Nature vs. Nurture
Scientists have yet to unlock the mysteries of sexual orientation, but significant research is underway. Learn about investigations into the biology of sexual orientation.
DeeWho is Dee?
Hi! I’m here to help you explore a fundamental question: What determines sexual orientation — nature or nurture? Scientists have learned the answer begins with an understanding of the two core elements involved: biological sex (the parts we’re born with) and attraction (who we’re drawn to, romantically and physically). In this section, we’ll investigate what else scientists have learned about the roots of sexual orientation. Let’s dig in…
Scientists explore same-sex attraction
Can genetics help explain the origins of same-sex attraction? What other factors are at play? Learn about a variety of scientific approaches and why researchers believe same-sex attraction is a natural variation in human evolution.
Twin studies reveal important clues to the biology of same-sex attraction.
Controversies in science
Scientists face obstacles when it comes to researching the biology of sexual orientation.
Learn more about the role of genetics in shaping same-sex attraction.
Patterns of family member clustering influenced early efforts to identify a gay gene.
Learn about epigenetics and how it relates to research on sexual orientation.
Differences in hormone development have emerged as a key area of research on same-sex attraction for both men and women.
Scientists have discovered that having older brothers increases the odds of a man being gay.
Scientists believe that hormonal differences may influence sexual orientation.
(Adj.) Describes a person who does not experience any form of sexual attraction. People who identify as asexual may or may not experience emotional, physical, or romantic attraction.
(Adj.) Describes the sexual orientation of persons who are emotionally, sexually, and/or romantically attracted to persons of the same sex/gender. While the term is most often used to describe men, it can also be used more broadly to refer to both men and women (i.e., gay man, gay woman, gay people).
Homosexual / Homosexuality
(Noun) A term that describes a primary or exclusive sexual, emotional, and/or romantic attraction to persons of one's own sex/gender. The term is considered outdated by many in the LGBTQ+ community but is still used in some research contexts.
(Adj./Noun) Refers to the sexual orientation of women who are emotionally, sexually, and/or romantically attracted to women.
(Noun) An enduring emotional, romantic, sexual or affectional attraction or non-attraction to other people. People use a variety of labels to describe their sexual orientation. Some of the better-known labels or categories include bisexual, pansexual, asexual, lesbian, gay or straight. Gender identity and sexual orientation are not the same. Transgender and gender non-conforming people may identify with any sexual orientation, and their sexual orientation may or may not change before, during or after gender transition.
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Citations & Sources
Ashley, K. B. (2013). The Science on Sexual Orientation: A Review of the Recent Literature. Journal of Gay and Lesbian Mental Health, 17(2), 175-182. http://dx.doi.org/10.1080/19359705.2013.767179
Bailey, J.M., Vasey, P.L., Diamond, L.M., Breedlove, S.M., Vilan, E. & Epprecht, M. (2016). Sexual orientation, controversy, and science. Psychological Science in the Public Interest, 17(2), 45-101. doi:10.1177/1529100616637616
Blanchard, R. (2001). Fraternal birth order and the maternal immune hypothesis of male homosexuality. Hormones and Behavior, 40(2), 105-14. https://doi.org/10.1006/hbeh.2001.1681
Bogaert, A.F. (2006). Biological versus nonbiological older brothers and men's sexual orientation. Proceedings of the National Academy of Sciences of the United States of America, 103(28), 10771-4.
Burton, N. (2015, September 18). When Homosexuality stopped being a mental disorder. Retrieved from https://www.psychologytoday.com/blog/hide-and-seek/201509/when-homosexuality-stopped-being-mental-disorder
Cartwright, M. (2015, August 3). Where’s the scientific research into how sexual orientation develops in women? Slate. Retrieved from http://www.slate.com/blogs/outward/2015/08/03/sexual_orientation_in_women_why_so_little_scientific_r...
National Human Genome Research Institute (2016, April 1). Epigenomics. Retrieved from https://www.genome.gov/27532724/epigenomics-fact-sheet/
National Geographic. (2009, February 4). National Geographic explains the biology of homosexuality. Retrieved from https://www.youtube.com/watch?v=saO_RFWWVVA
Queen Mary, University of London. (2008, June 30). Homosexual behavior largely shaped by genetics and random environmental factors. Retrieved from www.sciencedaily.com/releases/2008/06/080628205430.htm
Reardon, S. (2015, October 8). Epigenetic 'tags' linked to homosexuality in men. Retrieved from http://www.nature.com/news/epigenetic-tags-linked-to-homosexuality-in-men-1.18530
Rice, W.R., Friberg, U., & Gavrilets, S. (2012). Homosexuality as a consequence of epigenetically canalized sexual development. The Quarterly Review of Biology, 87(4), 343-368. doi:10.1086/668167
Sanders, A.R., Martin, E.R., Beecham, G.W., Guo, S., Dawood, K., Rieger, G., Badner, J., Gershon, E.S., Krishnappa, R.S., Kolundzija, A.B., Duan, J., Gejman, P.J., & Bailey, J.M. (2015). Genome-wide scan demonstrates significant linkage for male sexual orientation. Psychological Medicine, 45(7), 1379-1388. doi:10.1007/s12119-014-9233-6
TEDx Talks. (2016, November 15). Homosexuality: It's about survival - not sex. Retrieved from https://www.youtube.com/watch?v=4Khn_z9FPmU&vl=en
Wolchover, N. (2012, June 11). Why are there gay men? Retrieved from https://www.livescience.com/33987-gay-men.html
Wolchover, N. (2012, June 12). Why are there gay women? Retrieved from https://www.livescience.com/33992-gay-women.html