Given that all of recorded history has taken place in the last 10500 years, and that time has seen a huge diversity of social structures in civilizations across the globe, I think your pessimism is unfounded.

Yes, people are selfish. People also have a great capacity for cooperation and altruism, given sufficient cause to bind them together.

I rather hope that the impending collapse of the biosphere that sustains all life is just such a cause. Then again, we appear to be setting the world on fire at an ever greater pace.