Tag Archives: science

Homosexuality; Nature vs. Nurture

10 Mar

Whilst the American Psychological Association (APA) have changed their original classification of homosexuality from being a mental illness in 1975, it was only in 1994 that the APA put out a statement saying “…homosexuality is neither a mental illness nor a moral depravity. It is the way a portion of the population expresses human love and sexuality” (American Psychological Association, 2010). Today they claim that being homosexual is not a choice and that “…it emerges from most people in early adolescence with no prior sexual experience” (APA, 2010). There are many arguments about whether homosexuality is a consequence of a person’s upbringing, or genetics.

In 1990, Swaab & Hofman discovered that the hypothalamus in homosexual males brains differed to that in a heterosexual’s brain. Other studies have also found this to be true, suggesting that homosexuality is genetic. Twin studies by Bailey and Pillard (1991), discovered that if one identical twin was homosexual, there was a 52% chance of the other one being so too, the chance was lowered to 22% for non- identical twins and only 11% for non- related adopted brothers. This research also suggests that homosexuality is genetic, supporting the nature side of the debate. Then in 1993, Hamer discovered the ‘gay gene’; the X-Chromosome called Xq28. This Chromosome was found to have certain markers in 64% of both homosexual brothers.

Despite sufficient evidence for the nature side of the debate, sociobehaviourists do not agree, claiming that homosexuality is caused by environmental factors, especially in childhood. In 1999, Wickelgren questioned Hamer’s study and concluded that the link is too weak between the Xq28 Chromosome and homosexuality. Parenting has been suggested to cause some people to be homosexual. Factors such as whether boys were allowed to play with dolls, or treated like a ‘sissy’ girl, have been linked to homosexuality, as well as child abuse (Nicolosi, 2002). If someone was to take the view of a Tabula Rasa, a blank slate, then it could be argued that upbringing must be the cause of homosexuality.

[Graph above retrieved from: Satinova, J. (1995). The Complex Interaction Of Genes And Environment: A Model For Homosexuality. Collected Papers from the NARTH Annual Conference.]

The above graph shows some possible environmental effects which could contribute to homosexuality and the percentage of relevant genes inherited. It suggests that both nature and nurture contribute, but neither are essential.

The nature side of thedebate has much more scientific and reliable research conducted in favor of it. Many ‘nurture’ factors could contribute to homosexuality developing, but it is likely that the persons susceptibility to be homosexual is due to genetics and ‘nature’. Whilst genetics may not always be the cause, there is no doubt that the nature side of the debate is a valid theory.



Bailey, J. M., & Pillard, R. C. (1991). Genetic Study of Male Sexual Orientation. Arch Gen Psychiatry, 48(12), 1089-1096.

Hamer, D. H., Hu, S., Magnuson, V. L., Hu, N., & Pattatucci, A. M. (1993). A linkage between DNA markers on the X chromosome and male sexual orientation. Science, 261(5119), 321- 327. DOI: 10.1126/science.8332896

Nicolosi, J., & Nicolosi, L. A. (2002). A Parent’s Guide to Preventing Homosexuality. Intervarsity Press.

Publication Manual of the American Psychological Association, 6th ed (2010). Washington, DC: American Psychological Association.

Swaab, D. F., & Hofman, M. A. (1990). An enlarged suprachiasmatic nucleus in homosexual men. Brain Research, 537 (1-2), 141- 14. http://dx.doi.org/10.1016/0006-8993(90)90350-K

Wickelgren, I. (1999). Discovery of ‘Gay Gene’ Questioned. Science, 248(5414), 571. DOI: 10.1126/science.284.5414.571