The extinction of the Pleistocene megafauna is itself a topic of ongoing debate, with two main hypotheses competing for primacy.

The climate change hypothesis proposes that the rapid warming and environmental transformation at the end of the Last Glacial Maximum — the replacement of the productive mammoth steppe by the less productive boreal forest and tundra environments that characterize much of the northern hemisphere today — reduced the habitat and food base for the large herbivores of the mammoth steppe, driving them to extinction through a combination of habitat loss and reduced reproductive success.

The overkill hypothesis proposes that the hunting pressure from human populations, as they spread across the Americas and other continents, was the primary driver of megafauna extinction.

Under this model, the large herbivores of the Americas, having evolved without any experience of human hunters, were naively approachable and could be hunted more easily than the African megafauna, which had co-evolved with human hunters for millions of years.