by David L. Brooks
In This Issue:
—Mating Minds, by Geoffrey Miller
—Why do men help raise the kids?
—Brad Pitt need not apply
—How to live to 100
—The kindness of strangers
******************************************
—Mating Minds: How Sexual Choice Shaped the Evolution of Human Nature
by Geoffrey Miller
Anchor Books, 2000
Natural selection is a powerful idea which explains much about why we are the way we are. But it by no means explains all. The trouble with natural selection, says Geoffrey Miller, is that "Nobody has been able to suggest any plausible survival payoff for most of the things that human minds are uniquely good at, such as humor, story-telling, gossip, music, self-consciousness, ornate language, imaginative ideologies, religion, and morality."
Enter sexual selection. "Sexual selection is unusually fast, powerful, intelligent, and unpredictable. This makes it a good candidate for explaining any adaptation that is highly developed in one species but not in other closely related species that share a similar environment." Miller's book is a startling and wide-ranging account just how much we owe to sexual selection.
Miller takes us on a tour through sexual selection, showing how it explains details of our bodies—penises, breasts, buttocks, beards, head hair, and full lips—just as it explains the peacock's tail or the lark's song. But it is when he turns his attention to those behaviors we cherish as definitively human that it gets interesting.
Miller proposes that, just as physical symmetry or large breasts are fitness indicators of good physical health, so the health of the brain has its own set of fitness indicators. "The healthy brain theory suggest that our brains are different from those of other ape species not because extravagantly large brains helped us to survive or raise offspring, but because such brains are simply better advertisements of how good our genes are."
The human brain is about 2% of body weight, but consumes 15% of oxygen intake, 25% of metabolic energy, and 40% of blood glucose. "If we view the human brain as a set of sexually selected fitness indicators, its high costs are no accident. They are the whole point. The brain's costs are what make a good fitness indicator. Sexual selection made our brains wasteful, if not wasted: it transformed a small, efficient ape-style brain in to a huge energy-hungry handicap spewing out luxury behavior like conversation, music, and art." The mind is ornamental as is the peacock's tail and serves the same purpose.
But what are these ornaments? Miller argues that sexual selection played a part in the development of a whole list of human traits including morality, charity, generosity, sympathy, sexual fidelity, language, and creativity. It's not possible in a short review to do justice to this thesis, but let me outline his argument for language as a sexually selected fitness indicator, just to give you the flavor.
Miller points out that "If language evolved in part through sexual choice as an ornament or indicator, it should be costly, excessive, luxuriant beyond the demands of pragmatic communication." So consider this: The average primate knows 5 to 20 distinct calls. The most frequent 100 words account for about 60% of all conversation; and the most frequent 4,000 words account for about 98% of conversation. But the average English speaker knows 60,000 words. Now that is extravagance. But how could sexual selection produce the luxuriance we know as language?
People try to make the best selection of mates from those available to them. To do this they use every scrap of information that comes their way. They can see fitness indicators like symmetry or clear skin, they can see indicators like status. But once language began to develop "each person's entire history became a part of their 'extended phenotype' in courtship. Like our body ornaments, our pasts became part of our sexual display." The result was that "at each step, both individuals were trying to extract, by using the language available to them, as much information as they could. The more talking they did, the more of their minds they revealed. The more verbal courtship revealed, the greater effect sexual selection could have."
Language not only revealed our pasts to each other, but also our creativity and our sense of humor. Stories, poems, and songs say as much about a person as autobiography. Language not only allows all of that, coupled with sexual selection it positively encourages it.
The central idea of this wonderful book is simply stated: "Our ancestors favored kind, fair, brave, will-mannered individuals who had the ability and generosity to help their sexual partners, children, step-children, and other members of their tribe. They were sexually unattracted to cheats, cowards, liars, and psychopaths. Is that really so hard to believe?"
It's not hard to believe. But neither does it do justice to this startling and wide-ranging book. Expose yourself to a powerful idea which will change the way you look at human beings and their mating behavior—whether it's your teenager on the phone for hours with their boy/girlfriend or Shakespeare writing sonnets to his dark lady. Buy this book.
Highly recommended.
—Why do men help raise the kids?
Considering that for our closest relatives, chimps, monogamy is not even an option and males play almost no role in raising kids, it's odd that we are mostly monogamous and males play a relatively large role in raising kids. So, is monogamy and child raising by human males something that evolved or is it something enforced by culture? It's probably a bit of both. As Geoffrey Miller argues in the book reviewed above, women try to select the best mate they can find. Since a caring male is an asset, she will look for a mate who cares. And if she can find a reliable fitness indicator for caring, then sexual selection will work its magic as dads out-reproduce cads. And once caring becomes common enough in the population, it will become the behavioral norm and be incorporated in the customs, and perhaps the laws, of the society.
—Brad Pitt need not apply
So, if women prefer the square jaw and rough-chiseled features of manly men, how come guys like me find wives? Well, it's not as simple as it sounds. Some recent research shows that women prefer the Brad Pitt types when they're at their most fertile and when they rate themselves as attractive. Apparently, those manly types are also seen as not too reliable, so if a woman has a reliable sort around the house they might find a fling with those handsome types appealing. But only if the women rate themselves as attractive. It might be that since Brad and his buds can get all the chicks they can handle, unless a women feels that she's got a chance in the competition she's better off giving him a miss. Which is OK with me.
—How to live to 100
In at least one respect we've broken the bounds of evolution: we live a lot longer than than evolution designed us for. From an evolutionary point of view, we're just here to get our genes into the next generation (and see that generation to adulthood). The life expectancy of our Pleistocene forbearers was probably somewhere between 25 and 30—about what you would expect if we reach sexual maturity at about 15. But life expectancy in the West is in the mid-to-high 70s for men and the low 80s for women. Between 40 and 90 we die of things our ancestors rarely did: cancer, heart disease, and the like. After 90 you've outlived most of the things that kill younger people. So what do you need to see triple figures? A healthy lifestyle and keeping fit, an active brain, and a good dose of luck (to avoid bad genes and fatal accidents).
—The kindness of strangers
As much as we differ from chimps, we also find the roots of many human behaviors in chimp behaviors. For instance, we cooperate extensively with strangers. How is that? It appears that this sort of cooperation beyond family ties is also found in chimp society. Five years of observations of chimps in the wild in Kibale National Park, Uganda, have shown that unrelated, or only distantly related, males cooperated with each other hundred of times to either defend the band or share meat. And they did it for the same reason we cooperate: they expected those actions to be reciprocated. The fact that both chimps and humans act this way suggests that the behavior has its roots in the behavior of our common ancestor before the human and chimp lineages split some six million years ago. The expectation of the kindness of strangers goes back well before Blanche DuBois.
******************************************
Copyright 2007 The Bio-Rational Institute
******************************************
