Why did large animals go extinct in north america?

Pleistocene megafauna is the set of large animals that lived on Earth during the Pleistocene epoch and became extinct during the Quaternary extinction event. Megafauna are any animals with an adult body weight of over 44 kg (97 lbs).

Faith's findings support the idea that this mass extinction was due to human overkill, comet impact or other rapid events rather than a slow attrition.