Another interesting piece of evidence comes from island survivals. If megafauna extinctions were due to climate change, and not human "overkill", one would expect island species to go extinct contemporaneously with their mainland cousins. This is not the case, however. Mammoths persisted on Wrangel Island until merely four thousand years ago. Coincidentally, this is also roughly when humans first arrived on the island. Again, ground sloths became extinct on mainland North and South America from maybe 11,000 to 8,000 years before present, during the time when paleoindians first settled the hemisphere. However, humans didn't have the boats and navigational skills to reach the Caribbean until 4,000 years ago, which is about when ground sloths and other large animals became extinct there. Meanwhile, large animals on islands like Madagascar (elephant birds, giant lemurs, giant tortoises, pygmy hippos) and New Zealand (moas, giant eagles) never suffered
extinction until a mere thousand or less years ago, because people didn't arrive there until that time.
I'm not going to argue that the entire array of megafaunal extinctions was entirely due to anthropogenic reasons, the evidence is not that strong. But overall, I think that Pleistocene/Holocene hunter gatherers had a more pronounced effect on ecology than we've tended to give them credit for, especially in the environmentalist left.