Weiteres zu Homosexualität und Biologie („Born this way“)

Beim Calgary Herald ist ein interessanter Bericht (aus 2011) zu Homosexualität und Biologie. Die dort vertretene Position:

„Sexual orientation is an aspect of gender that emerges from the prenatal sexual differentiation of the brain,“ says LeVay, who was one of the first researchers in 1991 to connect brain development to sexual orientation. „Whether a person is gay or straight depends in large part on how this process of biological differentiation goes forward, with the lead actors being genes, sex hormones and the brain systems that are influenced by them.“

In fact, an increasing body of research, which LeVay deftly explores in his latest book Gay, Straight and the Reason Why (Oxford University Press, 2011), completely overturns traditional beliefs that homosexuality is either a psychological issue, the result of sexual assault as a child or even a matter of choice.

Soweit nichts neues. Zu Freud führt er an:

in Freud’s case, LeVay says, „He constructed this adventurous story about what happens to sexuality when you’re young children. He thought of homosexuality as arrested development. Those ideas were to dominate in much of the 20th century. So many gay men in the ’60s underwent psychoanalysis with the idea of overcoming their sexuality. there are many sad stories about how traumatic it was.“

In der Tat sind es bei Freud im wesentlichen erfundene Geschichten, die zwischenzeitlich durch die moderne Forschung überholt sind. Den Versuch, Homosexuelle zu heilen hat man inzwischen glücklicherweise größtenteils aufgegeben.

Auch eine interessante Stellungnahme zu der Theorie, dass Mißbrauch Homosexualiät begründet:

Such theories also mesh with the notion that homosexuality is the result of early sexual trauma. According to the Public Health Agency of Canada, there were 2,607 substantiated cases of child sexual abuse in 2008. Actual cases may be higher; between 1998 and 2003, Internet child pornography went up by 900 per cent, says Statistics Canada. So while some lesbians molested as children believe it plays a role in their emerging sexuality, child sex abuse is so common „one would expect more lesbians than straight women to report having been abused,“ LeVay says. „In a study that compared matched pairs of lesbians and straight women, no such difference existed.“

Zur Selbsteinschätzung der Homosexuellen zum Thema inwieweit Wahl etwas mit ihrer Sexualität zu tun hat:

And while a 2004 Los Angeles Times poll of Americans found one-third believe homosexuality is a matter of choice, just four per cent of gay men and 15 per cent of lesbians felt choice had anything to do with it, according to 1994 and 1995 RAND Institute studies.

Also ein äußerst geringer Teil bei den Schwulen und ein immer noch geringer Teil bei den Lesben. Dies könnte darauf zurückzuführen sein, dass bei Frauen eine gewisse Bisexualität häufiger vorzukommen scheint.

Zu den hormonellen Ursachen dann das Folgende:

fact, some neuroscientists and psychologists theorize that sexual orientation has its roots long before a baby is born. In utero, a male fetus is bathed in testosterone, which influences the development of genitals and brain structures that govern things like communication and fight or flight responses.

„In humans, testosterone is the major hormone responsible for sexual differentiation during early development,“ LeVay says. „The brain starts off rather the same way and develops in a more male or female direction under the influence of testosterone, which comes from the developing testes. If testosterone levels during a critical prenatal period are high, the brain is organized in such a way that the person is predisposed to become typically masculine in a variety of gendered traits, including sexual attraction to females. If testosterone levels are low during that same period, the brain is organized in such a way that the person is predisposed to become typically feminine in gendered traits, including sexual attraction to males. Bisexuality might result from intermediate levels of testosterone, although there is little direct evidence bearing on this.“

Also das klassische Schema hormoneller Beeinflussung im Mutterleib

Auch die Ausführungen zu den Zwillingsstudien sind interessant:

Yet there are other factors, too. Family and twin studies examining the role of genes have found that „estimates of the heritability of homosexuality have been quite variable, but range around 30 to 50 per cent for both sexes, which is similar to the heritability estimates for many other psychological traits,“ LeVay says. Yet science has not yet identified a single „gay gene.“ Rather, like psychological traits, sexuality may be influenced by several combinations of „gay genes,“ which would also explain different types of homosexuality, such as „butch“ or „femme“ lesbians as well as some innate characteristics.

Randomness also plays a role. A New York University study that examined identical twins with gay or straight orientation discovered that the lesbian twin had higher levels of testosterone than her heterosexual sister. „In other words, the same biological factor — prenatal testosterone levels — appears to guide the development of sexual orientation in discordant twins (with different sexual orientation) as it does in gay and straight people generally, but in the case of these twins there is no ultimate cause, such as genetic differences. Rather,“ LeVay says, „it is as if a biological coin had been tossed.“

Und zu den verschiedenen Fähigkeiten in Übereinstimmung mit den hormonellen Theorien:

Whether the result of testosterone, genetics or random chance, sexual orientation impacts a whole range of traits. In some instances, researchers say gay men tend to shift toward the feminine in innate characteristics, while lesbians shift toward the masculine.

In studies in Canada, the U.S. and Britain between 1991 and 2007 that examined the ability to tell if complex objects are the same from different angles, straight men outperformed gay men, who performed better than lesbians. Lesbians also beat straight women.

A 1995 study by University of Western Ontario neuroscientists found that gay men were worse at throwing a ball at a target, while lesbians were better than straight women.

While women are generally more verbally fluent than men due to differences in brain structures which are affected by testosterone in utero, British researcher Qazi Rahman’s work discovered lesbians score significantly worse than straight women and about the same as straight men. Gay men do the opposite; they perform as well as straight women and far better than straight men.

Diese Ergebnisse sind bei hormonellen Einflüssen geradezu zu erwarten. Sie fügen sich gut in dieses Schema ein.