I think we need to distinguish between a "survival mechanism" and "enjoyment of combat".
How are we going to distinguish between the two (assuming we both accept evolution). Enjoyment of combat has developed in several species and clearly has survival value.
I doubt that peaceful co-existance has survival value (although I concede it may have value in some environments). For as far back as we can study-- disparate groups of human beings have been fighting each other. Even our primate relatives (Gorillas, chimpanzees, etc.) fight each other.
Groups of animals fight for a couple of reasons--
First they need to compete for resources with members of their own species as well as other species. Without resources (and the willingness to fight for them) a group will die along with whatever gene they carry. (I don't think I need to show the link between "enjoyment" of combat and willingness to fight... enjoyment is a evolutionary trait to get us to do things that will help us survive).
Second, combat is itself a selection mechanism-- the strong reproduce, the weak don't. Incidently-- combat is one of the reasons we developed such big brains (and why we are able to have this conversation right now).
(Disclaimer... scientific facts about our evolutionary behavior have absolutely nothing to do with any system of morality.)