Why were prehistoric era animals so gigantic in comparison to animals from the “modern era”

Question

Why were prehistoric era animals so gigantic in comparison to animals from the “modern era”

In: 1281

Answer 1

It is explained pretty well in Sapiens book. Basically, instead of asking why they existed back then, you should ask why they do not exist now. In prehistoric era all kinds of animals existed, gigantic and small. However, most superfauna has been exterminated by… humans. The more we developed our means, the farther we started to travel and our population grew. The bigger the animal is, the easier it is to hunt it down, so humans prioritized them. It is said that Australia used to have 90 species of megafauna which was limited to ~5 within decades after homosapiens arrival.