Patricia Churchland in The Scientist:
Three myths about morality remain alluring: only humans act on moral emotions, moral precepts are divine in origin, and learning to behave morally goes against our thoroughly selfish nature. Converging data from many sciences, including ethology, anthropology, genetics, and neuroscience, have challenged all three of these myths. First, self-sacrifice, given the pressing needs of close kin or conspecifics to whom they are attached, has been documented in many mammalian species—wolves, marmosets, dolphins, and even rodents. Birds display it too. In sharp contrast, reptiles show no hint of this impulse.
Second, until very recently, hominins lived in small groups with robust social practices fostering well-being and survival in a wide range of ecologies. The idea of a divine lawgiver likely played no part in their moral practices for some two million years, emerging only with the advent of agriculture and larger communities where not everyone knew everyone else. The divine lawgiver idea is still absent from some large-scale religions, such as Confucianism and Buddhism. Third, it is part of our genetic heritage to care for kith and kin. Although self-sacrifice is common in termites and bees, the altruistic behavior of mammals and birds is vastly more flexible, variable, and farsighted. Attachment to others, mediated by powerful brain hormones, is the biological platform for morality. As I write in my new book, Conscience: “Between them, the circuitry supporting sociality and self-care and the circuitry for internalizing social norms create what we call conscience. In this sense, your conscience is a brain construct, whereby your instincts for caring, for self and others, are channeled into specific behaviors through development, imitation, and learning.”
More here.