I find the notion that there was a period of time when we haven't fought ridiculous. We have fought from the day one. I mean, let's consume that smaller ameba. It's genetic.
I figure it went down like this:
"Chief, he took your wife!"
"Let 'im 'ave 'er, didn't like 'er anyway."
"Also, he said you have a small spear."
"Lemme at him!"
(Read in ancient german.)