It's because there's conflict between individuals but also between groups. With inter-group competition, the tribe that cooperates better is going to out-compete the tribe that succumbs to in-fighting.
The alarming corollary is that, in the absence of inter-group competition, intra-group competition becomes the only relevant evolutionary pressure. Basically, a society without enemies may be destined to become more selfish over time. This could be the main driving force behind the "inevitable" rise and fall of dominant civilizations.
The big question is: how does one delineate the in-group from the out-group? How can we invent that boundary to minimize conflict overall?
The alarming corollary is that, in the absence of inter-group competition, intra-group competition becomes the only relevant evolutionary pressure. Basically, a society without enemies may be destined to become more selfish over time. This could be the main driving force behind the "inevitable" rise and fall of dominant civilizations.
The big question is: how does one delineate the in-group from the out-group? How can we invent that boundary to minimize conflict overall?