The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [126]
Among birds, it is usually only the male that sings. A zebra finch will not sing unless there is sufficient testosterone in its blood. With testosterone, the special song-producing part of its brain grows larger and the bird begins to sing. Even a female zebra finch will sing, so long as she has been exposed to testosterone early in life and as an adult. In other words, testosterone primes the young zebra finch’s brain to be responsive later in life to testosterone again and so develop the tendency to sing. In so far as a zebra finch can be said to have a mind, the hormone is a mind-altering drug.
Much the same applies to human beings. Here the evidence comes from a series of natural and unnatural experiments. Nature has left some men and some women with abnormal hormonal doses, and in the 1950s doctors did the same by injecting some pregnant women with certain hormones. Women with a condition known as Turner’s syndrome, who are born without ovaries, have even less testosterone in their blood than women who have ovaries (ovaries produce some testosterone, though not as much as testicles do). They are exaggeratedly feminine in their behaviour, with typically a special interest in babies, clothes, house-keeping and romantic stories. Men with less than usual testosterone in their blood as adults – eunuchs, for example – are noted for their femininity of appearance and attitude. Men exposed to less than usual testosterone as embryos – for example, the sons of diabetic women who took female hormones during pregnancy – are shy, unassertive and effeminate. Men with too much testosterone are pugnacious. Women whose mothers were injected with progesterone in the 1950s (to avert miscarriage) later described themselves as having been tomboys when young; progesterone is not unlike testosterone in its effects. Girls who were born with an unusual condition called either adrenogenital syndrome or congenital adrenal hyperplasia are equally tomboyish. The effect of this disorder is to cause the adrenal gland, near the kidney, to produce a hormone that acts like testosterone, instead of cortisol, its usual product.15
Somewhat like the zebra finches, there are two periods when testosterone levels rise in male children: in the womb from about six weeks after conception, and at puberty. As Anne Moir and David Jessel put it in a recent book, Brain Sex, the first pulse of hormone exposes the photographic negative; the second develops it.16 This is a crucial difference from the way the hormone affects the body. The body is masculinized by testosterone from the testicles at puberty, whatever its womb experience. But not the mind. The mind is immune to testosterone unless it was exposed to a sufficient concentration (relative to female hormones) in the womb. It would be easy to engineer a society with no sex difference in attitude between men and women. Inject all pregnant women with the right dose of hormones and the result would be men and women with normal bodies, but identical feminine brains. War, rape, boxing, motor racing, pornography, beer and hamburgers would soon be distant memories. A feminist paradise would have arrived.
Sugar and Spice
The effect of this double-barrelled burst of testosterone on the male brain is dramatic. The first dose produces a baby that is mentally different from a girl baby from its first day on the planet. Baby girls are more interested in smiling, communicating and in people; boys in action and things. Shown cluttered pictures, boys select objects, girls people. Boys are instantly obsessed with dismantling, assembling, destroying, possessing and coveting things. Girls are fascinated by people and treat their toys as surrogate people. Hence, to suit their mentalities,