A reader puts it more bluntly:

This should probably go to Derb, but your email addy is easier to get, so… Why is Derb assuming that natural selection would select for children developing into behaved adults, in the absence of one or both parents? Wouldn’t a cutthroat, thieving scoundrel do better at surviving in such circumstances to pass on his genes, especially since most of our evolution has occured in the nasty, brutish, short phase? I don’t see how adult behavioral dysfunction prevents a rapist from reproducing. It seems to me Derb is assuming that well behaved, well adjusted, sociable individuals are a “goal” of natural selection, but that doesn’t follow.