Conventional wisdom seems to attribute the North American extinctions of the mammoth, the woolly rhino, and the horse to human invasion about 12,000 years ago or so. Some thoughtful folks have wondered about that. Did spear-wielding Asian immigrants really overhunt the American landscape? Chet Raymo passes on this post from last week suggesting that climate change might have had a bigger say in who lived and who died. Citing a study published in Nature:
The coincidence of the extinction of many large animals with the arrival of humans has long been taken as evidence for human overkill, a terrible and decisive slaughter as humans armed with bladed spears and hurling devices moved down across a pristine continent, a truly catastrophic consequence of global warming.
But (R. Dale) Guthrie thinks the evidence for human overkill is not so clear cut. He thinks the extinctions and human arrivals might be separately related to climate change. During the transitional period from ice age to post-ice-age it seems (from the graph) that bison and elks flourished, perhaps sufficiently altering the landscape to the detriment of mammoths and horses. Meanwhile, humans drifted into the Americas with perhaps less decisive impact than formerly believed.
Still, the graph looks gravely suspicious. Have we unfairly implicated our ancestors in one of the great ecological disruptions of all time? Or are they unfairly condemned by coincidence?