They picked the wrong target. Wilson's proposal was surely right. Nor does his work--if carefully read--give ammunition to conservatives or misogynists. Since then, empirical work by biologists studying many vertebrate species, including monkeys, apes , and even human beings, has found support for Wilson's basic idea. We almost certainly owe some of our social behavior to the trials and tribulations that our Pleistocene ancestors endured and survived. For example, no known human society consists of h undreds of hermits who live alone. Yet, adult animals in many species do live as hermits. In the Pleistocene, as best we can reconstruct by studying hunter-gatherers today, human hermits had poor odds of survival. Unlike orangutans, humans are too weak and our youngsters are too dependent for too long, for us to pull off living solo in the forest.
This attempt to explain some sociological findings by appealing to biology is called "sociobiology." Scholarship has marched on. Now the question is, can scientists explain some psychological findings by appealing to biology? Psycholo gists making the effort call it "evolutionary psychology" (they could have done worse).
David Buss, a psychology professor at the University of Michigan, is an ambitious evolutionary psychologist. He hopes to explain people's sexual feelings and behavior by appealing to evolution: how women and men choose their spouse, why some adults see k other sexual partners, why people feel jealousy, value beauty in their partner, and so on. He's also intrigued by possible differences between men and women.
You've heard evolutionary arguments of this sort before. Women and men face different problems and opportunities, because of the differences in how they reproduce. Women can have only one baby each nine months, plus recovery time. Men can have many mo re. Women face high physical costs during gestation, since they have to lug the fetus around and find and eat extra food to support it. Men don't. Long ago, before baby bottles and formula, women also had to spend time and caloric energy nursing their babies for many months each. Men didn't.
Males and females in other mammalian species differ in the same ways. Biologists have developed theories about how those differences might lead to differences in their sexual behavior. For example, a male who has an innate propensity to mate with many females during their fertile period may have many offspring who survive and inherit the same propensity to mate like crazy. Females don't increase the number of their offspring by increasing their number of mates during any given fertile period. So fema les with the same propensity won't leave behind a disproportionate number of grandchildren who mate like crazy. Biologists have good evidence that supports that theory. Of course, their observations of animals in the wild forced them to refine the theor y a lot. (In species whose babies need the care of two adults, monogamous fathers outreproduce promiscuous ones. In species where strange males attack babies, females improve their reproductive success by using sex to create alliances.)
"Theory, schmeory," you may say. "What evidence is there that any of this speculation applies to human beings, those highly refined products of culture, religion, and MTV?"
Good question. In his fine, readable book, The Evolution of Desire (BasicBooks, 1994), Buss reports the findings of his own international research on the preferences of thousands of men and women. He summarizes other researchers' findings, too. Here I'll focus on one theoretical proposal he makes and the evidence he offers to support it.
Buss thinks that ancient evolutionary pressures have left modern women with an innate psychological propensity to seek out a husband who is a good provider. The theory is impeccable. Pregnancy, nursing, and the long clumsy, dependent childhood of human babies meant that ancient women needed a partner who was good at hunting. Even if ancient women were given the same training at hunting as young men, their reproductive burdens would have handicapped them at it for long stretches of their adult lives. Women who had an innate psychological propensity to seek out a good hunter as a husband would have been more likely than less fussy women to actually choose a good hunter. Their smart choice would have improved their reproductive success. A higher perce ntage of their children would have survived than less fussy women's children. Some of their surviving daughters would have carried and passed on the propensity to look for a good hunter. After a few millenia, women who sought good hunters would have pre dominated.
What's the evidence? Buss reports that surveys of women in the U.S. in 1939, 1956, 1967, and the mid-1980's found that women said they valued high income potential in a mate roughly twice as much as men said they did. Buss's own study in the late 1980 's of over 10,000 people in 37 cultures ranging from Canada to Zambia, on 6 continents, found the same thing.
Not bad. However, it's not good enough. This evidence is perfectly consistent with my theory, which is that economic pressures that women face during their own lifetimes--as opposed to pressures faces by their ancestors thousands of years ago--account for their preference for a good provider. In each of the cultures surveyed, including the United States of the late 1980's, nearly all women expect to have children and nearly all expect that they will be the parent with primary responsibility for raisin g them. You cannot be a primary parent and simultaneously maximize your income. Most women would rather have more money than less. Ergo, most women seek a partner who will maximize his income, and rather a nice one at that, thank you.< p> Buss is well-aware of competing theories that stress women's position in society today. He offers two pieces of counter-evidence. The first is that in some societies where women are powerful, they still look for a rich husband. His example is the Bakw eri people in the Cameroons. Bakweri women in the 1950's had a good negotiating position because they were far outnumbered by the men. The sex ratio was roughly 236 men for each 100 women, because male laborers poured into the area to work on plantation s. The imbalance also created an opportunity for women to earn much more cash than men, if they became prostitutes. One result was that women changed husbands if they found a willing man with a higher income.
My response is that women who are awash with penniless laborers and opportunities for prostitution don't have oodles of power. More to the point, Bakweri women lived in a traditional society without safe bottle-feeding, expected to have many children, a nd expected to be the primary parent for each of them. The traditional sexual division of labor imposed tight constraints on how they could spend their time and energy for most of their adult lives. They needed a partner who was a good provider.
Buss's second piece of counter-evidence is stronger. Surveys in the U.S. in the late 1980's and early 1990's of professional women, such as medical and law students, have found that they put a high value on potential husbands' earning ability. Unlike t he Bakweri, those were women who really were powerful. I'd add that they were also women living with historically unprecedented advantages. Most expected to have only a few children, could use formula, and weren't required by practical constraints to be the primary parent. They didn't need a partner who would support them.
So what gives? Two things. First, most of those women expected to be the primary parents of their children. They didn't know if they'd take time off from paying work while their children were small. Marrying a man with a high income was like buying i nsurance. If they decided to quit medicine or law for a while, or even shift to a part-time job, they were covered.
Second, even the women who didn't have well-defined, conscious expectations about parenthood grew up in a country--the U.S. of the 1960's and 1970's--where one never saw a married father who was the primary parent and had a healthy wife. American cultur e, along with economic concerns, shaped their attitudes. Those attitudes included notions of motherhood as well as notions about what creates status in men. High-status women always seek high-status men (and vice-versa). As long as popular attitudes ma ke a man's income a very important part of his status, the conventionally-minded woman doctor will choose a high-earning man. This argument is compelling to me because we know that many other well-documented marital preferences are probably shaped by the surrounding cultural context and not innate. For example, in 1940, nearly all American Jews married other Jews. Now, the fi gure is only 50 percent. In some cases, it takes one or two generations for new opportunities to be reflected in people's marital preferences and behavior.
Here is a more striking example. Buss proposes that women also have an innate psychological propensity to seek a husband who is few years older. Older men command more resources than younger men. They don't stampede to marry men who are lots older, bec ause men who are lots older have a higher risk of dying soon. Again, the theory is impeccable. There is also decent evidence for it. In nearly all societies that have been studied, husbands are several years older than their wives.
I have a piece of counter-evidence, though. In the U.S. in 1900, the average groom was four years older than his bride, in first marriages for both. Now, the difference is 2.2 years. In 1970, in first marriages for both, only 12 percent of brides were older than their grooms. By 1988, 20 percent were.* To me, those figures suggest that because women's own earning ability and actual earnings have increased, they can afford to choose younger men.
Buss says repeatedly that the innate propensities he proposes may be weak. They may not be expressed at all in some social and economic contexts. He is even-handed, fair, and without doubt a good feminist. The question is, is he right? I think that my theory--mostly economic, emphasizing the importance of the sexual division of labor after birth, with a smidgeon of cultural influence--explains the available evidence as well as his theory does. Are women biologically programmed, even w eakly, to seek husbands who are good providers? The real answer is, we don't know. In order to know who high-earning women will marry in the future, we'll just have to wait and see.
*Cherlin, Andrew, letter to me dated February 18, 1993, citing Current Population Reports, 1992, P-20, no. 461, and unpublished research by the U.S. Bureau of the Census.
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