We survived by protecting our own, and generally by out competing our neighbors, at least until we figured out trade. We, culturally, have benefited from the longest period of peace that humanity has a whole has seen for entirety of human history, due to developing the most advanced and destructive weapon we could figure out. Bias against killing our kin? Like 90% of scientific advancement is finding better ways to kill, or at least get advantage over, our kin.
We can't even stop arguing and fighting long enough to halt the destruction of our habitat, which we know definitely will kill us all.