As long as there have been scientists, they have been interested in goodness. Why are some people good, and others not? In fact, we can cast the net more generally, and ask about goodness in nonhumans, as well as humans, and examine whether the process of evolution by natural selection can explain such actions. I talk about this at length in my new book, The Altruism Equation: Seven Scientists Search for the Origins of Goodness (Princeton University Press, 2006), but here is a condensed version of the story.
Evolutionary biology's interest in goodness can be traced back at least as far as Charles Darwin. It is hard to image that anyone could think of goodness as a problem, but Darwin did. He saw the little worker bees that sacrificed themselves to protect their hives─the ultimate example of animal altruism─as especially troubling to his theory of evolution by natural selection. Darwin said the bee's behavior drove him "half mad." If his ideas on natural selection were correct (and, of course, they were and are), then this sort of altruism should be extraordinarily rare in nature. How could sacrificing one's life ever be favored by natural selection? If increased reproductive success is what drives the evolution of behavior, then altruists should disappear─and fast. But, in the case of the bees, they didn't disappear, and Darwin was so puzzled by this that he spoke of altruism as "one special difficulty, which at first appeared to me to be insuperable, and actually fatal to my whole theory."
And then a solution to this nasty conundrum hit Darwin like a ton of bricks. Worker bees weren't being altruistic for just any old bunch of bees, they were protecting individuals in their hive. And their hive contains a special class of individuals─blood relatives. Blood relatives are by definition genetically similar to one another, and so even though worker bees may have been giving up their lives, they were potentially saving the lives of hundreds of blood relatives by doing so. Darwin didn't know about genes per se, but he did know that something like what we'd call genes were passed from parents to offspring and shared by blood relatives, and that this was enough to solve the problem of altruism. In modern language, we'd say that the workers bees were indirectly saving copies of their own genes─copies that just happen to reside within their blood kin.
Darwin wasn't the only 19th century scientist who was enamored with the question of the evolution of goodness. His dear friend, Thomas Henry Huxley--arguably the most famous scientist in all of Europe--was as well. Huxley, in fact, got himself into quite a heated argument over whether blood kinship could or could not explain altruism. His opponent was Peter Kropotkin, a former chief page to the Czar of Russia, naturalist, and the most famous anarchist of the 19th century. Huxley argued that all goodness could be traced to blood kinship, while Kropotkin proposed that goodness and blood kinship were completely divorced from one another─one had absolutely nothing to do with the other. Of course, neither was right, but it would take almost a hundred years before a shy, reserved, and brilliant British biologist named William D. Hamilton would settle all the arguments about blood kinship and altruism with a nifty little mathematical equation.
Hamilton, an evolutionary biologist by training, came at the question of altruism and blood kinship the way that an economist would; indeed his Ph.D. in biology was done in part at The London School of Economics. He began by defining three terms─the genetic relatedness between individuals (labeled r), the cost of an act of goodness (c), and the benefit that a recipient obtained when someone was nice to him or her. Then, using some eloquent--in fact, beautiful-- mathematics, in 1963, Hamilton found that altruism and blood kinship are not linked by an all-or-nothing relationship. Instead, what is now known as "Hamilton's Rule" states that altruism evolves whenever r times b is greater than c. In other words, if the cost of altruism is made up by enough genetic relatives receiving benefits, then altruism spreads; otherwise it does not. Phrased in the cold language of natural selection, relatives are worth helping in direct proportion to their genetic relatedness.
Literally thousands of experiments in both nonhumans and humans show the power of Hamilton's Rule. This little equation is evolutionary biology's version of e = mc2. Over and over, we see that an analysis of the costs and benefits of altruism, along with genetic relatedness, allows us to predict the presence or absence of altruism. This is a truly remarkable finding.
Hamilton's Rule, of course, does not explain all altruism, nor did Bill Hamilton think it did. Another large chunk of goodness falls under the category of reciprocity--you scratch my back, and I'll scratch yours. Individuals are sometimes willing to be altruistic to someone now in the expectation that they will, in turn, be helped when they need it. Evolutionary biologists have been almost as interested in this type of altruism as in kinship-based altruism. And, amazingly enough, it was Bill Hamilton, along with political scientist Robert Axelrod, who formalized the models behind the evolution of reciprocity. Following up on some work done by Robert Trivers in the early 1970s, in 1981 Axelrod and Hamilton used a mathematical technique called game theory to predict when "reciprocal altruism" should evolve. Again, scores of empirical studies followed up the model. Reciprocity can be complex, but an evolutionary perspective has cleared the haze here the same way it did when it came to blood kinship and altruism.
If goodness is a problem, then the answer─or at the very least, part of the answer─can be found in evolutionary biology.