WHAT DO WOMEN WANT?
For a species low in male parental investment, the basic dynamic of courtship, as we've seen, is pretty simple: the male really wants sex; the female isn't so sure. She may want time to (unconsciously) assess the quality of his genes, whether by inspecting him or by letting him battle with other males for her favor. She may also pause to weigh the chances that he carries disease. And she may try to extract a precopulation gift, taking advantage of the high demand for her eggs. This "nuptial offering"—which technically constitutes a tiny male parental investment, since it nourishes her and her eggs—is seen in a variety of species, ranging from primates to black-tipped hanging flies. (The female hanging fly insists on having a dead insect to eat during sex. If she finishes it before the male is finished, she may head off in search of another meal, leaving him high and dry. If she isn't so quick, the male may repossess the leftovers for subsequent dates.) These various female concerns can usually be addressed fairly quickly; there's no reason for courtship to drag on for weeks.
But now throw high MPI into the equation—male investment not just at the time of sex, but extending up to and well beyond birth. Suddenly the female is concerned not only with the male's genetic investment, or with a free meal, but with what he'll bring to the offspring after it materializes. In 1989 the evolutionary psychologist David Buss published a pioneering study of mate preferences in thirty-seven cultures around the world. He found that
in every culture, females placed more emphasis than males on a potential mate's financial prospects.
That doesn't mean women have a specific, evolved preference for
wealthy men. Most hunter-gatherer societies have very little in the way of accumulated resources and private property. Whether this accurately reflects the ancestral environment is controversial; hunter-gatherers have, over the last few millennia, been shoved off of rich land into marginal habitats and thus may not, in this respect, be representative of our ancestors. But if indeed all men in the ancestral environment were about equally affluent (that is, not very), women may be innately attuned not so much to a man's wealth as to his social status; among hunter-gatherers, status often translates into power—influence over the divvying up of resources, such as meat after a big kill. In modern societies, in any event, wealth, status, and power often go hand in hand, and seem to make an attractive package in the eyes of the average woman.
Ambition and industry also seem to strike many women as auspicious—and Buss found that this pattern, too, is broadly international. Of course, ambition and industriousness are things a female might look for even in a low-MPI species, as indices of genetic quality. Not so, however, for her assessment of the male's
willingness to invest.
A female in a high-MPI species may seek signs of generosity, trustworthiness, and, especially, an enduring commitment to her in particular. It is a truism that flowers and other tokens of affection are more prized by women than by men.
Why should women be so suspicious of men? After all, aren't males in a high-MPI species designed to settle down, buy a house, and mow the lawn every weekend? Here arises the first problem with terms like
love and
pair bonding. Males in high-MPI species are, paradoxically, capable of greater treachery than males in low-MPI species. For the "optimal male course," as Trivers noted, is a "mixed strategy." Even if long-term investment is their main aim, seduction and abandonment can make genetic sense, provided it doesn't take too much, in time and other resources, from the offspring in which the male does invest. The bastard youngsters may thrive even without paternal investment; they may, for that matter, attract investment from some poor sap who is under the impression that they're his. So
males in a high-MPI species should, in theory, be ever alert for opportunistic sex.
Of course, so should males in a low-MPI species. But this doesn't amount to exploitation, since the female has no chance of getting much more from another male. In a high-MPI species, she does, and a failure to get it from any male can be quite costly.
The result of these conflicting aims—the female aversion to exploitation, the male affinity for exploiting—is an evolutionary arms race. Natural selection may favor males that are good at deceiving females about their future devotion and favor females that are good at spotting deception; and the better one side gets, the better the other side gets.
It's a vicious spiral of treachery and wariness—even if, in a sufficiently subtle species, it may assume the form of soft kisses, murmured endearments, and ingenuous demurrals.
At least it's a vicious spiral
in theory. Moving beyond all this theoretical speculation and into the realm of concrete evidence— actually glimpsing the seamy underside of kisses and endearments—is tricky. Evolutionary psychologists have made only meager progress. True, one study found that males, markedly more than females, report depicting themselves as more kind, sincere, and trustworthy than they actually are. But that sort of false advertising may be only half the story, and the other half is much harder to get at. As Trivers didn't note in his 1972 paper, but did note four years later,
one effective way to deceive someone is to believe what you're saying. In this context, that means being blinded by love—to feel deep affection for a woman who, after a few months of sex, may grow markedly less adorable. This, indeed, is the great moral escape hatch for men who persist in a pattern of elaborate seduction and crisp, if anguished, abandonment. "I loved her at the time," they can movingly recall, if pressed on the matter.
This isn't to say that a man's affections are chronically delusional, that every swoon is tactical self-deception. Sometimes men
do make good on their vows of eternal devotion. Besides, in one sense, an out-and-out lie is impossible. There's no way of knowing in mid-swoon, either at the conscious or unconscious level, what the future holds. Maybe some more genetically auspicious mate will show up three years from now; then again, maybe the man will suffer some grave misfortune that renders him unmarketable, turning his spouse into his only reproductive hope. But, in the face of uncertainty as to how much commitment lies ahead, natural selection would likely err on the side of exaggeration, so long as it makes sex more likely and doesn't bring counterbalancing costs.
There probably would have been
some such costs in the intimate social environment of our evolution. Leaving town, or at least village, wasn't a simple matter back then, so blatantly false promises might quickly catch up with a man—in the form of lowered credibility or even shortened life span; the anthropological archives contain stories about men who take vengeance on behalf of a betrayed sister or daughter.
Also,
the supply of potentially betrayable women wasn't nearly what it is in the modern world. As Donald Symons has noted, in the average hunter-gatherer society, every man who can snare a wife does, and virtually every woman is married by the time she's fertile. There probably was no thriving singles scene in the ancestral environment, except one involving adolescent girls during the fruitless phase between first menstruation and fertility. Symons believes that
the lifestyle of the modern philandering bachelor—seducing and abandoning available women year after year after year, without making any of them targets for ongoing investment—is not a distinct, evolved sexual strategy. It is just what happens when you take the male mind, with its preference for varied sex partners, and put it in a big city replete with contraceptive technology.
Still, even if the ancestral environment wasn't full of single women sitting alone after one-night stands muttering "Men are scum," there were reasons to guard against males who exaggerate commitment. Divorce can happen in hunter-gatherer societies; men do up and leave after fathering a child or two, and may even move to another village. And polygamy is often an option. A man may vow that his bride will stay at the center of his life, and then, once married, spend half his time trying to woo another wife—or, worse still, succeed, and divert resources away from his first wife's children. Given such prospects,
a woman's genes would be well served by her early and careful scrutiny of a man's likely devotion. In any event, the gauging of a man's commitment does seem to be part of human female psychology; and male psychology does seem inclined to sometimes encourage a false reading.
That male commitment is in limited supply—that each man has only so much time and energy to invest in offspring—is one reason females in our species defy stereotypes prevalent elsewhere in the animal kingdom.
Females in low-MPl species—that is, in most sexual species—have no great rivalry with one another. Even if dozens of them have their hearts set on a single, genetically optimal male, he can, and gladly will, fulfill their dreams; copulation doesn't take long. But
in a high-MPI species such as ours, where a female's ideal is to monopolize her dream mate—steer his social and material resources toward her offspring—competition with other females is inevitable. In other words: high male parental investment makes sexual selection work in two directions at once.
Not only have males evolved to compete for scarce female eggs; females have evolved to compete for scarce male investment.
Sexual selection, to be sure, seems to have been more intense among men than among women. And it has favored different sorts of traits in the two. After all, the things women do to gain investment from men are different from the things men do to gain sexual access to women. (Women aren't—to take the most obvious example— designed for physical combat with each other, as men are.) The point is simply that,
whatever each sex must do to get what it wants from the other, both sexes should be inclined to do it with zest. Females in a high-MPI species will hardly be passive and guileless. And they will sometimes be the natural enemies of one another.
WHAT DO MEN WANT?
It would be misleading to say that males in a high-male-parental-investment species are selective about mates, but in theory they are at least
selectively selective. They will, on the one hand, have sex with just about anything that moves, given an easy chance, like males in a low-MPI species. On the other hand,
when it comes to finding a female for a long-term joint venture, discretion makes sense; males can undertake only so many ventures over a lifetime, so the genes that the partner brings to the project—genes for robustness, brains, whatever—are worth scrutinizing.
The distinction was nicely drawn by a study in which
both men and women were asked about the minimal level of intelligence they would accept in a person they were "dating." The average response, for both male and female, was: average intelligence. They were also asked how smart a person would have to be before they would consent to sexual relations. The women said: Oh, in that case, markedly above average. The men said: Oh, in that case, markedly below average.
Otherwise, the responses of male and female moved in lockstep. A partner they were "steadily dating" would have to be much smarter than average, and a marriageable partner would have to be smarter still. This finding, published in 1990, confirmed a prediction Trivers had made in his 1972 paper on parental investment.
In a high-MPI species, he wrote, "a male would be selected to differentiate between a female he will only impregnate and a female with whom he will also raise young. Toward the former he should be more eager for sex and less discriminating in choice of sex partner than the female toward him, but toward the latter he should be about as discriminating as she toward him."
As Trivers knew, the nature of the discrimination, if not its intensity, should still differ between male and female. Though both seek general genetic quality, tastes may in other ways diverge.
Just as women have special reason to focus on a man's ability to provide resources, men have special reason to focus on the ability to produce babies. That means, among other things, caring greatly about the age of a potential mate, since fertility declines until menopause, when it falls off abruptly. The last thing evolutionary psychologists would expect to find is that a plainly postmenopausal woman is sexually attractive to the average man. They don't find it. (According to Bron-islaw Malinowski, Trobriand Islanders considered sex with an old woman "indecorous, ludicrous, and unaesthetic.") Even before menopause, age matters, especially in a long-term mate; the younger a woman, the more children she can bear
. In every one of Buss's thirty-seven cultures, males preferred younger mates (and females preferred older mates).
The importance of youth in a female mate may help explain the extreme male concern with physical attractiveness in a spouse (a concern that Buss also documented in all thirty-seven cultures).
The generic "beautiful woman"—yes, she has actually been assembled, in a study that collated the seemingly diverse tastes of different men— has large eyes and a small nose. Since her eyes will look smaller and her nose larger as she ages, these components of "beauty" are also marks of youth, and thus of fertility.
Women can afford to be more open-minded about looks; an oldish man, unlike an oldish woman, is probably fertile.
Another reason for the relative flexibility of females on the question of facial attractiveness may be that a woman has other things to (consciously or unconsciously) worry about. Such as: Will he provide for the kids?
When people see a beautiful woman with an ugly man, they typically assume he has lots of money or status. Researchers have actually gone to the trouble of showing that people make this inference, and that the inference is often correct.
When it comes to assessing character—to figuring out if you can
trust a mate—a male's discernment may again differ from a female's, because
the kind of treachery that threatens his genes is different from the kind that threatens hers. Whereas the woman's natural fear is the withdrawal of his investment, his natural fear is that the investment is misplaced. Not long for this world are the genes of a man who spends his time rearing children who aren't his. Trivers noted in 1972 that, in a species with high male parental investment and internal fertilization, "adaptations should evolve to help guarantee that the female's offspring are also his own."
All of this may sound highly theoretical—and of course it is. But this theory, unlike the theory about male love sometimes being finely crafted self-delusion, is readily tested. Years after Trivers suggested that anticuckoldry technology might be built into men, Martin Daly and Margo Wilson found some. They realized that if indeed a man's great Darwinian peril is cuckoldry, and a woman's is desertion, then male and female jealousy should differ.
Male jealousy should focus on sexual infidelity, and males should be quite unforgiving of it; a female, though she'll hardly applaud a partner's extracurricular activities, since they consume time and divert resources,
should be more concerned with emotional infidelity—the sort of magnetic commitment to another woman that could eventually lead to a much larger diversion of resources.
These predictions have been confirmed—by eons of folk wisdom and, over the past few decades, by considerable data. What drives men craziest is the thought of their mate in bed with another man; they don't dwell as much as women do on any attendant emotional attachment, or the possible loss of the mate's time and attention. Wives, for their part, do find the sheerly sexual infidelity of husbands traumatic, and do respond harshly to it, but the long-run effect is often a self-improvement campaign: lose weight, wear makeup, "win him back." Husbands tend to respond to infidelity with rage; and even after it subsides, they often have trouble contemplating a continued relationship with the infidel.
Looking back, Daly and Wilson saw that this basic pattern had been recorded (though not stressed) by psychologists before the theory of parental investment came along to explain it. But evolutionary psychologists have now confirmed the pattern in new and excruciating detail.
David Buss placed electrodes on men and women and had them envision their mates doing various disturbing things. When men imagined sexual infidelity, their heart rates took leaps of a magnitude typically induced by three successive cups of coffee. They sweated. Their brows wrinkled. When they imagined instead a budding emotional attachment, they calmed down, though not quite to their normal level. For women, things were reversed: envisioning emotional infidelity—redirected love, not supplementary sex—brought the deeper physiological distress.
The logic behind male jealousy isn't what it used to be. These days some adulterous women use contraception and thus don't, in fact, dupe their husbands into spending two decades shepherding another man's genes. But the weakening of the logic doesn't seem to have weakened the jealousy. For the average husband, the fact that his wife inserted a diaphragm before copulating with her tennis instructor will not be a major source of consolation.
The classic example of an adaptation that has outlived its logic is the sweet tooth. Our fondness for sweetness was designed for an environment in which fruit existed but candy didn't. Now that a sweet tooth can bring obesity, people try to control their cravings, and sometimes they succeed. But their methods are usually roundabout, and few people find them easy; the basic sense that sweetness feels good is almost unalterable (except by, say, repeatedly pairing a sweet taste with a painful shock). Similarly, the basic impulse toward jealousy is very hard to erase. Still, people can muster some control over the impulse, and, moreover, can muster much control over some forms of its expression, such as violence, given a sufficiently powerful reason. Prison, for example.
WHAT ELSE DO WOMEN WANT?
Before further exploring the grave imprint that cuckoldry has left on the male psyche, we might ask why it would exist. Why would a woman cheat on a man, if that won't increase the number of her progeny—and if, moreover, she thus risks incurring the wrath, and losing the investment, of her mate? What reward could justify such a gamble? There are more possible answers to this question than you might imagine.
First, there is what biologists call "resource extraction."
If female humans, like female hanging flies, can get gifts in exchange for sex, then the more sex partners, the more gifts. Our closest primate relatives act out this logic. Female bonobos are often willing to provide sex in exchange for a hunk of meat. Among common chimpanzees, the food-for-sex swap is less explicit but is evident; male chimps are more likely to give meat to a female when she exhibits the red vaginal swelling that signifies ovulation.
Human females, of course,
don't advertise their ovulation. One theory about this "cryptic ovulation" sees it as an adaptation designed to expand the period during which they can extract resources. Men may lavish gifts on them well before or past ovulation and receive sex in return, blissfully oblivious to the fruitlessness of their conquest.
Nisa, a woman in a !Kung San hunter-gatherer village, spoke candidly with an anthropologist about the material rewards of multiple sex partners. "One man can give you very little. One man gives you only one kind of food to eat. But when you have lovers, one brings you something and another brings you something else. One comes at night with meat, another with money, another with beads. Your husband also does things and gives them to you."
Another reason women might copulate with more than one man—and another advantage of concealed ovulation—is to leave several men under the impression that they might be the father of particular offspring. Across primate species, there is a rough correlation between a male's kindness to youngsters and the chances that he is their father. The dominant male gorilla, with his celestial sexual stature, can rest pretty much assured that the youngsters in his troop are his; and, although not demonstrative by comparison with a human father, he is indulgent of them and reliably protective. At the other end of the spectrum,
male langur monkeys kill infants sired by others as a kind of sexual icebreaker, a prelude to pairing up with the (former) mother. What better way to return her to ovulation—by putting an emphatic end to her breast-feeding—and to focus her energies on the offspring to come?
Anyone tempted to launch into a sweeping indictment of langur morality should first note that infanticide on grounds of infidelity has been acceptable in various human societies. In two societies men have been known to demand, upon marrying women with a past, that their babies be killed. And among the Ache hunter-gatherers of Paraguay, men sometimes collectively decide to kill a newly fatherless child.
Even leaving murder aside, life can be hard on children without a devoted father. Ache children raised by stepfathers after their biological fathers die are half as likely to live to age fifteen as children whose parents stay alive and together. For a woman in the ancestral environment, then, the benefits of multiple sex partners could have ranged from their not killing her youngster to their defending or otherwise aiding her youngster.
This logic doesn't depend on the sex partners' consciously mulling it over. Male gorillas and langurs, like the Trobriand Islanders as depicted by Malinowski, are not conscious of biological paternity. Still, the behavior of males in all three cases reflects an implicit recognition. Genes making males unconsciously sensitive to cues that certain youngsters may or may not be carrying their genes have flourished.
A gene that says, or at least whispers, "Be nice to children if you've had a fair amount of sex with their mothers" will do better than a gene that says, "Steal food from children even if you were having regular sex with their mothers months before birth."
This "seeds of confusion" theory of female promiscuity has been championed by the anthropologist Sarah Blaffer Hrdy. Hrdy has described herself as a feminist sociobiologist, and she may take a more than scientific interest in arguing that female primates tend to be "highly competitive . . . sexually assertive individuals." Then again, male Darwinians may get a certain thrill from saying males are built for lifelong sex-a-thons. Scientific theories spring from many-sources. The only question in the end is whether they work.
Both of these theories of female promiscuity—"resource extraction" and "seeds of confusion"—could in principle apply to a mate-less woman as well as a married one. Indeed, both would make sense for a species with little or no male parental investment, and thus may help explain the extreme promiscuity of female chimpanzees and bonobos. But there is a third theory that grows uniquely out of the dynamics of male parental investment, and thus has special application to wives: the "best of both worlds" theory.
In a high-MPI species, the female seeks two things: good genes and high ongoing investment. She may not find them in the same package. One solution would be to trick a devoted but not especially brawny or brainy mate into raising the offspring of another male. Again, cryptic ovulation would come in handy, as a treachery facilitator. It's fairly easy for a man to keep rivals from impregnating his mate if her brief phase of fertility is plainly visible; but if she appears equally fertile all month, surveillance becomes a problem. This is exactly the confusion a female would want to create if her goal is to draw investment from one man and genes from another. Of course, the female may not consciously "want" this "goal." And she may not be consciously aware of when she's ovulating. But at some level she may be keeping track.
Theories involving so much subconscious subterfuge may sound too clever by half, especially to people not steeped in the cynical logic of natural selection. But there is some evidence that women are more sexually active around ovulation. And
two studies have found that women going to a singles bar wear more jewelry and makeup when near ovulation. These adornments, it seems, have the advertising value of a chimpanzee's pink genital swelling, attracting a number of men for the woman to choose from. And these decked-out women did indeed tend to have more physical contact with men in the course of the evening.
Another study, by the British biologists R. Robin Baker and Mark Bellis, found that women who cheat on their mates are more likely to do so around ovulation. This suggests that often the secret lover's genes, not just his resources, are indeed what they're after.
Whatever the reason(s) women cheat on their mates (or, as biologists value-neutrally put it, have "extra-pair copulations"), there's no denying that they do.
Blood tests show that in some urban areas more than one fourth of the children may be sired by someone other than the father of record. And even in a !Kung San village, which, like the ancestral environment, is so intimate as to make covert liaison tricky, one in fifty children was found to have misassigned paternity. Female infidelity appears to have a long history.
Indeed, if female infidelity
weren't a long-standing part of life in this species, why would distinctively maniacal male jealousy have evolved? At the same time, that men so often invest heavily in the children of their mates suggests that cuckoldry hasn't been rampant; if it had, genes encouraging this investment would long ago have run into a dead end.
The minds of men are an evolutionary record of the past behavior of women. And vice versa.
If a "psychological" record seems too vague, consider a more plainly physiological bit of data: human testicles—or, more exactly, the ratio of average testes weight to average male body weight.
Chimpanzees and other species with high relative testes weights have "multimale breeding systems," in which females are quite promiscuous. Species with low relative testes weights are either monogamous (gibbons, for example) or polygynous (gorillas), with one male monopolizing several families. (
Polygamous is the more general term, denoting a male
or a female that has more than one mate.) The explanation is simple.
When females commonly breed with many different males, male genes can profit by producing lots of semen for their transportation. Which male gets his DNA into a given egg may be a question of sheer volume, as competing hordes of sperm do subterranean battle. A species' testicles are thus a record of its females' sexual adventure over the ages.
In our species, relative testes weight falls between that of the chimpanzee and the gorilla, suggesting that women, while not nearly as wild as chimpanzee females, are, by nature, somewhat adventurous.
Of course, adventurous doesn't mean unfaithful. Maybe women in the ancestral environment had their wild, unattached periods— during which fairly weighty testicles paid off for men—as well as their devoted, monogamous periods. Then again, maybe not. Consider a truer record of female infidelity: variable sperm density.
You might think that the number of sperm cells in a husband's ejaculate would depend only on how long it's been since he last had sex. Wrong. According to work by Baker and Bellis, the quantity of sperm depends heavily on the amount of time a man's mate has been out of his sight lately. The more chances a woman has had to collect sperm from other males, the more profusely her mate sends in his own troops. Again: that natural selection designed such a clever weapon is evidence of something for the weapon to combat.
It is also evidence that natural selection is fully capable of designing equally clever psychological weapons, ranging from furious jealousy to the seemingly paradoxical tendency of some men to be sexually aroused by the thought of their mate in bed with another man. Or, more generally: the tendency of men to view women as possessions. In a 1992 paper called "The Man Who Mistook His Wife for a Chattel," Wilson and Daly wrote that "men lay claim to particular women as songbirds lay claim to territories, as lions lay claim to a kill, or as people of both sexes lay claim to valuables. . . .
Referring to man's view of woman as 'proprietary' is more than a metaphor: Some of the same mental algorithms are apparently activated in the rharital and mercantile spheres."
The theoretical upshot of all this is another evolutionary arms race. As men grow more attuned to the threat of cuckoldry, women should get better at convincing a man that their adoration borders on awe, their fidelity on the saintly. And they may partly convince themselves too, just for good measure. Indeed, given the calamitous fallout from infidelity uncovered—likely desertion by the offended male, and possible violence—female self-deception may be finely honed. It could be adaptive for a married woman to not
feel chronically concerned with sex, even if her unconscious mind is keeping track of prospects and will notify her when ardor is warranted.
[Bold mine. I'll stop here as this is going beyond fair use. But the whole book is really fascinating and deserves a spot on your bookshelf. -g]
