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

Humans seem to have killed off the biggest animals available first almost everywhere they went. Gigantic animals everywhere was more or less typical for most of the fossil record. Then some bastard invented the spear. It’s a miracle that elephants and lions are still with us.