The Role of Genetics as it Relates to the Sexual Orientation in Men

Researchers have been actively seeking a link between genetics and sexual orientation for many years. Many tests and experiments have been performed yet no one test or experiment has fully succeeded. Some though have created a basis for further research.

Research conducted by Dr. Sandra Witelson, a neuroscientist at the Michael G. DeGroote School of Medicine at McMaster University, along with several colleagues at Sunnybrook Health Centre in Toronto, developed and tested several hypotheses. Studies have shown that a large amount of homosexual men are solely left handed. Dr. Witelson and her colleagues also found that the posterior part of the corpus callosum area of the brain is larger in homosexual men. Through a correlational analysis which included the size of the corpus callosum, test scores on language, visual spatial and finger dexterity, researchers were able to predict sexual orientation in 95 percent of the cases.

According to scientists biological factors aid in the determination of sexual orientation, though it is not clear which factors play a role or how. Some of the factors being considered are prenatal hormones, chromosomes, polygenetic effects and viral influences. Most scientists will tell you that "gay genes" do not exist. Sexual orientation depends on many different genetic, environmental and cultural interactions.

In 1990, Swaab and Hofman reported that "there is a difference in the size of the suprachiasmatic nucleus in the brain between homosexual and heterosexual men". In 1992, Allen and Gorski reported that "there is a difference related to sexual orientation in the size of the anterior commissure area of the brain".

The size of an individuals INAH3(small part of the hypothalamus) has been researched as a determining factor of one's sexuality, but studies conclude no plausible evidence to support the theory.

Studies have shown a higher likelihood of homosexuality in those who have male homosexual blood relatives, though there is no concrete evidence to support this theory.