Biological factors in respect to gender identity and sexual orientation

Suppose that you are biologically and physically a male, but on the inside, you feel as though you are female. What could possibly cause this unorthodox feeling? You find the answer from none other than the brain. The human brain plays a major role in sexual differentiation in relation to gender identity as well as sexual orientation. These sex differences are expressed in human behavior following the first few days of birth until adulthood. For example, when infants are 3-8 months old, girls tend to choose to play with dolls while boys prefer toy cars and balls; however, there are individuals who do not identify with these normal feelings and behaviors. In the article, "Sexual differentiation of the human brain,” biological factors, such as mutations and structural and functional brain differences, can result in conflicting gender identities and sexual orientations.

Sexual differentiation of the genitals takes place at a much earlier state than sexual differentiation of the brain. Once the differentiation of sexual organs is established, sexual differentiation of the brain occurs. This process involves a direct effect of testosterone on the developing human brain. Individuals who are present to their standard levels of testosterone in the womb will develop normally and healthy. Sometimes, however, mutations can occur within the womb. For example, girls who are exposed to high testosterone levels in the womb are more likely to choose boys as playmates and display certain typical male personality characteristics. Furthermore, a male fetus that does not successfully allow the transformation of testosterone into dihydrotestosterone (a male sex hormone) will result in a ‘girl’ with a large clitoris. These children are typically raised as girls, but the occurrence of puberty raises many questions for how the children should then continue to live. Because testosterone levels increase, some of these children will choose to live as heterosexual males. This is important in the establishment of gender identity. If an individual is biologically a female, is she obligated to live her life as a female or should she decide based on how she feels inside? Thus, testosterone levels prove to play a crucial role during pregnancy in the development of such sex differences in behavior.

Sexual orientation refers to the gender to which a person is attracted. Much like gender identity, sexual orientation is determined during early development as a result of genetics. Both structural and functional brain differences can cause differences in sexual orientation among individuals. The suprachiasmatic nucleus, a structure within the hypothalamus of the brain, can be attributed to sexual orientation. D.F. Swabb found the suprachiasmatic nucleus to be nearly twice the size in homosexual men as heterosexual men. In his research with laboratory rats and ATD, an aromatase inhibitor, D.F. Swabb was able to support his hypothesis that an increased number of vasopressin neurons found in the suprachiasmatic nucleus of adult homosexual men is strongly correlated with differences among sex hormones and the brain early in development. The X-chromosome is also believed to play a role in sexual orientation, because it encompasses genes involved in sex and reproduction. Hamer and colleagues found linkage between DNA markers on the X chromosome and male sexual orientation. The significance of these functions relates to how individuals identify with people of the same or opposite sexes and can help individuals identify with their sexual orientation. The suprachiasmatic nucleus and X chromosome thus prove to be important elements in respect to sexual orientation.

The causes behind gender identity and sexual orientation have been an increasingly controversial debate. Information based on the findings of D.F. Swabb has shown that differences in gender identity and sexual orientation are a result of biological factors. With understanding of these concepts, individuals may finally be able to assess and understand their own behaviors and feelings.



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