After reading the negative comments regarding same sex couples being allowed to adopt children, that made me question - where does our sexuality come from? Are people afraid that “straight” children will grow up gay, lesbian, bisexual or transsexual because of their upbringing? Can your surroundings influence your sexuality or is it all determined genetically?

Genes?

A fetus is female by default and becomes male if the gene SRY is present. The dominant gene of the Y chromosome then develops the reproductive tissue into testes and the hormone testosterone moulds the body into a male.

Gay men have a fifth of the amount of children as straight men which could see the gene that favours homosexuality disappear from the population in the future. Following a study, Dr. Bailey believes that the gay gene enhances fertility in other family members, typically gay men have more relatives than straight men, particularly on their mother’s side of the family.

A study by Ray Blanchard and Anthony Bogaert showed that having older brothers increases the likelihood that a male would be gay but it made no difference if they were brought up together, this result suggests that male homosexuality is formed by some event in the womb.

Discover Magazine published an article in 2007, The Real Story on Gay Genes which included the findings on a report by geneticist Dean Hamer who studied 76 pairs of gay brothers and their families, the result found that homosexuality seemed to be inherited through the maternal line.

Brain?

We know that men and women think differently, it seems that men's brains prompt them to seek out a partner for sex whilst a woman's brain is programmed to find the best partner for them and subsequent children, they look for longer term relationships.

In puberty the brain triggers the reproductive systems by releasing gonadotropin which in turn triggers other hormones. More recent studies have led to the belief that the brain is a fully functional sexual organ although different for male and female. Women use the left side of the armydala to organise their memories whilst men use the right.

The male brain is sexually orientated to desire women despite any cultural influence – there are extreme examples of this where baby boy’s have lost their penises during circumcision and then raised as a girl, they still desire a woman partner. “If you can’t make a male attracted to other males by cutting off his penis, how strong could any psychosocial effect be?” Quote from Dr. Bailey, an expert on sexual orientation at Northwestern University.

Men are more straightforward, in experiments with male and female images a man is aroused by a woman if he’s straight and a man if he’s gay, whereas a woman is aroused by both male and female images. Dr. Bailey said following the tests “I’m not even sure females have a sexual orientation. But they have sexual preferences. Women are very picky, and most choose to have sex with men.”

Gay and straight men have the same level of testosterone.

Summary

Our genes have a significant effect on the sexual differentiation of the brain.

Our brain controls the body’s hormone levels of testosterone and estrogen.

Both of the above are formed before birth and therefore suggests that you are born with your sexuality, for men it seems straightforward you either desire women or men and for women we can choose either – neither of these are influenced by our upbringing, environment or culture.