The Moral Animal: Why We Are, the Way We Are: The New Science of Evolutionary Psychology (14 page)

Of course, one could argue that various policy implications ensue from any given theory. And one can dream up wholly different kinds of Darwinian theories about how sexual strategies get shaped.
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The one thing one can't do, I submit, is argue that evolutionary psychology is irrelevant to the whole discussion. The idea that natural selection, acutely attentive to the most subtle elements of design in the lowliest animals, should build huge, exquisitely pliable brains and not make them highly sensitive to environmental cues regarding sex, status, and various other things known to figure centrally in our reproductive prospects — that idea is literally incredible. If we want to know when and how a person's character begins to assume distinct shape, if we want to know how resistant to change the character will subsequently be, we have to look to Darwin. We don't yet know the answers, but we know where they'll come from, and that knowledge helps us phrase the questions more sharply.

Much of the attention paid to the "short-term" sexual strategies of women — whether unattached women willing to settle for a one-night stand, or attached women sneaking out on a mate — is fairly recent. Sociobiological discussion during the 1970s, at least in its popular form, tended to depict men as wild, libidinous creatures who roamed the landscape looking for women to dupe and exploit; women were often depicted as dupes and exploitees. The shift in focus is due largely to the growing number of female Darwinian social scientists, who have patiently explained to their male colleagues how a woman's psyche looks from the inside.

Even after this restoration of balance, there remains one important sense in which men and women will tend to be, respectively, exploiter
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and exploited. As a marriage progresses, the temptation to desert should — in the average case — shift toward the man. The reason isn't, as people sometimes assume, that the Darwinian costs of marital breakup are greater for the woman. True, if she has a young child and her marriage dissolves, that child may suffer — whether because she can't find a husband willing to commit to a woman with another man's child, or because she finds one who neglects or mistreats the child. But, in Darwinian terms, this cost is borne equally by the deserting husband; the child who will thus suffer is his child too, after all.

The big difference between men and women comes, rather, on the benefits side of the desertion ledger. What can each partner gain from a breakup in the way of future reproductive payoff? The husband can, in principle, find an eighteen-year-old woman with twenty-five years of reproduction ahead. The wife — even aside from the trouble she'll have finding a husband if she already has a child — cannot possibly find a mate who will give her twenty-five years worth of reproductive potential. This difference in outside opportunity is negligible at first, when both husband and wife are young. But as they age, it grows.

Circumstance can subdue or heighten it. A poor, low-status husband may not have a chance to desert and may, indeed, provide his wife with reason to desert, especially if she has no children and can thus find another mate readily. A husband who rises in status and wealth, on the other hand, will thus strengthen his incentive to desert while weakening his wife's. But all other things being equal, it is the husband's restlessness that will tend to grow as the years pass.

All this talk of "desertion" may be misleading. Though divorce is available in many hunter-gatherer cultures, so is polygyny; in the ancestral environment, gaining a second wife didn't necessarily mean leaving the first. And so long as it didn't, there was no good Darwinian reason to desert. Staying near offspring, giving protection and guidance, would have made more genetic sense. Thus, males may be designed less for opportune desertion than for opportune polygyny. But in the modern environment, with institutionalized monogamy, a polygynous impulse will find other outlets, such as divorce.

As a mother's children grow self-sufficient, the urgency of hanging
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onto male parental investment drops. There are plenty of middle-aged women who, especially if they're financially secure, can take or leave their husbands. Still, there is no Darwinian force driving them to leave their husbands, nothing about leaving him that will sharply advance their genetic interests. The thing most likely to drive a post-menopausal woman out of a marriage is her husband's malicious marital discontent. Many a woman seeks divorce, but that doesn't mean her genes are ultimately the problem.

Among all the data on contemporary marriage, two items stand out as especially telling. First is the 1992 study which found that the husband's dissatisfaction with a marriage is the single strongest predictor of divorce.
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Second is that men are much more likely than women to remarry after a divorce.
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The second fact — and the biological force behind the second fact — is probably a good part of the reason for the first.

Objections to this sort of analysis are predictable: "But people leave marriages for emotional reasons. They don't add up the number of their children and pull out their calculators. Men are driven away by dull, nagging wives, or by the profound soul-searching of a mid-life crisis. Women are driven out by abusive or indifferent husbands, or lured away by a sensitive, caring man."

All true. But, again: emotions are just evolution's executioners. Beneath all the thoughts and feelings and temperamental differences that marriage counselors spend their time sensitively assessing are the stratagems of the genes — cold, hard equations composed of simple variables: social status, age of spouse, number of children, their ages, outside opportunities, and so on. Is the wife really duller and more nagging than she was twenty years ago? Possibly, but it's also possible that the husband's tolerance for nagging has dropped now that she's forty-five and has no reproductive future. And the promotion he just got, which has already drawn some admiring glances from a young woman at work, hasn't helped. Similarly, we might ask the young childless wife who finds her husband intolerably insensitive why the insensitivity wasn't so oppressive a year ago, before he lost his job and she met the kindly, affluent bachelor who seems to be flirting with her. Of course, maybe her husband's abuses are quite real, in which case they signal his disaffection, and perhaps his impending
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departure — and merit just the sort of preemptive strike the wife is now mustering.

Once you start seeing everyday feelings and thoughts as genetic weapons, marital spats take on new meaning. Even the ones that aren't momentous enough to bring divorce are seen as incremental renegotiations of contract. The husband who on his honeymoon said he didn't want an "old-fashioned wife" now sarcastically suggests that it wouldn't be too taxing for her to cook dinner once in a while. The threat is as clear as it is implicit: I'm willing and able to break the contract if you're not willing to renegotiate.

All told, things are not looking good for Desmond Morris's version of the pair-bond hypothesis. We do not seem to be too much like our famously, just about unswervingly, monogamous primate relatives, the gibbons, to which we have been optimistically compared. This should come as no great surprise. Gibbons aren't very social. Each family lives on a large home range — sometimes more than a hundred acres — that buffers it from extramarital dalliances. And gibbons chase off any intruders that might want to steal or borrow a mate.
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We, by contrast, have evolved in large social groups that are rife with genetically profitable alternatives to fidelity.

We do have, to be sure, the earmarks of high male parental investment. For hundreds of thousands of years, and maybe longer, natural selection has been inclining males to love their children, thus giving them a feeling females had been enjoying for the previous several hundred million years of mammalian evolution. Natural selection has also, during that time, been inclining men and women to love each other (or, at least, to "love" each other, with the meaning of that word varying greatly, and seldom approaching the constancy of devotion it reaches between parent and offspring). Still, love or no love, gibbons we aren't.

So what are we? Just how far from being naturally monogamous is our species? Biologists often answer this question anatomically. We've already seen anatomical evidence — testes weight and the fluctuations in sperm density — suggesting that human females are not devoutly monogamous by nature. There is also anatomical evidence
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bearing on the question of precisely how far from monogamous males naturally are. As Darwin noted, in highly polygynous species the contrast in body size between male and female — the "sexual dimorphism" — is great. Some males monopolize several females, while other males get shut out of the genetic sweepstakes altogether, so there is immense evolutionary value in being a big male, capable of intimidating other males. Male gorillas, who mate with lots of females if they win lots of fights and no females if they win none, are gargantuan — twice as heavy as females. Among the monogamous gibbons, small males breed about as prolifically as bigger ones, and sexual dimorphism is almost imperceptible. The upshot is that sexual dimorphism is a good index of the intensity of sexual selection among males, which in turn reflects how polygynous a species is. When placed on the spectrum of sexual dimorphism, humans get a "mildly polygynous" rating.
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We're much less dimorphic than gorillas, a bit less than chimps, and markedly more than gibbons.

One problem with this logic is that competition among human, and even prehuman, males has been largely mental. Men don't have the long canine teeth that male chimps use to fight for alpha rank and thus supreme mating rights. But men do employ various stratagems to raise their social status, and thus their attractiveness. So some, and maybe much, of the polygyny in our evolutionary past would be reflected not in gross physiology but in distinctively male mental traits. If anything, the less than dramatic difference in size between men and women paints an overly flattering picture of men's monogamous tendencies.
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How have societies over the years coped with the basic sexual asymmetry in human nature? Asymmetrically. A huge majority — 980 of the 1,154 past or present societies for which anthropologists have data — have permitted a man to have more than one wife.
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And that number includes most of the world's hunter-gatherer societies, societies that are the closest thing we have to a living example of the context of human evolution.

The more zealous champions of the pair-bond thesis have been known to minimize this fact. Desmond Morris, hell-bent on proving the natural monogamy of our species, insisted in
The Naked Ape
that the only societies worth paying much attention to are modern
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industrial societies, which, coincidentally, fall into the 15 percent of societies that have been avowedly monogamous. "[A]ny society that has failed to advance has in some sense failed, 'gone wrong,' " he wrote. "Something has happened to it to hold it back, something that is working against the natural tendencies of the species. ..." So "the small, backward, and unsuccessful societies can largely be ignored." In sum, said Morris (who was writing back when Western divorce rates were about half what they are now): "whatever obscure, backward tribal units are doing today, the mainstream of our species expresses its pair-bonding character in its most extreme form, namely long-term monogamous matings."
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Well, that's one way to get rid of unsightly, inconvenient data: declare them aberrant, even though they vastly outnumber the "mainstream" data.

Actually, there is a sense in which polygynous marriage has not been the historical norm. For 43 percent of the 980 polygynous cultures, polygyny is classified as "occasional." And even where it is "common," multiple wives are generally reserved for a relatively few men who can afford them or qualify for them via formal rank. For eons and eons, most marriages have been monogamous, even though most societies haven't been.

Still, the anthropological record suggests that polygyny is natural in the sense that men given the opportunity to have more than one wife are strongly inclined to seize it. The record also suggests something else: that polygyny has its virtues as a way of handling the basic imbalance between what men and women want. In our culture, when a man whose wife has given him a few children grows restless and "falls in love" with a younger woman, we say: Okay, you can marry her, but we insist that you desert your first wife and that a stigma be placed on your kids and that, if you don't make much money, your kids and former wife suffer miserably. Some other cultures have tended to say: Okay, you can marry her, but only if you can really afford a second family; and you can't desert your first family, and there won't be any stigma placed on your kids.

Maybe some of today's nominally monogamous societies, those in which half of all marriages actually fail, should just go whole hog. Maybe we should fully erase the already fading stigma of divorce.
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Maybe we should simply make sure that men who stray from their families remain legally responsible for them, and keep supporting them in the manner to which they had become accustomed. Maybe we should, in short, permit polygyny. A lot of presently divorced women, and their children, might be better off.

The only way to intelligently address this option is to first ask a simple question (one that turns out to have a counterintuitive answer): How did a strict cultural insistence on monogamy, which seems to go against the grain of human nature, and several millennia ago was almost unheard of, ever come to be?
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