The Moral Animal: Why We Are, the Way We Are: The New Science of Evolutionary Psychology (58 page)

In this view, the fact that some people's sexual impulses get diverted from typical channels is just another tribute to the malleability of the human mind. Given a particular set of environmental influences, it may do any number of things. (Prison is an extreme example of such an environmental influence; when heterosexual gratification is impossible, the sexual urge — especially the relatively strong and indiscriminate male sexual urge — may seek the closest substitute.)

Is there a "gene" for homosexuality? There is evidence suggesting that some genes are more likely to lead to homosexuality than others. But that doesn't mean there's a "gay gene" — a gene that drives one inexorably to homosexuality, regardless of environment; and it certainly doesn't mean that the genes in question were selected by natural selection by virtue of their contribution to homosexuality. (Some genes no doubt make a person more likely to enter, say, banking, or professional football, than other genes; but there's no "banker gene" or "pro football gene" — no gene that was selected by virtue of its contribution to one's banking or football playing. Just genes conducive to, say, facility with numbers, or to physical strength.) Indeed, once you rule out the kin-selection theory of homosexual inclination, it is very hard to imagine a gene being selected by virtue of its leading to exclusive homosexuality. If there is a "gay gene" that has spread to a sizable part of the population, it probably was having some effect other than homosexual inclination in the environment in which it spread.

One reason some people are so concerned about the "gay gene" question is that they want to know if homosexuality is "natural," a question that — to them, at least — seems to have moral consequence. They think it matters greatly whether (a) there is a gene (or combination of
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genes) conducive to homosexuality that indeed was selected by virtue of that effect; or (b) there is a gene (or combination of genes) conducive to homosexuality that was selected for some other reason but, in some environments, has the effect of encouraging homosexuality; or (c) there is a gene (or combination of genes) con ducive to homosexuality that is a fairly recent arrival on the human scene and hasn't yet gotten a strong endorsement from natural selection for any particular property; or (d) there is no "gay gene."

But who cares? Why should the "naturalness" of homosexuality in any way affect our moral judgment of it? It is "natural," in the sense of being "approved" by natural selection, for a man to kill someone he finds sleeping with his wife. Rape may, in the same sense, be "natural." And seeing that your children are fed and clothed is surely "natural." But most people rightly judge these things by their consequences, not their origins. What is plainly true about homo sexuality is the following: (1) some people are born with a combi nation of genetic and environmental circumstance that impels them strongly toward a homosexual lifestyle; (2) there is no inherent con tradiction between homosexuality among consenting adults and the welfare of other people. For moral purposes (I believe) that should be the end of the discussion.

2. Why are siblings so different from one another?
If genes are so important, why do people who have so many genes in common so often turn out so unlike one another? In a certain sense, this question isn't a logical one to ask an evolutionary psychologist. After all, mainstream evolutionary psychology doesn't study how different genes lead to different behaviors, but how the genes common to tin-human species can lead to various behaviors — sometimes different, sometimes similar. In other words, evolutionary psychologists typically analyze behavior without regard to an individual's peculiar genetic constitution. Still, the answer to this question about siblings sheds much light on a puzzle that is central to evolutionary psychology: If the main genetic influences on human behavior come from genes that all people share, why do people in general behave so differently from one another? We've addressed this question from various angles in this book, but the matter of siblings sheds a new kind of light on it.
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Consider Darwin. He was the second youngest of six children. As such, he conforms to a striking pattern that has only recently come to light: people who initiate or support scientific revolutions are exceedingly unlikely to be firstborn children. Frank Sulloway (see Sulloway [in press]), who has documented this pattern with voluminous data, has also found that people who lead or support political revolutions are very unlikely to be firstborn children.

How to explain this pattern? Presumably, Sulloway notes, it has something to do with the fact that younger children often find themselves in competition with older siblings — authority figures — for resources. Indeed, they may find themselves in conflict not just with these particular authorities, but with a whole establishment. After all, firstborn children, having higher reproductive value than their younger siblings (see chapter seven), should, in theory, tend to be favored by parents, all other things being equal. So there may often be a natural commonality of interest, an alliance, between parents and older siblings that younger siblings find themselves combatting. the establishment lays down the law, the younger sibling challenges it. It could be adaptive for children who find themselves thus situated to become good at questioning received rules. That is: a species-typical developmental program may tend to steer children with older siblings toward radical thought.

The larger point here is about "nonshared environment," whose importance geneticists have grasped only over the last decade (see Plomin in and Daniels [1987]). People who doubt environmental determinism like to point to two brothers, raised side-by-side, and ask why one of them became, say, a criminal and the other a district attorney. If environment is so important, they ask, why did these people turn out so differently? Such questions misconstrue the meaning of "environment." Though two brothers do share some aspects of their environment (the same parents, same school) a large part of their environment is "nonshared" (who their first-grade teacher was, who their friends are, and so on).

Paradoxically, as Sulloway (see Sulloway [in preparation]) points out, siblings may, by virtue of being siblings, have particularly disparate "nonshared" environments. For example, while you and your
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next-door neighbor may both be firstborn children — and thus "share" this environmental influence — the same can't possibly be true of both you and your sibling. What's more: Sulloway believes that one sibling, by virtue of occupying a certain strategic "niche" within the family ecology, may push other siblings toward other niches in their struggle to compete for resources. Thus, a younger sibling may find that another sibling has already won great favor through, say, conscientious sacrifice for the parents; in response, he or she may seek another "niche" — excellence in school, say — rather than try to compete in the already crowded sacrifice market.

3. Why do people choose to have few or no kids?
This is sometimes cited as a great evolutionary "mystery." Academics have puzzled over the "demographic transition" that lowered birthrates in indus trialized societies, trying to explain it in Darwinian terms. Some theorize, for example, that in a modern environment, having what was once considered an average-sized family can be bad for your genetic legacy. Maybe you will wind up with more grandchildren if you have two children, both of whom you can afford to educate at expensive private schools, than if you have five children who get educated at cheaper schools and find themselves unable to support children themselves. Thus, in having fewer children, people are be having adaptively.

There is a simpler solution: natural selection's primary means of getting us to reproduce hasn't been to instill in us an overwhelming, conscious desire to have children. We are designed to love sex and then to love the consequences that materialize nine months later — not necessarily to anticipate loving the consequences. (Witness the Trobriand Islanders, who according to Malinowski hadn't grasped the connection between sex and childbirth but, nonetheless, had man aged to keep reproducing.) Only in the wake of contraceptive tech nology has this design faltered.

The choice of family size is one of many cases where we have outsmarted natural selection; through conscious reflection — seeing, for example, that children, however lovable, can be quite burdensome in certain quantities — we can choose to short-circuit the ultimate goals that natural selection "intended" us to pursue.
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4. Why do people commit suicide?
Again, one can try to construct scenarios in which this sort of behavior might be adaptive. Maybe a person in the ancestral environment who had become a burden on his family would actually maximize inclusive fitness by taking himself out of the picture. Maybe, for example, food is so scarce that by continuing to eat he would deprive more reproductively valuable relatives of nutrients to the point of endangering their lives.

This explanation is not entirely implausible, but there are some problems with it. One is that, in the modern environment at least, people who commit suicide seldom belong to families near starvation.

And, really, being near starvation is just about the only circumstance in which suicide could make much Darwinian sense. Given fairly abundant available food, almost anyone — except the seriously handicapped, or the extremely old and infirm — could, by staying alive, contribute substantially to their reproductively valuable relatives: gather berries, tend children, teach children, etcetera. (And, anyway, even if you have become an unjustifiable burden on your family, would out-and-out suicide be the genetically optimal path? Wouldn't it be better for, say, a depressed man's genes if he just wandered away from the village, hoping to find better luck elsewhere — hoping, perhaps, to encounter some strange woman he can try to seduce, if not rape?)

A likely resolution of the suicide paradox lies in remembering that the behavioral "adaptations" designed by natural selection aren't the behaviors per se but the underlying mental organs. And mental organs that were adaptive enough, in one environment, to become part of human nature may, in another environment, lead to behaviors that are maladaptive. We've seen, for example, why feeling bad about yourself may sometimes be adaptive (chapter thirteen). But, alas, the mental organ designed to make you feel bad about yourself can misfire; feeling bad about yourself for too long, without relief, may lead to suicide.

Modern environments seem more likely than some previous environments to lead to this sort of malfunctioning. They permit, for example, a degree of social isolation that was unknown to our ancestors.
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5. Why do people kill their own children?
Infanticide is no mere product of a modern environment. It has happened abundantly in hunter-gatherer cultures and agrarian cultures. Is it, then, the result of an adaptation — a mental organ that implicitly calculates when killing a newborn will maximize genetic fitness? Quite possibly. Not only are unhealthy and handicapped babies more likely to be killed; so are babies born under various other kinds of inauspicious circumstances — when, say, the mother already has young children and has no husband.

Of course, in the modern environment, it is harder to explain thr killing of offspring as a sound genetic stratagem. But as we've seen (chapter four), many cases of supposed offspring murder are in fact the murder of a stepoffspring. Many of the rest, I suspect, are committed by husbands who may in fact be the natural father but have begun to doubt — consciously or unconsciously — that they are. And in those relatively few cases where a mother kills her own newborn baby, it is often amid the sort of environmental cues that, in the ancestral environment, might have meant that infanticide would be genetically profitable: relative poverty, no reliable source of male parental investment, etcetera.

6. Why do soldiers die for their country?
Jumping on a hand grenade — or, in the ancestral environment, suicidally leading a defense against club-wielding invaders — may make Darwinian sense if you're in the presence of close relatives. But why die for a bunch of people who are just friends? That's one favor you'll never have the pleasure of seeing repaid.

First, it is worth remembering that in the ancestral environment, in a small hunter-gatherer village, the average degree of kinship to a comrade in arms was not negligibly low — and, indeed, depending on patterns of marriage, could be fairly high (see Chagnon [1988]). In discussing the theory of kin selection in chapter seven, we focused on mental organs that identify close kin and treat them with special generosity; and, we suggested, genes conducive to such discrimination will tend to flourish at the expense of genes that bestow altruism more diffusely. But there may be a few circumstances that don't
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permit such fine discernment. One such circumstance is a collective threat. If, say, a whole hunter-gatherer band, including your immediate family and many near relatives, is under dire attack, inordinate bravery could make straightforward genetic sense by virtue of kin selection. Men in modern war may sometimes act under the influence of a tendency to bestow just such indiscriminate altruism in warlike situations. A nother difference between modern war and ancestral war is that the genetic payoff of victory is now lower. It is reasonable to suspect — based on observation of preliterate societies — that the rape or abduction of women was once a common feature of war. Thus the rewards were large enough, in Darwinian terms, to justify substantial risk (though not plainly suicidal behavior). And it is likely that the men who demonstrated the most valor during war were rewarded most richly. In sum, the best guess about valor in wartime is that it is the product of mental organs that once served to maximize inclusive fitness and may no longer do so. But the organs persist, ready to be exploited by, among others, political leaders who profit from war (see Johnson [1987]).

Human behavior poses many other Darwinian mysteries. What are the unctions of humor and laughter? Why do people make deathbed confessions? Why do people take vows of poverty and chastity — and even, occasionally, keep them? What is the exact function of grief? (Surely it signifies, as we assumed in chapter seven, the degree of emotional investment in the deceased, and surely the emotional investment itself made genetic sense while the person was alive. But now that the person is gone, how does grieving serve the genes?)