We Are Our Brains (11 page)

Alfred Kinsey didn't attract any notice when he published his doctoral thesis on gall wasps. But in 1948, when he produced the report
Sexual Behavior in the Human Male
and then, five years later,
Sexual Behavior in the Human Female
, he became a celebrity. He devised the “Kinsey scale,” which went from 0 to 6, 0 signifying exclusively heterosexual
and 6 exclusively homosexual. Being bisexual, he himself would have been classified as a “Kinsey 3.”

A person's position on the scale is determined in the womb by his or her genetic background and the effects of hormones and other substances on the developing brain. Studies of twins and families show that sexual orientation is 50 percent genetically determined, but the genes in question haven't yet been identified. It is curious that a genetic predisposition for homosexuality should persist in populations over the course of evolution, given that this group reproduces so much less. One explanation for why homosexuality persists is that the involved genes don't just increase the likelihood of homosexuality but also promote fertility in the rest of the family. Heterosexual individuals with the same genes produce a larger than average number of offspring, causing the genes to remain in circulation.

Hormones and other chemical substances importantly affect the development of our sexual orientation. Girls with the adrenal gland disorder CAH who are exposed to high testosterone levels in the womb are more likely to become bisexual or homosexual. Between 1939 and 1960, around two million expectant mothers in the United States and Europe were prescribed the synthetic estrogen known as diethylstilbestrol (DES) in the belief that it would prevent miscarriages. (It didn't, in fact, but doctors like to prescribe things, and patients are always keen to be treated.) DES turned out to increase the likelihood of bisexuality and homosexuality in the daughters of women given the drug. Pre-birth exposure to nicotine or amphetamines also increases the likelihood of lesbian daughters.

The more older brothers a boy has, the greater the chance that he will be homosexual. This is due to a mother's immune response to male substances produced by boy babies in the womb, a response that becomes stronger with each pregnancy. Pregnant women suffering from stress are also more likely to give birth to homosexual children, because their raised levels of the stress hormone cortisol affect the production of fetal sex hormones.

Although it's frequently assumed that development after birth also importantly affects our sexual orientation, there's no proof of this whatsoever. Children brought up by lesbians aren't more likely to be homosexual. Nor is there any evidence at all for the misconception that homosexuality is a “lifestyle choice.”

The above-mentioned factors alter the development of the child's brain, particularly the hypothalamus, which is important for sexual orientation. In 1990 Michel Hofman and I found the first brain difference in relation to sexual orientation: The brain's biological clock turned out to be twice as large in homosexual men as in heterosexual men. At the time we were actually looking for something else. I'd previously discovered that Alzheimer's damages the biological clock, which explains why people suffering from this disorder wander around at night and doze during the day (see
chapter 18
). I did some more studies to see if the same applied to other forms of dementia. In the case of AIDS dementia I found that the biological clock was twice as large as normal. Follow-up studies showed that this wasn't caused by AIDS; it was related to homosexuality. In 1991, Simon LeVay reported a second difference in hypothalamic structure between homosexual and heterosexual men, and in 1992 Allen and Gorski found that the structure on top of the hypothalamus that connects the brain's left and right temporal lobes is larger in homosexual men.

Scans have also revealed functional differences in the hypothalamus with regard to sexual orientation. A study by Ivanka Savic of the Stockholm Brain Institute involved pheromones, the scented sex hormones that are given off in sweat and urine. Pheromones influence sexual behavior unconsciously. A male pheromone stimulates activity in the hypothalamus of heterosexual women and homosexual men but doesn't provoke a response in heterosexual men. It seems that male scents don't turn them on. Lesbian women were found to react differently to pheromones than heterosexual women. Savic also showed that heterosexual women and homosexual men had more extensive functional connections between the amygdala
and other brain areas than heterosexual men and homosexual women, proving that brain circuits function differently according to sexual orientation. Functional scanning also showed changes of activity in other brain areas. In the case of heterosexual men and homosexual women, the thalamus and prefrontal cortex responded more strongly to a photograph of a female face, while in the case of homosexual men and heterosexual women these structures responded more strongly to a male face. In other words, sexual orientation is determined by many structural and functional differences in the brain, all of which develop in the womb during the second half of pregnancy. They aren't caused by the behavior of dominant mothers, who are the traditional scapegoats in this context. Just for the record, I made a habit over the years of asking the medical students I taught (250 at a time) which of them did
not
have a dominant mother. No one ever raised their hand.

Toward the end of George W. Bush's presidency, an “ex-gay movement” that regarded homosexuality as a curable disease gained momentum. Hundreds of clinics and therapists jumped on the bandwagon, and it was claimed (but not proven) that 30 percent of those who went into therapy were cured. At such clinics, you received two weeks of “treatment” for $2,500 or six weeks of treatment for $6,000. The therapists were often homosexual themselves
but claimed to have been turned into family men after therapy. A countermovement with the slogan “It's OK to be gay” claimed that the therapies involved conditioning based on stigma and shame as well as discrimination against homosexuals. In 2009 an annihilating report by the American Psychological Association (APA) confirmed that the treatments were causing a rash of suicides among patients. The report concluded that therapy to change homosexuals into heterosexuals didn't work and that the association's 150,000 members should stop offering it to their clients. The report stated that the best such therapy could do was to teach people to ignore their feelings and to suppress homosexual inclinations. It went on to confirm that the therapy could cause depression and even lead to suicide.

All the research indicates that our sexual orientation is programmed in the brain before birth, determining it for the rest of our lives (see earlier in this chapter). Many structural and functional differences have now been found between the brains of homosexual and heterosexual men that must occur early on in development and can no longer be changed by the post-birth environment. Even an upbringing in a British boarding school apparently doesn't make you more likely to be homosexual in adulthood. Initially I thought that “curing” homosexuals was a typical aberration of the Christian community in America, but I was amazed to find that it goes on in the Netherlands too. The Pentecostal Church holds meetings whose prayers can allegedly “cure” you simultaneously of homosexuality and HIV infections, after which you're married off to a woman from the Pentecostal community. It's not just misleading but also potentially life-threatening to make seropositive individuals think that they've been cured in this way and no longer need to take any medication.

The outmoded notion that we're free to choose our sexual orientation and that homosexuality is therefore a wrong choice is still causing a lot of misery. The stories I heard when I gave a lecture to ContrariO, a Christian gay association, showed that homosexuals brought up in the Dutch Reformed Church tradition can still struggle
terribly with their sexual orientation. Indeed, until recently, homosexuality was still regarded as a disease by the medical community. Only in 1992 was it removed from the ICD-10 (International Classification of Diseases). Before that time, doctors had striven to “cure” men of their homosexuality.

The idea that our social environment shapes our sexual orientation has led to mass persecution. The Nazi notion, as expressed by Hitler himself, that homosexuality was as infectious as the plague led to the unimaginable in Germany: first voluntary castrations, then compulsory castrations, and finally the systematic murder of homosexuals in concentration camps.

An important argument against the idea that homosexuality is a “lifestyle choice” or caused by environmental factors is the demonstrable impossibility of ridding people of their homosexuality. Every conceivable thing that could be devised has been tried: hormone treatments, castration, and treatments that influence libido rather than sexual orientation. Electroshock therapies have been tried, as well as epileptic insults. Prison sentences have proved equally ineffectual, as seen in the sad case of Oscar Wilde. Testicular transplants have been carried out, leading to a “success story” in which a homosexual man pinched the nurse's bottom after the operation. Psychoanalysis has also been tried, of course, as well as giving homosexuals apomorphine, a drug that induces nausea, in combination with homoerotic images, as a form of aversion therapy. The story goes that this didn't diminish the men's erotic desires; its only effect was to make them start vomiting as soon as the therapist entered the room. Brain operations have also been performed on homosexual prisoners with a view to reducing their sentences if the treatment proved effective. Naturally, the men all said that it was effective.

Since none of these approaches has led to a well-documented change of sexual orientation, there can be little doubt that by adulthood our sexual orientation has been determined and can no longer be influenced. If churches were finally to accept this fact, the lives of
many of their young members and clergy would be a great deal happier.

Homosexual behavior has now been observed in around 1,500 animal species, from insects to mammals. The male penguin couple Roy and Silo in New York's Central Park Zoo are a famous example. They copulated, built a nest together, took care of an egg that a kindly keeper gave them (hatching it out after thirty-four days), and together looked after the baby. If a female rat develops alongside a male rat in the womb, thus being exposed to more testosterone during early development, it will mount other female rats. Two percent of oystercatchers, a monogamous bird species, form a trio of two females and a male, after which all three guard the same nest. A trio of this kind produces more offspring than a conventional pair, because they are better able to look after and protect the nest.

Behavioral scientists have also shown that homosexual behavior in animals is often used to make peace with enemies or obtain the help of others against possible attackers. Primatologist Frans de Waal has found bonobos to be completely bisexual, a perfect 3 in the Kinsey scale. Where possible, bonobos solve problems in the group by sexual means, through both heterosexual and homosexual behavior. De Waal has found that same-sex practices are displayed by other primates, too, like macaque monkeys, in addition to bull elephants (who mount each other), giraffes (“necking”), swans (greeting ceremonies), and whales (mutual caressing). He classifies such behavior as examples of bisexuality rather than homosexuality, since it only manifests itself in certain periods. However, a preference for same-sex copulation has been reported in a bird in the swamps of New Zealand, a female antelope in Uganda, and cows. Lesbian seagulls have been found in Southern California, jointly incubating a double clutch of eggs. These female gulls copulated with each other as a
pair. However, this proved to be not spontaneous behavior but a byproduct of environmental pollution with DDT, leading to sterility among male seagulls and an excess of females, who formed lesbian couples (see also endocrine disruptors,
chapter 2
). A few male seagulls must of course have escaped the DDT and had the time of their lives inseminating all of the females at least once, but apparently the ladies had no further need of them. In an albatross colony on a Hawaiian island with an excessive number of females, the females would pair up annually to preen each other, join in ritual mating dances, and guard each other. Together they would hatch out a single egg each year, taking turns to sit on the nest. No male came near them after insemination.

According to Frans de Waal,
exclusive
focus on members of the same sex, as shown among humans, is rare if not absent in the animal kingdom. I don't agree with him. In Montana, Anne Perkins discovered that 10 percent of the rams intended for breeding weren't mounting ewes. They were referred to as “lazy.” But out in the meadow they were anything but lazy, as they enthusiastically mounted other males. Some rams even took turns mounting each other. Perkins discovered chemical differences in the hypothalami of these rams that indicated altered interaction between hormones and brain cells. Structural differences were also found in the hypothalami of these homosexual rams just like the ones that we and other researchers described in the case of humans. Of course homosexuality is a natural variation.