There are some things that I think should be included in evolutionary psychology but (as far as I know) aren’t.
From what I’ve read, some personality trait differences between individuals are, in evolutionary psychology, attributed to either a) variance around an optimum or b) adaptation to enhance chances of survival/gene passage for an individual.
It seems to me that they could also have evolved in order to enhance chances of survival of a tribe as a whole.
A few examples:
Some people are naturally late to sleep late to rise. Some are early to bed early to rise. This mixture allows there to be some number of people awake and alert and on the watch for predators/enemies/lightning storms/whatever.
Some people are naturally adventure seeking. They’re not content to sit around the fire. These people pushed the tribe to new areas and perhaps found additional resources before it was too late. But you can’t have everybody in a tribe with that trait, because, among other things, that would reduce the social cohesiveness of the group. Also, you need a large percentage of people who are content to hunt and gather.
Some people are natural raconteurs. This helps the morale and social cohesiveness of the group. Somehow it seems that too many of this type wouldn’t work. Perhaps the audience wouldn’t be so captivated (and hence morale so improved) if it was so common.
Some percentage of people are leaders, others followers. Others lone wolves. This has obvious advantages.
Perhaps nature selected whole tribes for the correct percentage of different personality traits. You have these different personality traits distributed in certain percentages such that the odds of survival of the tribe as a whole are maximized. Tribes that had too many or too few of certain types didn’t make it. And that genetic legacy lives on today.
