You responded to me by making exactly the error I warned about.boris said:
Just because there is still conflict today, a lot of it barbaric and horrible, does not mean there is as much conflict as there was 100 years ago.
Most conflict today is localised and internationally and socially frowned upon. That's a significantly different situation to 100 or 50 years ago. It's also important because it indicates there's a trend towards less violence: once you solve each of those conflicts in Africa, for example, you've pretty much solved them permanently. The world is, importantly, far more politically stable than at any previous point in history.
Iron: Yes, we're still aggressive and competitive. But we've generally learned to channel that into innovation and economic competition instead of senseless war, agreed? I think it'd be frightful if we ever lost our basic sense of aggression.
Although as an example of how levels of aggression can be dramatically altered by environment, without any evolutionary changes, I present you with http://en.wikipedia.org/wiki/Feral_child
Looks like epigenetics at work to me. We always knew the brain changed itself (often permanently) based on the environment, though. Gene regulation and such.