The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature (45 page)

Apathy is nature's norm. Predators ignore all but a few favored species of prey. Parasites usually focus their attention on just one species of favored host. Darwin pointed out that most of the violent competition happens within a species, because animals of the same species are competing for the same resources and the same mates. Evolutionary biology focuses on competition because competition between genes drives evolution. Nevertheless, animals usually tend to avoid competition as much as possible. In particular, evolution almost never favors spite, which means hurting a competitor at a net cost to oneself. The costs of spite are carried entirely by oneself and one's victim, while the benefits of hurting that victim are enjoyed by all of one's other competitors.

Since apathy is the default attitude of any one animal to any other, we need not seek any special explanation for human apathy towards other humans or other animals. The hard things to explain are costly behaviors that help others, and costly behaviors that hurt others. If we were typical animals, our attitudes to others would be dominated not by hate, exploitation, spite, competitiveness, or treachery, but by indifference. And so they are. Immanuel Kant suggested that we view people either as ends in themselves or as means to our ends. Neutralism suggests that we usually view them as neither—neither subject nor object, just an occasion for a blank stare and a lazy shrug. What evolution has to explain about human morality is why we ever do anything other than shrug when we see opportunities for care and generosity.

The Hidden Benefits of Kindness

The evolution of morality did not have to get us over some ethical hump to move us from spiteful animal to generous human. We started in the middle, already sitting on the ethical fence, neutral and apathetic. We just needed some kind of selection pressure capable of favoring kindness. Any good evolutionary theory of human morality must convert the apparent costs of helping others into a realistic benefit to one's genes, by turning material costs into survival or reproductive benefits. If it cannot do that, it cannot explain how moral behaviors like kindness or generosity could evolve. The rules of evolutionary biology demand that we find a hidden, genetically selfish benefit to our altruism.

Some philosophers, theologians, and journalists are unhappy with this hidden-benefit requirement. They wish to define morality as purely selfless altruism, untainted by any hidden benefit. In their view, only the morality of the celibate saint qualifies as worthy of evolutionary explanation. But to my way of thinking, a moral theory of saints explains little about human nature, because saints are rare. Of the 15 billion or so humans who have lived since the time of Jesus Christ, the Catholic Church has canonized only a few thousand. Saints are literally one in a million. They may be instructive as moral ideals, but they

are statistically irrelevant as data about real human moral behavior. Moral philosophers are sometimes not clear about whether they are developing a descriptive explanation of human moral behavior as it is, or an ideal of saintly moral behavior as it should be. My interest here is in finding an evolutionary explanation of ordinary human kindness, not in accounting for the outer limits of saintly goodness.

One step down from theologians, but still high above the rest of us, sit the economists. They appear to explain human morality as they explain all behavior, in terms of rationally pursued preferences. If we are kind, we must have a taste for kindness, to which we attach some "subjective utility." If we give money to charity, that must be because the subjective utility we derive from giving exceeds the subjective utility that we would derive from holding on to the money. Most economists understand perfectly well that this "revealed preferences" principle is circular. It is a statement of the axioms that they use to prove theorems about the emergent effects of individual behavior in markets. It should not be confused with a psychological explanation of behavior, much less an evolutionary explanation.

Psychologists sometimes fail to understand how circular it is to "explain" moral behavior in terms of moral preferences. Of course, one can always say that we are kind because we choose to be kind, or it feels good to be kind, or we have brain circuits that reward us with endorphins when we are kind. Such responses beg the question of why those moral preferences, moral emotions, and moral brain circuits evolved to be standard parts of human nature. A costly behavior cannot evolve just because it happens to feel good. Feeling good must have evolved to motivate the behavior, which must have some hidden benefit.

Most evolutionary psychologists have agreed that kindness and generosity bring two major kinds of hidden benefit. One kind of benefit comes when the generosity is directed towards blood relatives. In such cases, the cost to one's own genes can be outweighed by benefits to copies of those genes in the bodies of relatives. This is the theory of kin selection, and it explains

generosity toward kin. The other kind of benefit comes when generosity is directed toward individuals who are likely to reciprocate in the future. Today's altruism may be repaid tomorrow. This is the theory of reciprocal altruism, which, it has been claimed, explains most instances of kindness to non-relatives.

Kinship and reciprocity are certainly important in human affairs, and we have evolved many psychological adaptations to deal with them. They go a long way in explaining many aspects of human moral behavior. For example, kinship theory puts into an evolutionary context the Confucian virtues of family obligation, while reciprocity helps to explain prudence, loyalty, guilt, and revenge. However, there is a lot left over. Human morality includes a great variety of behaviors and judgments that are hard to explain through kinship and reciprocity. Let's have a closer look at their limitations, and then see whether there are any other hidden evolutionary benefits to kindness.

Kinship

Kin selection theory was developed by W. D. Hamilton in 1964. It pointed out that there is a hidden genetic benefit in being kind to one's offspring and close genetic relatives. A gene for kindness to relatives can prosper because it tends to help other copies of the same gene to prosper, copies that happen to be in bodies other than one's own. They are there because they were passed down from the same recent common ancestor to both oneself and one's relatives. Thus, generosity to blood relatives is actually genetic selfishness.

This can be hard to understand, so let's view evolution from a selfish gene's point of view. Genes are "selfish" in the sense that they evolve to generate as many copies of themselves as possible. They act as if they are trying to spread throughout a population. Often, they do so by constructing bodies and brains that act as self-interested individuals. But that is by no means the only way for a selfish gene to spread. All genes would profit from being able to recognize and help copies of themselves in other bodies, and would be able to spread themselves better if they could. But most

of them cannot, because they help only to grow lungs, or livers, or some other blind organ incapable of generous behavior. Only a few kinds of genes have the power to be selectively generous to blood relatives. Some such genes are involved in growing a perceptual ability to distinguish kin from non-kin, or a behavioral ability to be kinder to kin. Others may grow nutrient-delivery systems such as wombs and breasts that nourish another individual that happens to be growing inside one's body, or clinging to oneself, which suggests they are probably one's own offspring. These are the main ways in which kindness-to-kin genes evolve.

Kin selection is really just a theory about how a particular kind of genetic mutation can spread. The only mutation that can assist other copies of itself in other bodies is a mutation for recognizing and favoring close genetic relatives. By favoring close relatives, who share a recent common ancestor, they are most likely to be favoring individuals who happen to carry a copy of this kin-favoring mutation. The whole edifice of family life, kinship, and parenting is based on a few very peculiar mutations that are directly responsible for kin recognition and nepotism. These kin recognition genes single-mindedly evolve better ways to recognize and assist one another, while all the other genes go about their business oblivious to kinship.

Kin selection predicts that we should be kinder to relatives who are more closely related to us: our altruism to kin should be in proportion to the likelihood of sharing the altruism gene with them. That likelihood is determined by how recently we shared a common ancestor, and how many common ancestors we shared. The likelihood of sharing the same kindness-to-kin gene is one half for siblings, parents, and offspring, but only a quarter for half-siblings, grandparents, grandchildren, nieces, nephews, aunts, and uncles. This is why we are usually kinder and closer to sisters than to nieces, even in societies where extended families live together.

A confusion commonly arises at this point. Kin selection theory is often misunderstood as saying we should be kind to other

organisms in proportion to the true percentage of genes we share with them. Don't all humans share about 99 percent of our DNA? That sounds close to identical twins, who share 100 percent of their DNA. If we share so many of our genes with other humans, why should we discriminate between close relatives and distant relatives? And don't we share about half of our genes with other mammals, birds and even fish? We should treat all herring as brothers and all sloths as sisters. We should apply the golden rule to all primates, be true friends to all mammals, allies to termites and tapeworms, and just slightly grudging compatriots of baobab trees, stinging nettles, and Antarctic lichens. Universal peace, cooperation, and symbiosis should reign on our blessed planet, according to this genetic-similarity interpretation of kinship.

It would be a weird and wonderful world if there were an evolutionary process that could favor altruism in proportion to true genetic similarity. Racism, ethnocentrism, xenophobia, sexism, human competition, crime, warfare, deforestation, pollution, and cruelty to animals would all vanish. We would all behave like Jainists—members of the Indian religion who dare not eat or move for fear of injuring another living being. But there is no such evolutionary process. Kinship theory offers only a forgetful, myopic, fumbling imitation, in which we have evolved the delusion that only our extremely close relatives have anything genetic in common with us.

How much of human morality derives from kin selection? Opinions vary. W. D. Hamilton, E. O. Wilson, and many others have suggested that adaptations for kindness to kin may have been important building blocks for kindness toward non-kin. Kin selection does not require a brain, but having a brain helps. It was a major step for brains to evolve the abilities to recognize individual relatives, determine how much care they should receive based on cues of genetic similarity, and produce care behaviors that actually benefit them. It looks as though it should be fairly easy to modify such adaptations to recognize individual non-relatives, determine how much care they should receive based on other kinds of cues, and produce effective care behaviors.

But would evolution favor such modifications? The genes underlying kindness to kin could have evolved only if they discriminated against non-kin. Their success ever since they originated as rare little mutations has depended on them being selectively altruistic, not generally altruistic. Although psychologically it looks like a small step to extend kin-based altruism to non-kin, it is a huge evolutionary leap that violates the basic rationale of kin selection. Being able to imagine "all men are brothers" is a long way from acting as though they are. Kin recognition is widespread among mammals. If human morality evolved as a free-and-easy side-effect of kin-based altruism, we might expect most mammals to show human-like morality They don't. Apparently, evolution ruthlessly eliminates all kinship genes that lose their discriminative abilities and start treating strangers as relatives. Kinship is powerful at explaining our kindness toward blood relatives, but it is hard to extend it beyond that.

Reciprocity

In the early 1970s, Robert Trivers pointed out that animals can benefit by being nice to one another if they interact often enough to build up trust. By keeping their promises and fulfilling their contracts, rather than opting for the short-term benefits of lying and cheating, they might obtain larger benefits over the longer term. Trivers's theory of "reciprocal altruism" suggested that many cases of apparent altruism are rationally selfish if viewed in their larger social context over the longer term. In reciprocity, there are three defining features: animals alternate giving and receiving benefits; each act has costs to the giver and benefits to the receiver; and giving is contingent on having received. As long as these three conditions hold, animals can trade benefits back and forth. Each act taken out of context may look altruistic, but the whole sequence is mutually beneficial. Trivers ingeniously showed how to connect the mathematics of reciprocity to the biology of altruism and the psychology of trust.

This logic of reciprocity was news to biologists, but not to economists. Trivers had rediscovered an economic principle

called the "folk theorem of repeated games." It is called a folk theorem because it was discovered independently by so many different game theorists in the early 1950s that none has ended up with individual credit. The theorem says that repeated interactions can be as powerful as contract law in maintaining cooperation. Any mutual benefits that two individuals could agree to provide to each other through a formal contract can also be sustained if the individuals interact sufficiently often. This is why traditional Chinese-style business that builds trust through repeated interaction can work as well as American-style business based on contracts and litigation.