Decoding Love Page 7
THE MACHIAVELLIAN MIND
Distressing though this is, our social skills (a much nicer expression than deception) are quite possibly the key to understanding how the human brain evolved. One of the leading theories for why human beings developed large brains is called the social brain hypothesis, also known rather chillingly as the Machiavellian intelligence theory. The idea is that the size of our social groups has played the essential role in pushing humans to develop larger brains. Many primates, such as chimpanzees, live in reasonably large troops, usually between twenty to fifty members. But no animal is more social and lives in larger groups than man. There are many advantages to larger groups, but there is one serious disadvantage: negotiating relationships with all the members of the group. Rewarding friends, seeking allies, and avoiding enemies all require more brainpower as the group gets larger. Researchers have found that the larger an animal’s group size, the larger the percentage of the brain devoted to the neocortex (the outer layer of the brain, which accounts for most cognitive abilities). For most mammals, the neocortex makes up 30-40 percent of the brain. For highly social primates, such as chimpanzees, the percentage rises to 50 to 65 percent. For humans, the neocortex takes up a staggering 80 percent of the brain (and our brains are seven times larger than you would expect for a mammal of our size).
According to social brain theorists, the size of human groups also played a key role in the evolution of language. For other primates, the glue that keeps the group in relative harmony is grooming—that staple activity of animal behavior, for example, when one chimpanzee combs through the hair of another to untangle fur or remove nits. This is done not just for reasons of hygiene but also to reaffirm the social bond between the two. Primatologists have charted a linear relationship between the size of the group and the amount of time spent grooming. But grooming is time consuming, too time consuming for humans once their group size began to grow beyond fifty. Imagine trying to use grooming to hold together a large corporation. Nothing would ever get done. So, language came to serve as a kind of accelerated social grooming, allowing group members to maintain relationships on a much larger scale. For social brain theorists, language developed not primarily for informational tasks, such as where to find a wildebeest, but so that we could gossip about one another. Gossip served not as a distraction from the task at hand but as the main business, establishing and defining our relationships with other members of the group. Who shares meat, which person can’t be trusted, who cheats on whom. Gossip became the means of handling our ever-expanding social networks. Lest you think we have evolved beyond that today, studies show that fully 60-70 percent of our conversations are devoted to social topics (i.e., gossip).
Of course, as Ekman’s eighteen lying smiles already revealed, social life and gossip are firmly intertwined with deception. You see, a larger neocortex doesn’t just predict the size of a species’ social group. It also predicts how much that species uses duplicity and social manipulation. The proponents of the social brain theory are still wrestling with perhaps the central question it raises about our development: is our brain growth directed more toward enabling us to connect with one another or more toward allowing us to manipulate one another? Now you can see why this theory is also called Machiavellian.
If we take Darwin’s idea of sexual selection seriously, though, we can narrow the driving force behind brain growth even further. We may, in fact, be able to pin it entirely on the need to find a mate. In other words, the central purpose behind our enormous brains may be to help us negotiate the unruly world of dating. Evolutionary psychologist Geoffrey Miller, a leading proponent of this theory, has even gone so far as to call the human mind a “protean courtship device.”
The reason mating is a plausible force behind our brain growth is because of something known as runaway sexual selection, which occurs when both the trait and the preference for the trait are heritable. In this case, if the main social difficulty that we face as a species is securing a mate, and if the most essential trait to accomplish that is our intelligence, and if intelligence is heritable, then sexual selection will lead to greater intelligence. And if the preference for intelligence is also heritable, then sexual selection will boost human intelligence even more dramatically (this is where it becomes runaway). And what really supercharges runaway sexual selection in our species is that women are not the only ones looking for intelligence. Men also tend to want intelligence in their mates, although not quite as avidly as women. With both sides choosing for intelligence, you can see why “runaway” is a fairly apt description. I guess you could call this the Don Juan theory of human development.
Once you look at things through the lens of sexual selection, there is almost no aspect of human culture that remains untouched by it. Geoffrey Miller argues that most of our cultural behavior is largely instinctual and derived from sexual selection—not that we’re conscious of it. This isn’t a crude and straightforward expression of our sex drive or a case of Freudian sublimation; rather, sexual selection has hijacked qualities that were quite likely already being chosen through natural selection. To bolster his claim, Miller looked at when artists in different fields were most productive, and what he found was that male artists tend to peak around the age of thirty, which is strangely youthful if you think about the importance of artists maturing and developing, but an age that makes perfect sense if you think of artistic production as a means of attracting sexual partners. He also found that men produce vastly more than women. Of course, there is a cultural element to this, but Miller suggests that there is also a sexual element—that men are under more pressure to attract women (remember—cheap sperm, precious eggs). So, sexual selection taken to its logical extreme can explain virtually everything in human development from Bach to skyscrapers, because, at the end of the day, our intelligence has developed largely thanks to the pressures of finding a mate.
THE SEXY—OR AT LEAST SEXED—BRAIN
Even as both men and women have developed an extraordinarily large and complex neocortex, though, their brains have not grown in precisely the same way, which is exactly what we should expect given that each sex faces different evolutionary challenges. Before I delve into those differences, though, I want to make one thing absolutely clear: these remarks should not be taken as confirmation of sexual stereotypes. They are based on averages. On average, men may have a greater capacity for math, and women may have a better facility with language. But that does not mean that women can’t be brilliant mathematicians or that men can’t be excellent writers. Our sexual prejudices are so ingrained that the first part of that statement is essential, while no one needs to be reminded about the second part.
These sexual differences are not simply the result of cultural conditioning. They exist in the physical structure of the brain itself and are the result of a surge of testosterone released in male babies during fetal development. For example, women have roughly 11 percent more neurons in the part of the brain that handles language and hearing. Also, the hippocampus, which is the principal location of emotion and memory formation, is larger in women than men (perhaps finally providing an answer to many women’s frustrated sense that men never remember anything). And the brain center for observing emotion in others is more developed in women than men. Men’s brains tend to have larger areas devoted to action and aggression, and male brains devote more than two and half times the space than women’s to sex, although scientists have not yet determined how large a portion is devoted to sports. Because of these differences, women on average tend to be better with language, and men tend to be better at math and map reading.
These differences are so fundamental that, according to one study, the way men and women find their way through the world is different. When you present men with a maze, they tend to use geometric reasoning to move through it. Women, on the other hand, use landmarks. Both groups struggle when you force them to use the other sex’s method. And it is quite possible that even this is related to finding a mate because,
in a statement so obvious I almost blush to write it, first you have to literally find a mate. Men’s greater spatial skills when it comes to things like map reading likely aided them in their search. Women, as the precious egg holders, could sit around and wait for suitors to show themselves, much like Amanda Wingfield with her eighteen gentlemen callers in The Glass Menagerie. For evidence of this in the animal world, you only need look at the humble vole. We are interested in two particular species, the pine vole and the meadow vole. Pine voles are monogamous. The males and the females have similar brains, and each sex does about the same when required to run through a maze. The meadow vole, however, is polygamous, and males have to cover much greater distances than the females because they have to visit the different burrows of their various female partners. Not only does a male meadow vole have a bigger hippocampus than the female, he also is much better at finding his way through a maze. This may finally explain men’s unwillingness to ask for help when lost. Before the age of GPS, the ability to find one’s way was probably one of the tests of a man’s genetic fitness.
Needless to say, there are some fairly obvious differences when it comes to sex and the brain. When researchers scanned the brains of people watching a neutral conversation between a man and a woman, the male brains immediately showed activity in the sexual areas, while the women’s brains did not. As Louann Brizendine aptly put it in her fascinating book The Female Brain, men have an eight-lane superhighway in their brains when it comes to sex, while women have an eight-lane superhighway when it comes to emotion. But it’s not just sex. It appears that men and women also tend to fall in love differently. For men in love, the visual areas of the brain are the most active, while for women a number of different areas are involved.
This confirms what we have already found about human behavior, but what is fascinating is how the female brain has developed in ways that help women counter the ferocious sex drives of men. This is where her greater facility with language and emotion come into play. As we have seen, men are perfectly willing to lie about themselves or about their commitment in order to have sex, so women have to be good at spotting that deception. And a number of studies have found that women are better at reading the facial expression and emotional nuances of an encounter. For example, in one study, men were able to pick up signs of sadness in a female face only 40 percent of the time, while women succeeded 90 percent of the time. Women’s brains are also designed to remember the emotional details of an encounter. So, even on the level of brain development, men and women appear to be locked in an evolutionary struggle, what Geoffrey Miller has called “a never-ending arms race of romantic skepticism and excess.” And women continually hone their abilities as well. As I discussed in the last chapter, researchers have found that women often have detailed talks decoding encounters with the opposite sex or analyzing the character of a man, while men tend not to talk about those things very much. This will hardly come as a shock—women, after all, flock to Sex and the City, while men tune in to Entourage.
One controversial theory is that autism might be the result of an overly masculinized brain. I don’t want to make light of a serious condition, but given the vast differences on average between men and women when it comes to dealing with the intricacies of human relationships, such as intuiting the emotions of another, I think many women might find it useful when dating and even in long-term relationships to think of most men as slightly autistic compared to women.
THE IMPORTANCE OF WAIST-TO-HIP RATIOS AND OTHER ODD METRICS OF ATTRACTION
Okay, so we have these big brains, but are they hardwired to look for certain things? The romantic story line says no, claiming that we are all unique and that love itself is as varied as a snowflake. In this view, beauty is in the eye of the beholder. Love is blind. Yadda yadda yadda. But the scientific answer to this question is a resounding yes. Although science cannot explain the idiosyncratic reasons why you may prefer a partner who likes piña coladas, it can do a better job with general explanations of why you are attracted to someone than you can yourself.
First of all, let’s ditch the idea that beauty is subjective. It’s not. Studies have shown that even babies prefer attractive faces, so these preferences seem to be virtually hardwired into us—so much so that when hooked up to electrodes, people looking at beautiful female faces generated an extra electrical charge. And surveys show that there is strong agreement about whom people find attractive. Interestingly, composite pictures melding numerous faces always outscore individual faces in attractiveness and become more attractive the more faces you include, for the simple reasons that a more symmetrical face is the result. As we’ve already seen with the female orgasm, we’re big fans—albeit unwittingly—of symmetricality. Understanding why reveals the excellent evolutionary reasons for the way our desires have been shaped. In this case, being symmetrical is an excellent proxy for our general health. And how symmetrical you are is an excellent sign not just of how healthy you are now but also how healthy you have always been, since asymmetries tend to occur because of disease or illness during our fetal and childhood development. Hair is another good indicator, which helps explain the vast array of products directed at creating better-looking hair. Long, lustrous hair signals an equally long and robust good health. Skin acts as a similar signpost of health.
According to one theory, evolution has even added a wrinkle so that people with excellent genes can show off their fitness by displaying what evolutionary biologist Amotz Zahavi dubbed a “high cost signal.” Think back to Darwin and his original formulation of the survival of the fittest. When it comes to the utilitarian selection of certain qualities essential for the survival of a species—a gazelle’s speed or a bear’s claws—efficiency rules. When it comes to sexual selection, though, signaling to the opposite sex can involve a good bit of waste. Take, for example, the male peacock’s tail. It’s enormous, using a tremendous amount of the bird’s resources and making him more vulnerable to predators. But what it also does is signal to the female that he is so healthy, he doesn’t need to worry about hoarding his resources. In this way, the male peacock is able to distinguish himself from his moderately healthy peers. The high-cost signal can take all sorts of forms—think of the man who buys an expensive sports car as a signal that he has resources to burn. But we humans, like other animals, already have all sorts of high-cost “signals” built into us—as well as an unconscious desire to look for them in the opposite sex.
Think of the typical ideal for a man’s face—a large, square, “manly” jaw and chin. This ideal is so dominant that it is almost a visual cliché in our culture, and you would be hard-pressed to find a Hollywood leading man who doesn’t have that look. It turns out that women’s preference for that particular face is not merely some arbitrary aesthetic whim. You need a lot of testosterone during puberty to produce a face like that. The problem is that testosterone also suppresses the immune system and makes a young man more vulnerable to disease, so the ability to have such a face serves as a high-cost signal of genetic fitness. Only extremely fit individuals can afford that face and remain disease free.
Women have their own bodily signals. For instance, there is a very good reason men prefer full lips and why someone like Angelina Jolie is almost freakishly genetically fit. Although not a high-cost signal, those full lips require a woman to be hyperfeminine—at least when it comes to sex hormones. During puberty, the woman must experience both a surge of estrogen and a low level of testosterone. This also will give her a shorter, lower face, which will further feminize her look. And it turns out that there may be perfectly good evolutionary reasons why gentlemen prefer blondes. Blond hair is one of those traits that changes dramatically with age. Men who prefer blondes are likely unconsciously choosing them because their hair signals health and fecundity. One theory for why blond hair evolved in northern Europe is that the cold weather kept people covered in clothes so that women had to develop a way to advertise their youth that could be seen. Hence, blond hair.
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One of the best indicators of female genetic fitness is a rather bizarre ratio that most people have never heard of, let alone consciously considered. Waist-to-hip ratio. That’s right—not breast size or any of the other more obvious markers of beauty, but waist-to-hip ratio, which has an enormous influence on whether or not men find a woman attractive (the comparable male ratio is waist-to-shoulder). It turns out that the ideal ratio is 0.7 or, in layman’s terms, an hourglass figure. In one ingenious study, a researcher examined centerfolds from Playboy and beauty contest winners from the past several decades. While the women did get thinner on average during that period, their waist-to-hip ratio held steady at 0.7. Women may worry about being fat, but it turns out that it’s not how fat you are but how that fat is distributed. For example, one study found that heavy women with a low waist-to-hip ratio were preferred to thin women with a high ratio. Again, there is a very good reason for men’s preference. That waist-to-hip ratio is an excellent indicator not just of good health (many diseases have been linked to the ratios in which fat is distributed) but also of high fertility. A study of Polish women revealed that women with low waist-to-hip ratios also had high fecundity as measured by their reproductive hormones. And scientists have recently discovered yet another advantage. Fat in a woman’s hips and thighs is particularly good fat because there is a higher concentration of omega-3 fatty acids (which are important for brain development). A recent study has shown that children of these curvy mothers have better cognitive abilities than children of the less curvy, and the bigger the difference between the waist and the hips, the better the children did.