Genetic factors influencing sexual orientation in men

Материалы по практической и теоретической психологии и психиатрии.

Genetic factors influencing sexual orientation in men

Сообщение Amortelle – 3 июля 2008, 18:57

A new study by Francesca Iemmola and Andrea Camperio Ciani has recently appeared on-line ahead of print in the Archives of Sexual Behavior:

New Evidence of Genetic Factors Influencing Sexual Orientation in Men: Female Fecundity Increase in the Maternal Line - DOI 10.1007/s10508-008-9381-6

Here is the abstract:
“There is a long-standing debate on the role of genetic factors influencing homosexuality because the presence of these factors contradicts the Darwinian prediction according to which natural selection should progressively eliminate the factors that reduce individual fecundity and fitness. Recently, however, Camperio Ciani, Corna, and Capiluppi (Proceedings of the Royal Society of London, Series B: Biological Sciences, 271, 2217–2221, 2004), comparing the family trees of homosexuals with heterosexuals, reported a significant increase in fecundity in the females related to the homosexual probands from the maternal line but not in those related from the paternal one. This suggested that genetic factors that are partly linked to the X-chromosome and that influence homosexual orientation in males are not selected against because they increase fecundity in female carriers, thus offering a solution to the Darwinian paradox and an explanation of why natural selection does not progressively eliminate homosexuals. Since then, new data have emerged suggesting not only an increase in maternal fecundity but also larger paternal family sizes for homosexuals. These results are partly conflicting and indicate the need for a replication on a wider sample with a larger geographic distribution. This study examined the family trees of 250 male probands, of which 152 were homosexuals. The results confirmed the study of Camperio Ciani et al. (2004). We observed a significant fecundity increase even in primiparous mothers, which was not evident in the previous study. No evidence of increased paternal fecundity was found; thus, our data confirmed a sexually antagonistic inheritance partly linked to the X-chromosome that promotes fecundity in females and a homosexual sexual orientation in males.”

И о том же самом по-русски: http://www.gazeta.ru/science/2008/06/18_a_2758092.shtml
Amortelle
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Сообщение Индиго – 4 июля 2008, 1:47

Давай сюда добавим еще одну статью по теме:

http://healthyfuturelife.wordpress.com/ ... -behavior/

MONDAY, June 30 (HealthDay News) — Genetics and random environmental factors each play a major role in determining both gay and heterosexual behavior, say British and Swedish researchers.

“This study puts cold water on any concerns that we are looking for a single ‘gay gene’ or a single environmental variable which could be used to ’select out’ homosexuality — the factors which influence sexual orientation are complex. And we are not simply talking about homosexuality here — heterosexual behavior is also influenced by a mixture of genetic and environmental factors,” study co-author Dr. Qazi Rahman, a leading scientist on human sexual orientation, said in a prepared statement.

Environmental factors are specific to an individual and may include biological processes such as different hormone exposure in the womb, the researchers noted.


The researchers studied more than 3,800 same-gender twin pairs, ages 20 to 47, in Sweden. The twins were asked about the total numbers of opposite sex and same sex partners they had ever had.

“Overall, genetics accounted for around 35 percent of the differences between men in homosexual behavior and other individual-specific environmental factors (that is, not societal attitudes, family or parenting which are shared be twins) accounted for around 64 percent. In other words, men become gay or straight because of different developmental pathways, not just one pathway,” Rahman said.

Among the female twins, genetics explained about 18 percent of the variation in sexual orientation, non-shared environmental factors 64 percent, and family environment 16 percent.

It’s important to note that heredity and shared environment had roughly the same influence in women, while shared environment had virtually no impact on men’s sexual behavior, the researchers said.

The study, which was published in the journal Archives of Sexual Behavior, shows that while genetic factors are important, non-shared environmental factors are dominant in determining sexual orientation.

“This study is not without its limitations — we used a behavioral measure of sexual orientation which might be okay to use for men (men’s psychological orientation, sexual behavior, and sexual responses are highly related) but less so for women (who show a clearer separation between these elements of sexuality),” Rahman noted. “Despite this, our study provides the most unbiased estimates presented so far of genetic and non-genetic contributions to sexual orientation.”
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