Fortunately, the internet has done it for me. An Evolutionary Theory of Right and Wrong is about just this, but it looks more at proof for innate and inexplicable morals that cross all socio-cultural barriers. Because it’s a newspaper article, it’s not very heavy on explanation, and there’s one point I want to elaborate on.
Many evolutionary biologists frown on the idea of group selection, noting that genes cannot become more frequent unless they benefit the individual who carries them, and a person who contributes altruistically to people not related to him will reduce his own fitness and leave fewer offspring.
While this is true, it’s not applicable. In human tribes or chimpanzee troops, almost everyone is related somehow. There are decent odds that if you give your life to save another, that other will share many of your genes. If that other has more reproductive potential than you, then your genes actually benefit from your death (save the children!).
However, very little altruism involves total self-sacrifice. Even from a selfish gene point of view, diminishing your ability to survive by, for instance, giving food to another group member, would be extremely advantageous if he shares some of your genes and if he needs the food much more than you. Combine this with the fact that almost everyone in groups is related, and charity is beneficial.
“Nature, red in tooth and claw” this is not.
Even without looking at selfish genes, morality is an expected outcome of Darwinism. Every act that’s commonly labeled as immoral is also one that is extremely harmful when common in a group. Would a group of murderers, liars, thieves and rapists survive well? Would a group put up with a member who stole mates, cheated, didn’t repay debts, and attacked others for no reason? Given this, why is it surprising that an animal that lives in groups finds these things unacceptable? It shouldn’t be, because no group can function when anything but a small minority of members behave like criminals.
The plain truth is that most people don’t lie, cheat, steal, kill, or hurt because we’ve evolved in a situation where all of those things would be detriments to our survival in ordinary circumstances. One of the biggest tools evolution has given us to determine what is moral is empathy. But that’s a topic for another day.