Human nature is vicious and predatory.

“I don’t believe that on this earth men, who are wolves preying on their fellow men, will attain global peace. Basically, Fukuyama was thinking about this peace with his idea of the end of history, but recent events have shown that history repeats itself, and always in the form of conflict.”

--Umberto Eco, Some Reflections on War and Peace, Turning Back the Clock.

‘What those people who trot out the jungle analogy really mean, but don’t say because it sounds too pessimistic, too predestinarian, is: homo homini lupus. We cannot collaborate because human nature- leave aside the nature of the world – is fallen, vicious, predatory. (The poor, maligned beasts! The wolf is not predatory upon other wolves: lupus lupo lupus would be a slander.)

--J.M.Coetzee, Diary of a Bad Year.