Pleistocene megafauna is the set of species of large animals that lived on Earth during the Pleistocene epoch and became extinct in a Quaternary extinction event. These species appear to have died off as humans expanded out of Africa and southern Asia, the only continents that still retain a diversity of megafauna comparable to what was lost. The Americas, northern Eurasia, Australia and many larger islands lost the vast majority of their larger and all of their largest mammals. Four theories have been given for these extinctions: hunting by the spreading humans, climatic change, spreading disease, and an impact from an asteroid or comet, a combination of which is also possible.
Contributions by The way, the truth, and the light, Dakuhippo, and Ethel Aardvark.