But the uniqueness of the individual is only the first of the implications of sex for human nature. Another is that there are, in fact, two human natures: male and female: The basic asymmetry of gender leads inevitably to different natures for the two genders, natures that suit the particular role of each gender. For example, males usually compete for access to females, rather than vice versa.
There are good evolutionary reasons for this, and there are clear evolutionary consequences, too; for instance, men are more aggressive than women.
A third implication of sex for human natures is that every other human being alive today is a potential source of genes for
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The Red Queen
your children. And we are descended from only those people who sought the best genes, a habit we inherited from them. Therefore, if you spot somebody with good genes, it is your inherited habit to seek to buy some of those genes; or, put more prosaically, people are attracted to people of high reproductive and genetic potential—the healthy, the fit, and the powerful. The consequences of this fact, which goes under the name of sexual selection, are bizarre in the extreme, as will become clear in the rest of this book: OURS TO REASON WHY?
To speak of the " purpose" of sex or of the function of a particular human behavior is: shorthand. I do not imply some teleological goal-seeking or the existence of a great designer with an aim in mind: Still less will I be implying foresight or consciousness on the part of "sex " itself or of mankind: I merely refer to the astonishing power of adaptation, so well appreciated by Charles Darwin and so little understood by his modern critics: For I must confess at once that I am an "adaptationist, " which is a rude word for somebody who believes that animals and plants, their body parts and their behaviors, consist largely of designs to solve particular problems.'
Let me explain: The human eye is " designed " to form an image of the visual world on its retina; the human stomach is
" designed " to digest food; it is perverse to deny such facts: The only question is how they came to be "designed " for their jobs.
And the only answer that has stood the test of time and scrutiny is that there was no designer. Modern people are descended mainly from those people whose eyes and stomachs were better at those jobs than other people 's. Small, random improvements in the ability of stomachs to digest and of eyes to see were thus inherited, and small diminishments in ability were not inherited because the owners, equipped with poor digestion or poor vision, did not live so long or breed so welclass="underline"
We human beings find the notion of engineering design quite easy to grasp and have little difficulty seeing the analogy with HUMAN NATURE
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the design of an eye: But we seem to find it harder to grasp the idea of "designed " behavior, mainly because we assume that purposeful behavior is evidence of conscious choice: An example might help to clarify what I mean: There is a little wasp that injects its eggs into whitefly aphids, where they grow into new wasps by eating the whitefly from the inside out: Distressing but true: If one of these wasps, upon poking its tail into a whitefly, discovers that the aphid is already occupied by a young wasp, then she does something that seems remarkably intelligent: She withholds sperm from the egg she is about to lay and lays an unfertilized egg inside the wasp larva that is inside the whitefly. (It is a peculiarity of wasps and ants that unfertilized eggs develop into males, while all fertilized ones develop into females.) The "intelligent" thing that the mother wasp has done is to recognize that there is less to eat inside an already-occupied whitefly than in virgin territory: Her egg will therefore grow into a small, stunted wasp. And in her species, males are small, females large. So it was "clever " of her to "choose " to make her offspring male when she "knew " it was going to be smalclass="underline" But of course this is nonsense: She was not "clever "; she did not " choose " and she " knew " not what she did: She was a minuscule wasp with a handful of brain cells and absolutely no possibility of conscious thought: She was an automaton, carrying out the simple instructions of her neural program: If whitefly occupied,
withhold sperm: Her program had been designed by natural selection over millions of years: Wasps that inherited a tendency to withhold sperm when they found their prey already occupied had more successful offspring than those that did not. Yet in exactly the same way that natural selection had "designed" an eye, as if for the "purpose " of seeing, so natural selection had produced behavior that seemed designed to suit the wasp ' s purposes:'
This "powerful illusion of deliberate design"' is so fundamental a notion and yet so simple that it hardly seems necessary to repeat it. It has been much more fully explored and explained by Richard Dawkins in his wonderful book The Blind Watchmaker:"
Throughout this book I will assume that the greater the degree of complexity there is in a behavior pattern, genetic mechanism, or
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psychological attitude, the more it implies a design for a function.
Just as the complexity of the eye forces us to admit that it is designed to see, so the complexity of sexual attraction implies that it is designed for genetic trade.
In other words, I believe that it is always worth asking the question why. Most of science is the dry business of discovering how the universe works, how the sun shines, or how plants grow.
Most scientists live their lives steeped in how questions, not why questions. But consider for a moment the difference between the question "Why do men fall in love? " and the question "How do men fall in love? " The answer to the second will surely turn out to be merely a matter of plumbing. Men fall in love through the effects of hormones on brain cells and vice versa, or some such physiological effect. One day some scientist will know exactly how the brain of a young man becomes obsessed with the image of a particular young woman, molecule by molecule. But the why question is to me more interesting because the answer gets to the heart of how human nature came to be what it is.
Why has that man fallen in love with that woman? Because she's pretty. Why does pretty matter? Because human beings are a mainly monogamous species and so males are choosy about their mates (as male chimpanzees are not); prettiness is an indication of youth and health, which are indications of fertility: Why does that man care about fertility in his mate? Because if he did not, his genes would be eclipsed by those of men who did. Why does he care about that? He does not, but his genes act as if they do. Those who choose infertile mates leave no descendants. Therefore, everybody is descended from men who preferred fertile women, and every person inherits from those ancestors the same preference.
Why is that man a slave to his genes? He is not: He has free will.
But you just said he 's in love because it is good for his genes: He 's free to ignore the dictates of his genes. Why do his genes want to get together with her genes anyway? Because that 's the only way they can get into the next generation; human beings have two sexes that 'must breed by mixing their genes. Why do human beings have two sexes? Because in mobile animals hermaphrodites are less good HUMAN NATURE