Two terms are critical here: “kin selection” and “reciprocal altruism:’ Kin selection means self-help by way of natural selection. But in this paradigm natural selection operates not at the level of individuals but at the level of genes. It is the genes that are programmed to perpetuate themselves, even if we—their survival machines—perish in the process. Richard Dawkins masterfully develops this argument in his book The Selfish Gene.
By this logic, a mother who dives into a burning car to save her two children trapped inside is not acting out of pure altruism. Her children share her genes, and her actions are best explained as an effort to ensure that her genes make it into the next generation. Even if she dies, her genes live on through her children. The power of “kin selection” is that it helps to explain why we take big risks and make big sacrifices for our immediate family: they are genetically closest to us. We take smaller risks and make smaller sacrifices for cousins and other relatives: they too are genetically tied to us, but more distantly. Biologist J. B. S. Haldane once quipped that he would be willing to sacrifice his life for “two brothers or eight cousins.”
What about strangers? Darwinian theory says we should be indifferent to them because they are genetically alien to us. Even so, we do trade with strangers and coexist with them and generally treat them decently and fairly. The Darwinians explain this as a consequence of “reciprocal altruism,” which is the moral equivalent of “I’ll be nice to you, so that you will be nice to me.” This strategy can take various forms—”first be nice to me, and then I’ll be nice to you” or “I’ll continue to be nice to you as long as you are nice to me”—but the general idea is that morality is a strategy we employ for our own long-term benefit. Darwinians go to elaborate lengths to establish these strategies, resorting to game theory and obscure analogies from the behavior of ants and vampire bats, but I don’t need to reproduce those arguments; the underlying logic is clear and persuasive enough.