Why Evolution Is True (38 page)

A COMMON BELIEF about evolution is that if we recognize that we are only evolved mammals, there will be nothing to prevent us from acting like beasts. Morality will be out the window, and the law of the jungle will prevail. This is the “naturalistic view of ethics” that Nancy Pearcey fears will pervade our schools. As the old Cole Porter song goes:

A more recent version of this notion was furnished by former congress-man Tom DeLay in 1999. Implying that the Columbine High School massacre in Colorado might have Darwinian roots, DeLay read out loud on the floor of the U.S. Congress a letter from a Texas newspaper suggesting—sarcastically—that “it [the massacre] couldn’t have been because our school systems teach the children that they are nothing but glorified apes who have evolutionized out of some primordial soup of mud.” In her best-selling book Godless: The
Church of Liberalism,
conservative pundit Ann Coulter is even more explicit, claiming that, for liberals, evolution “lets them off the hook morally. Do whatever you feel like doing—screw your secretary, kill Grandma, abort your defective child—Darwin says it will benefit humanity!” Darwin, of course, never said anything of the sort.

But does modern evolutionary biology even
claim
that we’re genetically hardwired to behave like our supposedly beastly forebears? To many, this impression came from the evolutionist Richard Dawkins’s immensely popular book The Selfish
Gene—
or rather from its title. This seemed to imply that evolution makes us behave selfishly, caring only for ourselves. Who wants to live in a world like that? But the book says nothing of the kind. As Dawkins shows clearly, the “selfish” gene is a metaphor for how natural selection works. Genes act
as
if they’re selfish molecules: those that produce better adaptations act as if they’re elbowing out other genes in the battle for future existence. And, to be sure, selfish genes can produce selfish behaviors. But there is also a huge scientific literature on how evolution can favor genes that lead to cooperation, altruism, and even morality. Our forebears may not have been entirely beastly after all, and in any case, the jungle, with its variety of animals, many of which live in quite complex and cooperative societies, is not as lawless as the saying implies.

So if our evolution as social apes has left its imprint on our brains, what sorts of human behavior might be “hardwired”? Dawkins himself has said that
The Selfish Gene
could equally well have been called
The Cooperative
Gene. Are we hardwired to be selfish, cooperative, or both?

In recent years a new academic discipline has arisen that tries to answer this question, interpreting human behavior in the light of evolution.
Evolutionary psychology
traces its origin to E. O. Wilson’s book Sociobiology, a sweeping evolutionary synthesis of animal behavior that suggested, in its last chapter, that human behavior could also have evolutionary explanations. Much of evolutionary psychology seeks to explain modern human behaviors as adaptive results of natural selection acting on our ancestors. If we take the beginning of “civilization” at about 4000 BC, when there were complex societies both urban and agricultural, then only six thousand years have passed until now. This represents only one-thousandth of the total time that the human lineage has been isolated from that of chimpanzees. Like icing on a cake, roughly 250 generations of civilized society lie atop 300,000 generations during which we may have been hunter-gatherers living in small social groups. And selection would have had many eons to adapt us to such a life-style. Evolutionary psychologists call the physical and social environment to which we adapted during this long period the “Environment of Evolutionary Adaptedness,” or EEA.
⁵⁵
Surely, as evolutionary psychologists say, we must retain many behaviors that evolved in the EEA, even if they are no longer adaptive—or even maladaptive. After all, there’s been relatively little time for evolutionary change since the rise of modern civilization.

Indeed, all human societies seem to share a number of widely recognized “human universals.” Donald Brown listed dozens of such traits in his book by that name, including the use of symbolic language (in which words are abstract symbols for actions, objects, and thoughts), the division of labor between the sexes, male dominance, religious or supernatural belief, mourning for the dead, favoring relatives over nonrelatives, decorative art and fashion, dance and music, gossip, body adornment, and a love of sweets. Because most of these behaviors distinguish humans from other animals, they can be seen as aspects of “human nature.”

But we shouldn’t always assume that widespread behaviors reflect genetically based adaptations. One problem is that it is all too easy to make up an evolutionary reason why many modern human behaviors should have been adaptive in the EEA. For example, art and literature might be the equivalent to the peacock’s tail, with artists and writers leaving more genes because their productions appealed to women. Rape? It’s a way for men who can’t find mates to father offspring; such men were then selected in the EEA for a propensity to overpower and forcibly copulate with women. Depression ? No problem: it could be a way of withdrawing adaptively from stressful situations, mustering your mental resources so that you can cope with life. Or it could represent a ritualized form of social defeat, enabling you to withdraw from competition, recoup, and come back to struggle another day. Homosexuality? Even though this behavior seems the very opposite of what natural selection would foster (genes for gay behavior, which don’t get passed on, would quickly disappear from populations), one can save the day by assuming that, in the EEA, homosexual males stayed home and helped their mothers produce other offspring. In this circumstance, “gayness” genes could be passed on by homosexuals producing more brothers and sisters, individuals who share those genes. None of these explanations, by the way, are mine. All of them have actually appeared in the published scientific literature.

There is an increasing (and disturbing) tendency of psychologists, biologists, and philosophers to Darwinize every aspect of human behavior, turning its study into a scientific parlor game. But imaginative reconstructions of how things might have evolved are not science; they are stories. Stephen Jay Gould satirized them as “Just-So Stories,” after Kipling’s eponymous book that gave delightful but fanciful explanations for various traits of animals (“How the Leopard Got His Spots,” and so on).

Yet we can’t dismiss
all
behaviors as having no evolutionary basis. Surely some of them do. These include behaviors that are almost certainly adaptations because they’re widely shared among animals and whose importance in survival and reproduction is obvious. Behaviors that come to mind are eating, sleeping (though we don’t know yet why we need to sleep, a resting period of the brain is widespread in animals), a sex drive, parental care, and favoring relatives over nonrelatives.

A second category of behaviors includes those very likely to have evolved by selection, but whose adaptive significance is not quite as clear as, say, parental care. Sexual behavior is the most obvious. In parallel with many animals, human males are largely promiscuous and females choosy (this despite the socially enforced monogamy that prevails in many societies). Males are larger and stronger than females and have higher levels of testosterone, a hormone associated with aggression. In societies where reproductive success has been measured, its variation among males is invariably higher than among females. Statistical surveys of personal ads in newspapers-granted, not the most rigorous form of scientific investigation—have shown that while men search for younger women with bodies suited to childbearing, women prefer somewhat older males who have wealth, status, and a willingness to invest in their relationships. All of these features make sense in light of what we know about sexual selection in animals. While this doesn’t make us quite the equivalent of elephant seals, the parallels strongly imply that features of our body and behavior were molded by sexual selection.

But we must again take care when extrapolating from other animals. Men might be larger not because they compete for women, but because of the evolutionary outcome of a division of labor: in the EEA, men might have hunted while women, the childbearers, took care of children and foraged for food. (Note that this is still an evolutionary explanation, but one that involves natural rather than sexual selection.) And it takes some mental contortions to try to explain
every
facet of human sexuality by evolution. In modern Western societies, for example, women adorn themselves much more elaborately than males, wearing makeup, diverse and fancy dress, and so on. This is very different from most sexually selected animals like the birds of paradise, in which it is males who have evolved elaborate displays, body colors, and ornaments. And there is always a temptation to look at behavior in our immediate surroundings, in our society, and forget that behaviors are often variable over time and space. Being homosexual may not be the same thing in San Francisco today as it was in Athens twenty-five hundred years ago. Few behaviors are as absolute, or inflexible, as language or sleeping. Nevertheless, we can be fairly confident that some aspects of sexual behavior, the universal love of fats and sweets, and our tendency to lay on fat reserves are traits that were adaptive in our ancestors—but not necessarily today. And linguists like Noam Chomsky and Steven Pinker have argued convincingly that the use of symbolic language is likely a genetic adaptation, with aspects of syntax and grammar somehow coded in our brains.

Finally, there is the very large category of behaviors sometimes seen as adaptations, but about whose evolution we know virtually nothing. This includes many of the most interesting human universals, including moral codes, religion, and music. There is no end of theories (and books) about how such features may have evolved. Some modern thinkers have constructed elaborate scenarios about how our sense of morality, and many moral tenets, might be the products of natural selection working on the inherited mind-set of a social primate, just as language enabled the building of a complex society and culture. But in the end these ideas come down to untested—and probably untestable—speculations. It’s almost impossible to reconstruct how these features evolved (or even if they
are
evolved genetic traits) and whether they are direct adaptations or, like making fire, merely by-products of a complex brain that evolved behavioral flexibility to take care of its body. We should be deeply suspicious of speculations that come unaccompanied by hard evidence. My own view is that conclusions about the evolution of human behavior should be based on research at least as rigorous as that used in studying nonhuman animals. And if you read the animal-behavior journals, you’ll see that this requirement sets the bar pretty high, so that many assertions about evolutionary psychology sink without a trace.

There is no reason, then, to see ourselves as marionettes dancing on the strings of evolution. Yes, certain parts of our behavior may be genetically encoded, instilled by natural selection in our savanna-dwelling ancestors. But genes aren’t destiny. One lesson that all geneticists know, but which doesn’t seem to have permeated the consciousness of nonscientists, is that “genetic” does not mean “unchangeable.” All sorts of environmental factors can affect the expression of genes. Juvenile diabetes, for example, is a genetic disease, but its harmful effects can be largely eliminated by small doses of insulin: an environmental intervention. My poor eyesight, which runs in the family, is no encumbrance thanks to glasses. Likewise, we can curtail our voracious appetites for chocolate and meat with some willpower and the help of Weight Watchers meetings, and the institution of marriage has gone a long way toward curbing the promiscuous behavior of men.

The world still teems with selfishness, immorality, and injustice. But look elsewhere and you’ll also find innumerable acts of kindness and altruism. There may be elements of both behaviors that come from our evolutionary heritage, but these acts are largely matters of choice, not of genes. Giving to charity, volunteering to eradicate disease in poor countries, fighting fires at immense personal risk—none of these acts could have been instilled in us directly by evolution. And as the years pass, although horrors like “ethnic cleansing” in Rwanda and the Balkans are still with us, we see an increasing sense of justice sweeping through the world. In Roman times, some of the most sophisticated minds that ever existed found it an excellent afternoon’s entertainment to sit down and watch humans literally fighting for their lives against each other, or against wild animals. There is now no culture on the planet that would not think this barbaric. Similarly, human sacrifice was once an important part of many societies. That too has thankfully disappeared. In many countries, the equality of men and women is now taken for granted. Richer nations are becoming aware of their obligations to help, rather than exploit, poorer ones. We worry more about how we treat animals. None of this has anything to do with evolution, for the change is happening far too fast to be caused by our genes. It is clear, then, that whatever genetic heritage we have, it is not a straitjacket that traps us forever in the “beastly” ways of our forebears. Evolution tells us where we came from, not where we can go.

And although evolution operates in a purposeless, materialistic way, that doesn’t mean that our lives have no purpose. Whether through religious or secular thought, we make our own purposes, meaning, and morality. Many of us find meaning in our work, our families, and our avocations. There is solace, and food for the brain, in music, art, literature, and philosophy.

Many scientists have found profound spiritual satisfaction in contemplating the wonders of the universe and our ability to make sense of them. Albert Einstein, often mistakenly described as conventionally religious, nevertheless saw the study of nature as a spiritual experience: