"As long as the finding of new ways in which to live was left to natural selection, there was always a tenuous peaceful coexistence of the living things on earth. But eventually one kind of animal found it possible to keep occupying new niches at will, always adding the niche-spaces of others to its own, escaping the ancient constraint of a fixed niche that is imposed on all others by natural selection. This animal yet continued to obey the other dictum of natural selection, which is to raise the largest possible number of offspring. The activities of this new form of animal are inevitably hostile to the interest of almost all the other kinds, for it engages in aggressive competition, instead of peaceful coexistence, in its drive for more and more young. It has been carrying on this new way of life for only nine thousand years."

~ Paul Colinvaux, Why Big Fierce Animals are Rare, An Ecologist's Perspective