This, or something quite like it, has become the prevailing wisdom in the field of animal (and plant) behavior. It has considerable explanatory power. At the human level it helps to explain such varied matters as nepotism and the fact that foster children are much more likely (in America, for example, about a hundred times more likely13) to be fatally abused than children living with their natural parents.
The cooperation of the cells in stromatolites and other colonial organisms can be understood as selfish at the level of the gene, since they’re all close relatives. Cooperation of the chloroplast and the cell with which it forms a symbiotic attachment—is this selfish? The cell that eats its chloroplasts is at a competitive disadvantage. It refrains from eating them not because it has even a glimmer of altruistic feeling for the chloroplasts, but because it’s dead without them. It forgoes the pleasures of a chloroplast meal for a substantial future benefit. It exercises restraint on short-term, selfish behavior. It practices impulse control. Selfishness still prevails, but we are made aware of the distinction between short- and long-term selfishness.
For most social animals, and for obvious reasons, the animals you grow up with tend to be close relatives. So if you cooperate, if you show what superficially might seem like altruism, it’s naturally directed toward close kin and can therefore be explained as kin selection. An organism might forego its own replication, for example, and devote its life to improving the chances of the survival and reproduction of close relatives—those with very similar DNA sequences. If all that counts is which sequences will be widely represented in the life of the future, those species with a flair for altruism might do well. They can help ensure that much of their genetic information is passed on, even if none of their atoms wind up in the bodies of the next generation.14
The geneticist R. A. Fisher described heroism as a predisposition inclining its bearer toward “an increased probability of entering an occupation not easily to be reconciled with family life.” Nevertheless, Fisher argued, heroism—in humans or in other animals—might carry a selective advantage by preserving the very similar genetic sequences of close relatives, enabling such sequences to be passed on to future generations. This is one of the first clear articulations of kin selection. Parents sacrificing themselves for a child can be understood on similar grounds. The hero or the devoted parent will be doing simply what feels “right,” without attempting any calculus of benefit versus risk to the gene pool. But the reason it feels “right,” Fisher proposed, is that extended families characterized by conscientious parenting and heroes aplenty will tend to do very well.*
Animals may be willing to make real sacrifices for close relatives, but not for more distant kin. Think of it this way: Imagine sleeping soundly at night, knowing that your children are starving, homeless, or gravely ill. For almost all of us, it would be unthinkable. But forty thousand children die each day of easily preventable hunger, neglect, or disease. Institutions such as the United Nations Children’s Fund are in place that could save these children—with innoculations against illness, with a few cents a day worth of salts and sugar. But the money is unavailable. Other needs are deemed more pressing. The children continue to die while we sleep well. They are far away. They are not ours. Now tell us you don’t believe in the reality of kin selection.
Still, if you find yourself among others of your own species who are not your near kin, surely it is to your advantage to cooperate against a common enemy. You can draw upon behavior evolved for kin selection in order that a group of animals not closely related can cohere and survive.* And if altruism is one of your talents, you might find yourself practicing it even on animals of another species. Dogs are known to risk their lives to save humans—surely no close relatives. Nor does the hope of future reward explain their behavior.
How are we to understand well-attested cases of dolphins saving drowning humans by repeatedly nuzzling them up to the surface and pushing them toward shore? Is the dolphin unable to distinguish the thrashing human from an infant dolphin in trouble? This is highly unlikely; dolphins are discerning observers. What about cases of abandoned or strayed human infants being raised by wolf mothers that have lost their pups, or birds of a different species brooding cuckoo eggs? Why do drivers swerve to avoid hitting a dog on the road, although they thereby put their own children in the back seat at increased risk? What about youngsters dashing back into the burning house to rescue the cat? Such cases of courage and care directed to other species may derive from a misdirected kin selection, but they do happen and they do save lives. Shouldn’t we then expect to find altruistic behavior much more frequently directed toward other members of the same species, even if they’re not close relatives?
Consider two groups, one composed of unrelentingly selfish individualists, the other of solid citizens who are occasionally willing to sacrifice themselves for (even distantly related) others. Against a common enemy, can we not imagine circumstances in which the latter group fares better than the former? Obvious disadvantages also accrue to a community of strict altruists constantly throwing their lives away in order to benefit total strangers. Such a group would not last long—if only because any tendency toward selfishness would quickly spread.
What if there’s a critical size for the group to work? When membership is below some rough threshold, certain functions of the group begin to fail. For example, the bigger the group, the better huddling together for warmth works,15 or mobbing a predator;16 and below a certain size, group benefits become increasingly unavailable. It’s not hard to imagine wholly selfish genes that cause defections from community service—a refusal to mob a predator, say, because it might be dangerous. If these genes proliferate, the point will be reached where almost nobody has the gumption to mob, and the danger posed to everyone by predators has increased. Thus, for longer-term reasons that are selfish at the level of the genetic instructions, short-term altruism may be adaptive, and might be selected for—even if the members of the group are not near relatives. In closely knit communities, individual selection and what looks very much like group selection are both elicited.
Many examples thought to demonstrate group selection have, with an almost maddening ingenuity, been explained at least equally well by a new school of biologists and game theorists. Some explanations seem quite plausible, but not all. For example, when a predator threatens a group of Thomson gazelles, one or two may leap in conspicuous high arcs near the predator. This is called stotting. The group selectionist view is straightforward: The individual calls attention to itself and risks being eaten in order to save the group. (But suppose stotting were never invented; could the predator eat more than one Thomson gazelle anyway? Compared to other species of gazelles ignorant of stotting, are fewer eaten thanks to stotting?) The prevailing individual selectionist view is that the stotter is advertising its own gymnastic abilities and reminding the predator that less athletic gazelles are easier to eat. It stots for crassly selfish reasons.17 (But then why don’t most Thomson gazelles stot when stalked? Why doesn’t such selfishness spread through the herd? Does the predator in fact turn its attention from the stotter to a less conspicuous gazelle?)