An interesting observation from Richard Joyce’s The Evolution of Morality, which I’m currently reading:
If human reproductive fitness was enhanced by a proclivity for helping family members (the degree of help being roughly proportional to the degree of relatedness), what might the process of natural selection have done to our brains in order to accomplish this? An important part of the answer, I think, is clear, simple, and rather agreeable: love. Mothers and fathers love their children, siblings love their siblings, uncles and aunts love their nieces and nephews, and so on. We could argue endless over what species of thing love really is, but let’s just plump for the natural answer and say that it is (perhaps among other things) an emotion.
Joyce is trying to get at the evolutionary reason for what he terms human “helpful behaviors” — those which benefit others. The mechanism natural selection worked on, he guesses, was already there in mother love. Kin love would be flow from this source, and so would man-woman love, love of country, love of pets, and if such a thing is possible, universal love.
If Joyce’s hypothesis is true, then the evolution of human morality is a case of love conquering all. Now, I’m a non-romantic by nature. Life is short, and gushing consumes an inordinate amount of time and energy. Still, I wouldn’t be surprised if Joyce turns out to have guessed correctly about the source of our moral emotions. And, beyond Darwinism and natural selection, it’s a theory any Jeffersonian can endorse.