Women After All: Sex, Evolution, and the End of Male Supremacy by Melvin Konner Read Free Book Online Page A

doing its thing, if the androgens can’t have their effect, there is no maleness at all, not in body and not in mind.
    But what about the variety within the typical range, people who have nothing unusual in their chromosomes and no ambiguity in their genitals? Yet they may be men who love other men but also go hunting, boys who dress up like girls but have crushes only on real girls, girls who beat up boys and who want to grow up to be sexy actresses, women and men who have always been sexually attracted to both women and men, men who love flower arranging and women’s fashions but are intensely heterosexual, women kickboxers who puton lipstick and bat their eyelashes at a man they meet at a dance, and a thousand other combinations and variations that no one can predict from any external characteristics or physiological measurements.
    What causes these variations remains mysterious, but evidence strongly suggests that a lot of the causes lie in as yet unknown genes. Why would I confidently say that if the genes remain hidden?
    Although locating a gene and tracing the chemical pathway from it to the physiology—nerves and hormones—is now the gold standard for claiming genetic effects, it is not the only standard. For well over a century, scientists have realized that identical twins (who share almost the same genes) are more similar in many measurable ways than same-sex fraternal twins (who have only as much genetic relatedness as ordinary brothers or ordinary sisters). This is true for height, weight, susceptibility to many specific illnesses, longevity, muscle strength, body fat, nearsightedness, hearing loss in middle age, skin complexion, hair and eye color, nose shape, cheekbone prominence, and many other physical features.
    It is also true of most behavioral traits and psychological measures, including IQ, verbal, mathematical, and musical ability, athleticism, extraversion or introversion, nervousness, aggressiveness, susceptibility to many specific mental and emotional illnesses, religiosity, political conservatism or liberalism, and many others. We can argue about this or that method of measurement, we can point out that genes interact with one another and that this complicates the analysis, we can recognize the considerable power of the environment, including the culture, but in the twenty-first century we can no longer ignore the fact that identical twins are more similar than nonidentical twins, even if the identicals were raised in different, separate environments. There is a number for something called “heritability” that is sometimes calculated from the degree of correspondence between the twins of the different types. Arguments rage over the way this calculation can or should be done.
    I don’t think it matters, because that number isn’t what matters.What matters is how similar the twins are. If one of a pair of twins develops schizophrenia, an identical twin will have a fifty-fifty or greater chance of getting the same disease, while if the twin is not identical, the risk will be much lower. In the case of schizophrenia, the difference remains very great even if the twins have been reared apart. This is true of many illnesses, mental and physical, and it is true of many traits, including height, verbal ability, moodiness, and aggression. We don’t need to know the “heritability” number, or even care whether or not it is worth the calculation; we just need to know that identical twins are a lot more similar (even if they grow up in different environments) than same-sex nonidentical twins—that’s how we know that the thing we measured has been influenced significantly by genes.
    Twin studies are a good way to find this out, but there are other ways. We have been aware for decades that the biological children of people with schizophrenia who are adopted away from their parents in the first month of life are much more likely to become schizophrenic than the biological children of