This, and going back further, people literally would brutally massacre neighbouring tribal groupings over control of fishing and hunting and gathering grounds.

This, and going back further, people literally would brutally massacre neighbouring tribal groupings over control of fishing and hunting and gathering grounds. The rapid dispersal of our species over literally the entire planet (minus Antarctica) likely also has a lot to do with constantly moving on to new opportunities further away from rivals. That said, starting in about the 18th century we ran out of new places for that. And intensification truly began.