If courage makes it significantly more likely that small bands of tribes-men will win military confrontations with their neighbours, its overall advantages can easily outweigh its risks, a mathematical model has shown.
Some men who carry genetic variants that promote bravery might perish because of them, but the ones who survive may win more battles through their greater daring. The resulting opportunities for rape and pillage can create a net evolutionary benefit.
The study is published in The Proceedings of the Royal Society, but it doesn’t look like it’s online yet. So I’ll have to wait on the details, but it what they’re describing seems like group-level selective events which might be vulnerable to “cheaters” who attempt to hold back and allow others to “bite the bullet,” so to speak, and reap the glory that goes to victorious tribes. Multi-level selection theorists such as David Sloan Wilson would make the argument that the way humans work against these “cheats” is through complex cognitive adaptations which allow for the policing of these anti-social traits, as well as the conventional rise and fall of groups who go through a life cycle of vigor, decline and dissipation.
I am still skeptical of higher than individual level selection in general, but, I am becoming less and less skeptical in terms of humans. I think in many ways our complex sociality is atypical enough to warrant the explanations of higher level selection and dynamics. Peter Turchin, Robert Boyd, James F. Crow and L. L. Cavalli-Sforza have also convinced me that we need to take these ideas more seriously for humans.