural guilt over the genocide of the indigenous peoples. The human agent hypothesis is strongest and most emotionally charged in the two countries which saw a systematic,and ruthlessly executed genocide of the indigenous people by the current dominant culture.
"We may have wiped out the passenger pigeon but they killed all the mammoths."
It does not really matter if the paleoindian or the Aborigine or even the Ice Age European did wipe out the mega fauna, I wrote this post as I was really angered by a comment someone had made on a youtube film about Inuit cooking "it's 2012 stop eating animals save the world go vegan". The Inuit lived and live in balance with their environment, life was hard we might not wish to live like that but even with their extraordinary reliance on animal resources the traditional culture was totally sustainable and could have continued in that ecosystem forever. Steffanson was concerned in 1906 that the rifle would destroy them (as it made hunting too easy) but it appears not. The Hadza are not causing the scarcity of game (for which they are blamed) in Tanzania and again could continue to live there forever unlike the onion farmers who are chopping down trees and ploughing up the land. The Indian may have wiped out the mammoth but the land Europeans described when they came to stay and farm was a land of unparallelled natural abundance compared to the man made deserts they had left behind.
This is the story of the human agent hypothesis, like all predators humans may kill beyond their need and have a dramatic affect on their ecosystem stories of the proto-environmentalism of hunter gatherers never really stand up to scrutiny. The difference is that they do achieve equilibrium, a balance with the ecosystem. The continued rapacious destruction of ecosystems and fauna is the legacy, indeed the need, of agriculture.
Farming hates wildlife, in the UK there was an all out war against the wolf, woods and wastes were burnt and all manner of financial incentives were used to achieve their destruction. The last wolf in the UK was killed in Scotland in about 1746 it took well over 1000 years to do this. The part of the country with the least land under cultivation, wild and barren the Scottish mountains appear to be a veritable Serengeti compared to much of the UK mostly due to the hostility of the land to arable farming. Steffanson put the survival of the boreal north and the Indians there down to its hostility to agricultural. The plains were too fertile so the buffalo and indian had to go. Now the plains are fertilised by petroleum derivatives and the topsoil silts up the rivers, paradise lost.