Final answer:
The extinction of American megafauna occurred after humans arrived in the Americas, with evidence suggesting that human hunting played a significant role in their disappearance around 10,000-12,000 years ago.
Step-by-step explanation:
American megafauna, such as woolly mammoths, giant deer, and saber-toothed cats, went extinct after humans arrived in the Americas. The Pleistocene Extinction, which occurred roughly 10,000-12,000 years ago, coincides with the arrival of humans who were capable of hunting these large animals. As humans spread across continents, they brought with them advanced hunting techniques and tools, which had a significant impact on the local wildlife. In the case of North America, the evidence suggests that the arrival of paleo-humans and the subsequent megafaunal extinctions were closely linked in time.
While climate change has also been proposed as a cause for these extinctions, research indicates that in many cases it was human activity that precipitated the disappearance of these species. Notably, the correlation between human arrival and species extinction is particularly clear in regions where humans were newcomers, such as on remote oceanic islands and Australia. This pattern of extinction following human arrival is less evident in Eurasia and Africa, where humans had been present for much longer.