Why Beautiful People Have More Daughters: From Dating, Shopping, and Praying to Going to War and Becoming a Billionaire–Two Evolutionary Psychologists Explain Why We Do What We Do (5 page)

Since the advent of agriculture about ten thousand years ago and the birth of human civilization which followed, humans have not had a stable environment against which natural selection can operate. For example, a mere two centuries (ten generations) ago, the United States and the rest of the Western world were largely agrarian; most people were farmers. In the agrarian society, men achieved higher status by being the best farmers; those who possessed certain traits that made them good farmers had higher status and thus greater reproductive success than others who didn't possess such traits.

Then, only a century later, the United States and Europe were predominantly industrial societies; most men made their living working for factories. Traits that make men good factory workers (or, better yet, factory
owners
) may or may not be the same as the traits that make them good farmers. Certain traits—such as intelligence, diligence, and sociability—probably remain important,
³¹
but others—such as a feel for nature, the soil, and animals, and the ability to work outdoors or forecast weather—cease to be important, and other traits—such as punctuality, the ability to follow instructions, a feel for machinery or mechanical aptitude, and the ability to work
indoors
—suddenly become important.

Now we are in a post-industrial society, where most people work neither as farmers nor factory workers but in the ser vice industry. Computers and other electronic devices become important, and an entirely new set of traits is necessary to be successful. Bill Gates and Sir Richard Branson (and other successful men of today) may not have made particularly successful farmers or factory workers. All of these dramatic changes happened within ten generations, and there is no telling what the next century will bring and what traits will be necessary to be successful in the twenty-second century. We live in an unstable, ever-changing environment, and have done so for about ten thousand years.

For hundreds of thousands of years before that, our ancestors lived as hunter-gatherers on the African savanna, in a stable, unchanging environment to which natural selection could respond. That is why all humans today have traits that would have made them good hunter-gatherers in Africa—men's great spatiovisual skills, which allowed them to follow animals on a hunting trip for days and for miles without a map or a global satellite positioning device and return home safely; and women's great object location memory, which allowed them to remember where fruit trees and bushes were and return there every season to harvest, once again without maps or permanent landmarks.

For the last ten thousand years or so, however, our environment has been changing too rapidly for evolution to catch up. Evolution cannot work against moving targets. That's why humans have not evolved in any predictable direction since about ten thousand years ago. We hasten to add that certain features of our environment have remained the same—we have always had to get along with other humans, and we have always had to find and keep our mates—so certain traits, like sociability or physical attractiveness, have always been favored by natural and sexual selection. But other features of our environment have changed too rapidly relative to our generation time, in a relatively random fashion—who could have predicted computers and the Internet a century ago?—so we have not been able to adapt and evolve against the constantly moving target of the environment.

Much of our discussion in the following chapters hinges on differences between men and women. Now
everyone knows
that men and women are different. On the whole, they want different things, they are good at different things, and they behave in different ways. While everybody may know
that
men and women are different, they may not know
why
. Or they may think they do, but they might be wrong.

The prevailing explanation in the Standard Social Science Model, popular among academic social scientists and the general population alike, is
gender socialization
. According to this explanation, men and women (and boys and girls) think and behave differently because they have been socialized differently by their culture and society. Recall that the Standard Social Science Model contends that human nature is a blank slate (principle 3). Male and female babies are born identical except for a few anatomical differences,
but these anatomical differences do not include the brain
(principle 2). Since the day of their birth, boys and girls are treated differently and socialized either as boys or girls. Boys are encouraged to be aggressive and violent (by being given toy trucks and toy guns), while girls are taught to be caring and nurturing (by being given dolls and tea sets). Gender socialization permeates every aspect of culture and society (it is done not only by the parents but by educational, religious, political, and economic institutions and the media) and continues throughout the life course, and its effects are cumulative. By the time boys and girls grow up to be men and women, they think and behave differently because “society” expects them to, and the sex differences are apparently permanent. However, the Standard Social Science Model contends that if parents and “society” provide gender-neutral, androgynous socialization to children, then boys and girls will not behave differently, and men and women will be the same in their behavior, cognition, values, and preferences.

An overwhelming amount of evidence now available from science unambiguously demonstrates that this view is false. We will discuss only two recent studies here, and refer interested readers to more comprehensive reviews.
¹

Sex Differences Appear on the First Day of Life

University of Cambridge psychologist Simon Baron-Cohen and his associates have conducted a careful experiment with one-day-old babies.
²
They simultaneously presented a picture of a woman's face and a mechanical mobile to 102 newborn babies (44 boys and 58 girls, but the researchers themselves were blind to the sex of these babies until after the experiment was finished). They videotaped the babies to mea sure which object they paid more attention to. Their analysis showed that more boys preferred to look at the mechanical mobiles, and boys on average gazed at them longer. In contrast, more girls preferred to look at the human face, and girls on average gazed at it longer.
Everybody knows
that boys and men tend to have greater interest in machines and other mechanical objects, and girls and women tend to be more social and express greater interest in relationships with others. If these sex differences are mostly the outcome of lifelong gender socialization, as the Standard Social Science Model claims, how can newborn babies who are just twenty-four hours old exhibit the same sex difference? Not even the most ardent supporters of the Standard Social Science Model would contend that twenty-four hours is enough for gender socialization.

Sex Differences Are Shared by Monkeys

In a very ingenious experiment, Gerianne M. Alexander and Melissa Hines gave two stereo typically masculine toys (a ball and a police car), two stereo typically feminine toys (a soft doll and a cooking pot), and two neutral toys (a picture book and a stuffed dog) to 44 male and 44 female vervet monkeys.
³
They then assessed the monkeys' preference for each toy by mea suring how much time they spent with each. Their statistical analysis demonstrated that male vervet monkeys showed significantly greater interest in the masculine toys, and the female vervet monkeys showed significantly greater interest in the feminine toys. The two sexes did not differ in their preference for the neutral toys. Alexander and Hines' article contains pictures of a female vervet monkey examining the genital area of the doll in an attempt to determine whether it is male or female, as a girl might, and of a male vervet monkey pushing the police car back and forth, as a boy might. If children's toy preferences were largely formed by gender socialization, as the Standard Social Science Model claims, in which their parents give “gender-appropriate” toys to boys and girls, how can these male and female vervet monkeys have the same preferences as boys and girls? They were never socialized by humans, and they had never seen these toys before in their lives.

As these two studies (and numerous others) show, the sex differences in behavior, cognition, values, and preferences are largely innate; universal across cultures; and, in many cases, constant across species.
⁴
If the sex differences were the result of social and cultural practices such as gender socialization, then they should by definition vary by culture and society. In fact, however, in every human society (and among many other species), males on average are more aggressive, violent, and competitive, and females on average are more social, caring, and nurturing. What is constant in every culture and society (sex differences in behavior) cannot be explained by what is variable across cultures and societies (cultural and social practices). A variable cannot explain a constant; only a constant can explain a constant.

A Consequence, Not a Cause

Rather than the results of lifelong gender socialization, sex differences in behavior, cognition, values, and preferences are part of innate and distinct male and female human natures; men and women are hardwired to be different. Male and female human brains are different, just like male and female reproductive organs are different. Gender socialization helps to accentuate, solidify, perpetuate, and strengthen the innate differences between men and women, but it does not
cause
or
create
such differences. In other words,
men and women are not different because they are socialized differently; they are socialized differently because they are different.
Gender socialization is not the cause of sex differences; it is their consequence.

If gender socialization is not the cause of sex differences, then what is? What is the constant that explains the universal sex differences? It turns out that two simple biological facts lead to a whole array of sex differences: anisogamy and the internal gestation of fertilized eggs within the female body.
Anisogamy
means that the female sex cell (egg) is larger in size and fewer in number than the male sex cell (sperm). (This, by the way, is the biological definition of male and female. The female of any sexually reproducing species is defined as the sex that produces the larger sex cell, and the male, by default, is the other sex.) Anisogamy means that the egg is biologically far more valuable than the sperm; in nature, the sperm is abundant (practically infinite) in supply and biologically less costly to produce than the eggs. A quick rule of thumb in biology, which can explain a lot of sex differences in many species, is:
Sperm is cheap.

The
internal gestation
of fertilized eggs within the female body means, among other things, that the female can produce far fewer offspring than the male can. It takes a woman at least nine months, usually a few years, to produce one child (because a woman is usually infertile while she nurses her baby); it takes a man fifteen minutes. A woman can normally have at most twenty to twenty-five pregnancies in her entire lifetime, usually far less; there is no limit to the number of children men can potentially produce. The operative term here, of course, is
potentially
.

Anisogamy and the internal gestation within the female body combine to produce a very important consequence: sex difference in fitness variance.
Fitness variance
is the difference between the “winners” and the “losers” in the reproductive game—how much more reproductively successful the winners are compared to the losers. Because of anisogamy and internal gestation, men have much greater fitness variance than women. Men's greater fitness variance means two things. First, looking at the bottom of the distribution, far more men remain childless than women, whereas relatively fewer women remain childless for life. So one consequence of greater fitness variance among men is that the
fitness floor
(the worst one can possibly do) is much lower for men than for women. The worst on average is much worse for men than for women.

Second, looking at the top of the distribution, a few men have a far larger number of children than any woman could possibly have. It is possible for some men to have dozens, hundreds, even thousands of children in their lifetimes, whereas a woman is limited to at most about twenty-five pregnancies in life. The other consequence of greater fitness variance among men is that the
fitness ceiling
(the best one can possibly do) is much higher for men than for women. The best is much better for men than for women. Fitness variance is the distance between the ceiling (the best) and the floor (the worst), so it is much greater for men than for women.

Even though anisogamy and the internal gestation within the female body makes greater fitness variance among men than among women
possible
, what actually produces it in reality is the fact that humans are naturally polygynous.
⁵
There is much confusion about terminology for different institutions of marriage, even among social scientists.
Monogamy
is the marriage of one man to one woman.
Polygyny
is the marriage of one man to more than one woman, while
polyandry
is the marriage of one woman to more than one man.
Polygamy
(although it is often used synonymously with polygyny in casual conversations) refers to both polygyny and polyandry. Because of its ambiguity, the word
polygamy
should not be used unless it specifically and simultaneously refers to both polygyny and polyandry.

Until very recently, humans were mildly polygynous throughout their evolutionary history.
^[6]
Under polygyny, some men get more than their “fair share” of mates, leaving others with none. Thus, virtually all women, but not all men, get to reproduce, but those men who do, get to reproduce a large number of children. This is why few women, but relatively more men, have zero children (complete reproductive failure).

The largest number of children that a woman has ever had is sixty-nine. The wife of an eighteenth-century Russian peasant, Feodor Vassilyev, had twenty-seven pregnancies in her life, including sixteen pairs of twins, seven sets of triplets, and four sets of qua druplets; amazingly, Mrs. Vassilyev never had any single births in her life! And all but two of her sixty-nine children survived to adulthood. In contrast, the largest number of children that a man has ever had is
at least
1,042.
^[7]
The last Sharifian emperor of Morocco, Moulay Ismail the Bloodthirsty, maintained a large harem, as many ancient rulers did,
⁸
and had at least 700 sons and 342 daughters. (The exact number of children that Moulay Ismail had in his lifetime is lost to history, however, because they stopped counting them after a while.)

Exactly how many children Moulay Ismail the Bloodthirsty and Mrs. Feodor Vassilyev had is not important. What's important is this: The largest number of children that a man can potentially have is
two orders of magnitude greater
than the potential number of children that a woman can have (thousands vs. tens), while many men, but few women, face a great chance of ending their lives as total reproductive losers (leaving no offspring).

Worth the Fight

As we will discuss repeatedly throughout this book, the greater fitness variance among men, rather than gender socialization, is the reason why men are much more aggressive, competitive, and violent than women. Men gain far more by competing with each other for access to mates, whereas the benefit of competition for women in reproductive terms is far less. If men compete successfully and gain reproductive access to a large number of women, they can potentially have hundreds, if not thousands, of children; if they fail to compete successfully, they face a distinct possibility of having no children at all. So the difference between a potential reward for competition and the potential cost of not competing is tremendous; they might as well compete. The same difference for women is much smaller. If women compete successfully and gain reproductive access to a large number of men, they can realistically have twenty to twenty-five children at most (in the absence of multiple births, which is beyond their control); if they fail to compete successfully, they might only have one or two children. The potential benefit of competition does not justify the potential costs (injury or death). This is why women are on the whole not as aggressive, competitive, or violent as men.
⁹

The much higher fitness ceiling for men than for women also means that women make a far greater investment into their children than men do. While
reproductive success
is equally important for men and women (as it is for all living creatures),
each child
is far more important to a woman (as it is to females of all mammalian species) than it is to a man (as it is to males of all mammalian species). Each child represents a much greater portion of a woman's lifetime reproductive potential than it does a man's. It represents perhaps one-twentieth of a woman's lifetime reproductive potential; it represents one one-thousandth of a man's. Anisogamy and internal gestation thus lead to a large number of sex differences in behavior that we will discuss in subsequent chapters.