Steven Pinker, evolutionary psychologists extraordinaire, has an article in the New York Times called The Moral Instinct about evolution and, what else, the moral instinct.
It it he talks about morality and how our sense of moral outrage at certain things is a function of an evolved sense, though it isn't clear if he means this in a literal manner or figurative. He repeats all the experiments and research that has been done, and then jumps to conclusions. Again, he is an evolutionary psychologist, which means that evolution must obviously have a role in everything. Of course, the role of society is left on the wayside.
"The stirrings of morality emerge early in childhood. Toddlers spontaneously offer toys and help to others and try to comfort people they see in distress. And according to the psychologists Elliot Turiel and Judith Smetana, preschoolers have an inkling of the difference between societal conventions and moral principles. Four-year-olds say that it is not O.K. to wear pajamas to school (a convention) and also not O.K. to hit a little girl for no reason (a moral principle). But when asked whether these actions would be O.K. if the teacher allowed them, most of the children said that wearing pajamas would now be fine but that hitting a little girl would still not be."
Of course, children are socialized heavily by this age. Were they not, they would not understand that wearing pajamas to school was wrong, just that hitting others was.
This is not to say that biology and evolution play no role in our actions, moral or otherwise. Obviously they do. But, claims such as Pinker's seems to be stretching the evidence. It seems clear that there is some sort of biological basis for altruism, at least to the extent that our brain allows for it through socialization. But there is also a biological basis for selfishness, as evidenced by its existence.
Another problem is how Pinker thinks this affects our idea of what is moral. In all honesty, he isn't very clear about why the knowledge of why we act moral and why we think something is moral helps us in determining what is moral. Certainly he makes a case that it helps us understand the actions of others, but that doesn't require evolutionary psychology, just some social science. This is not a shortcoming he alone possesses. This is a fundamental problem that ethical naturalists have.