Look I think we both believe the same thing overall but for whatever reason we're not meeting up in the same space.

But you are suggesting violence wasn't common and hunter-gatherers didn't engage in it when history tells a completely opposite story that violence was pretty steady. As much as people would cooperate, the also fought. It really depended on resources, and resources were thin. The periods of violence weren't brief, they were common, everyday and existed alongside peace basically in a duality. We have proof our ancestors likely integrated with neanderthals, we also have proof the two probably beat the shit out of each other. Things aren't black and white they're always grey.

I do think humans are innately violent and selfish, but I think you're viewing that phrasing in our society's lens. Violent and selfish to us typically means violence and selfish towards our fellow countrymen, neighbors, allies. But we're not talking about towns and cities of millions, we're talking about clans and cultures of maybe a few hundred tops. They likely viewed their own much closer, but when it came to outsiders they were in competition for resources with, they had to be selfish and likely were willing to be violent for their own people. It isn't the same individual selfishness, it is more of a "me and my people" selfishness that you can still see today with racism, nationalism, weird cultural identity issues. We find skeletons with signs of trauma all the time suggesting violence was constant for these people, raids and clashes were common. You had to fight for what you needed quite literally.

Today we see how much education is a decider in how selfish people are, those who can understand society and view people with empathy and understand how that fits in tend to engage in it more. For most of human history there were less people on the entire planet than in my area alone, I live amongst maybe 9million people. That's massively more than the entire planet housed for thousands upon thousands of years. And the fact we don't fight, aren't violent and work everyday together shows we have deincentivized violence massively and for the better. Society today is more altruistic, we are the kinder people. But in our hearts and minds still exist the ancient selfish and violent human.

Capitalism doesn't discourage cooperation at all, as much as we might have issues with our society, capitalism and beyond has actually brought about massive cooperation so that we exist in far greater numbers and experience less violence than our ancestors did. That shows we are better at cooperating. The last 10,000 years might be a fraction but it is not insignificant. Before the last 10,000 years the population was barely scratching 1 million, today we add roughly 100 million each year. Most people who have ever lived have actually lived in the era of recorded history. That is the significant fraction of human history.