The authors of the study caution that any interpretation of this finding must take into account that the group difference in brain activation between heterosexual men and homosexual men in the amygdala region is not large and that the most robust finding is that both heterosexual and homosexual men used the same areas when they reacted to sexually preferred stimuli. The inactivation of the X chromosome occurs randomly throughout the embryo, resulting in cells that are mosaic with respect to which chromosome is active. He obtained brains from 41 deceased hospital patients. The four variants were also correlated with mood and mental health disorders; major depressive disorder and schizophrenia in men and women, and bipolar disorder in women. Retrieved from " https: This clearly contradicts the hypothesis that homosexual males have a female hypothalamus.
While scientists do not know the exact cause of sexual orientationthey theorize that a combination of genetic, hormonal, and social factors determine it.
The life of the gay gene: from hypothetical genetic marker to social reality.
Neurons of the oSDN show aromatase expression which is also smaller in male-oriented rams versus female-oriented rams, suggesting that sexual orientation is neurologically hard-wired and may be influenced by hormones. These areas of the hypothalamus have not yet been explored in homosexual females nor bisexual males nor females. There is no indication that social environment after birth has an effect on gender identity or sexual orientation. Also, the authors of the study acknowledge that a large number of sexual partners may not lead to greater reproductive success, specifically noting there is an "absence of evidence relating the number of sexual partners and actual reproductive success, either in the present or in our evolutionary past". Another issue is the finding that even monozygotic twins can be different and there is a mechanism which might account for monozygotic twins being discordant for homosexuality.
A study suggests linkage between a mother's genetic make-up and homosexuality of her sons. Simon LeVaytoo, conducted some of these early researches. The "gay uncle hypothesis" posits that people who themselves do not have children may nonetheless increase the prevalence of their family's genes in future generations by providing resources e. Daryl Bema social psychologist at Cornell Universityhas theorized that the influence of biological factors on sexual orientation may be mediated by experiences in childhood. J Pers Soc Psychol.