Dear Born Gay,
People who reject the civil rights of homosexuals often believe that sexual orientation is an evil or poor choice. They also believe that homosexuality can be changed or cured. Our scientific understanding of sex chromosomes has changed radically, and rapidly evolved over the last 120 years. Who knows what future genetic discoveries will bring that will change our fixed notions on gender and sex identifications?
Let’s look at chromosomes and brain structure as identifiers or inborn characteristics. An wide range of chromosomal, hormonal balances, and phenotypic variations are involved in the determination of sexual classification. The X and Y chromosome determine a person’s sex. The Y chromosome is specific to males and the X to females.
Humans are born with 46 chromosomes in 23 pairs. Most women are 46XX and most men are 46XY. There are variations and abnormalities; a few births per thousand are born with a single sex chromosome, 45X or 45Y and some with three or more chromosomes, 47XXX, 47XYY, or 47XXY. In humans, sex is determined by the absence or presence of the Y chromosome, which encodes the SRY gene needed to develop testis. The Y chromosome is small and mostly devoid of genes while the X chromosome contains several thousand genes. Graves (1995), Bioessays Apr;17(4):311-20.
Simon LeVay was on the faculty of the Salk Institute in San Diego in 1991 when he found differences in the brain structure between straight and gay men. The difference was in a group of nerve cells called "INAH3," a cell group in the hypothalamus which helps generate our sexual behavior. Other researchers had previously reported that INAH3 was usually larger in men than in women. INAH3 was also larger in straight men than in gay men.
William Byne, a critic who once doubted that INAH3 even existed, eventually verified that INAH3 exists and is generally larger in men than women and that the cause of death (AIDS versus other diseases) does not affect its size. Byne also found that INAH3 contained the same number of nerve cells in the gay and straight men. If confirmed, this finding would suggest that there is no difference between gay and straight men in the earliest phase of brain development, when nerve cells are being generated and assemble into functional groups. Rather, the difference may arise at some later time, when the nerve cells in INAH3 are growing and forming connections.
The findings on INAH3 to date don’t prove a particular theory of sexual orientation as much as they point to ways in which such theories could be tested in the future. Sexual orientation is not something chosen or mutable. It's simply a human variation. These research findings bring hope that we will eventually be able to understand the origins of sexual orientation at the cellular level, possibly as a variation in the human genome. Won’t that simply irk the people who don’t believe in climate change? Research is leaning toward the theory that sexual orientation is inborn and not simply a choice.
picture by: blindfaeth