How war factors into evolution

War is a "solution" that nature came up with to deal with the problem of deciding which society should be allowed to use resources and which should not. Humans have tribal warfare instincts (so do apes). Tribal warfare "works" (in a totally amoral way) because it selects groups that mentally and physically out-perform others. Without this pressure, humans may not have evolved to become more and more intelligent to the point they have reached today. The problem is that tribal warfare insticts mixed with modern nuclear weapons is not what nature intended or tested. The bombs just kill everybody without selecting the fittest for survival. It's fortunate that somewhere in our minds nature also gave us some kind of global respect for human life - which is probably what stopped the the Cuban missle crisis from turning into WW3. However, I really don't think that global respect is very strong on average - because it never needed to be while our instincts were evolving. We have not yet been through the evolutionary pressure required to select for global respect for life. Consider 100 human-level species on 100 different planets. The societies that have sufficient respect continue to exist while the ones without it bomb themselves into nuclear winter. We either are one that survives or not. (This is very different from tribal existence thousands of years ago where pretty much only repect toward the tribe members counted.)