Lesbian, Gay, and Bisexual Youth

Origins of Sexual Orientation

Beliefs about the origins of sexual orientation underlie whether individuals and institutions interpret homosexuality as a natural variation of development or as psychopathology and moral failure. Early psychoanalytic perspectives of homosexuality hold that humans are inherently heterosexual and that homosexuality develops in childhood from improper gender socialization, identification with the opposite-sex parent, alienation from the same-sex parent, or other family system characteristics. Although some sources, usually affiliated with conservative Evangelical or Roman Catholic organizations, still claim that homosexuality develops in this way and is amenable to change through therapy, mainstream psychology and medicine repudiate these views.

Reliable research has never upheld purely psychogenic theories of homosexuality and has specifically refuted their conclusion that homosexuality necessarily connects with psychopathology. Indeed, empirical evidence only supports theories attributing part or all of the cause of variation in sexual orientation to biology. There are, however, many biological and partially biological theories, and research has not demonstrated any of them to be the singular explanation for all variation in sexual orientation. A more reasonable position acknowledges differential developmental trajectories, implying that multiple combinations of factors at multiple life stages create sexual orientation.

Investigations have found genes, brain anatomy, and levels of sex hormones present in the womb with the developing fetus to contribute to variation in sexual orientation. Twin studies find that monozygotic twins are more often of the same sexual orientation than dizygotic twins, implying a genetic component to sexual orientation differences. Human genome research found a possible genetic marker for male homosexuality, but another study failed to replicate this. Rather than directly coding for homosexuality, genes may rather influence sex hormone levels in the womb, which determine degrees of masculinization and feminization of the brain during prenatal development. Experiments on sheep and rats have demonstrated that manipulating prenatal sex hormone levels causes significant differences in sexual orientation, but these findings have not, for obvious reasons, been replicated with humans.

Further corroborating the explanatory role of sex hormones, likelihood of having same-sex attractions increases with every older brother a man has. An explanation for this finding is that repeated exposure of the mother to certain male-specific antigens causes her body to produce antibodies to them, which enter the fetus's bloodstream and interfere with masculinization of the brain. In further support of biological explanations, studies have demonstrated brain anatomy differences via PET scans, postmortem analysis of brain tissue, and paper-and-pencil tasks that demonstrate differences in processing. Same-sex attracted individuals often also exhibit sex-atypicality in handedness, fingerprints, finger length, and reflexive eye blinking.

The preponderance of the evidence points to a mismatch between brain gender and biological sex. This explains why sex-atypicality in childhood is related to later same-sex attractions, and why the correspondence is not one-to-one: brains can be masculine or feminine or in between with respect to several different characteristics, and sexual orientation is only one of them. Biological differences cannot, however, completely explain variation in sexual orientation. Attractions sometimes change over a matter of years, long after puberty. Females are more likely than males to exhibit this “sexual fluidity.” Although an easy answer does not yet exist to the question of how sexual orientation develops, the biological evidence is clear that some individuals are naturally or inherently sex-atypical and/or same-sex attracted, these differences are not linked to mental or physical health problems, and to the extent that they are biologically “hard-wired,” no amount of therapy will change them.

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