The Roots of Human Homosexuality

When the western zeitgeist and social norms surrounding homosexuality shifted towards acceptance and equality in the 1990s and early 2000s, biologists increasingly started describing homosexuality in the animal kingdom (Bailey et al., 2016). Of course, the behavior was always there, ready to be observed by the willing scientist. But it was this socio-political shift in thinking about homosexuality that did away with the taboo around the topic. Since then, it has become clear that many species of birds, sea mammals and primates regularly engage in homosexual behavior (Bailey & Zuk, 2009). However, animals are thought to merely show homosexual behavior, whereas humans develop a homosexual orientation (LeVay, 1996). The American Psychological Association defines sexual orientation as ‘an enduring pattern of emotional, romantic and/or sexual attractions to men, women or both sexes’ (APA, 2008). This difference raises the question whether the homosexual orientation of humans is some essential form of human sexology, partly rooted in biology, or whether it mainly arises out of societal and cultural context. In order to find an answer, first a historical analysis of how homosexuality was conceptualized in the western world is described, focusing on antiquity and the Middle ages. Next, findings of cross-cultural studies on homosexuality are discussed. Finally, attention will be devoted to empirical research into important causal factors of  homosexual orientation.

As a first step in finding an answer to this question, it might be worthwhile to look at history. Without a doubt, the perspective of western society on what homosexuality is exactly has been through significant changes. In Greek antiquity, no concept of homosexuality, nor heterosexuality existed. It was not part of sexual discourse, and therefore, people did not conceptualize themselves like that. This is totally different from our times, in which being gay has become a significant factor in someone’s identity. There were many Greek islands, however, in which homosexual behavior was tolerated or even celebrated (Pickett, 2020). But in the social landscape of those times, other aspects of sexuality were salient, such as moderation and status differences between sexual partners. It was perfectly acceptable for a wealthy Greek aristocrat to have sexual intercourse with a male slave, but not with a Greek male of equal status (Pickett, 2020). Similar norms existed in Roman times. 

Thinking about sexuality changed when Europe was embedded in the grand Christian narrative during the Middle Ages (Pickett, 2020). Any sexual behavior outside marriage between a man and a woman was seen as a transgression of divine law. Such a person was a ‘sodomite’ – this term was extended to a person who engaged in homosexual behavior too. The act itself was seen as morally wrong. It was only later that people who engaged in homosexual behavior were conceived as belonging to a specific group of people: people with the desire and intention to only have sex with someone of the same sex, homosexuals. Foucault, a French postmodern philosopher, who himself was gay, thought this switch from behavior to identity or essence of a person helped maintain Western and Christian power structures (Gutting & Oksola, 2018). People could now be seen as abnormal or morally wrong because of who they are, not because of their sexual behavior. Here, a homosexual orientation becomes a matter of social construction. A problem with this perspective is the assumption that people in the past have never fit the current description of homosexuality. In reality, people could still have had the desire to only have sex with same-sex partners, but not acted in accordance with it. This is what the essentialist perspective states, namely that a homosexual orientation is not created, but observed. It is a natural variation of human sexuality, not a social construct. Which perspective is more likely to be true is a difficult question, but it might help to look into the literature about homosexuality in cultures other than the West — and looking for cross-cultural similarities and differences.

Cross-cultural examination of homosexuality with questionnaires has brought forward data that seems to align with the essentialist perspective. It has been found that in many different cultures, a small proportion of the population describe the consistent desire to be romantically or sexually involved only with people of the same sex (Bailey et al., 2016). The percentage of people who report having a homosexual orienation appears to be similar cross-culturally too. For example, when researchers studied sexuality in the non-Western culture of Samoa (Bailey et al., 2016), they concluded that between 1.4 to 4.7% of the population experiences a homosexual orientation. The estimate for U.S. adults is around 3.5%, indicating close resemblance in proportion. Interestingly enough, sexual identity and behavior were found to be far more susceptible to cultural variation, compared to sexual orientation (Bailey et al., 2016). This means that the way people express themselves publicly, seek sexual encounters, and conceptualize their sexual identity is more dependent on place and time period. Sexual orientation seems to be something deeper, because little variance is observed cross-culturally. Taking the social constructionist position on the basis of a historical analysis of western views on homosexuality wouldn’t be accurate, just like it wouldn’t be accurate to say that male inmates have an homosexual orientation because they consistently engage in same-sex encounters while in prison. 

Finally, it is interesting to look at what factors are at play in determining sexual orientation. Empirically, the bulk of evidence points to factors rooted in biology and genetics, much less to the environment and social causes. One of the most influential theories is that of hormonal exposure during prenatal development (Levay, 2012). When gendered brain differentiation happens inside the mother’s womb, gay men are thought to be exposed to less testosterone, which is responsible for masculinization of the brain. A direct study of this effect by means of manipulating the fetal hormonal cocktail wouldn’t be considered morally sound, and for good reason. But there are a number of observable factors that indicate lower levels of prenatal testosterone, like the finger digit ratio for example. This ratio is calculated by dividing the length of the index finger by the length of the ring finger of the same hand (Levay, 2012). There is a strong relationship between this ratio and the level of testosterone.

It is shown cross-culturally that homosexual men score differently on this ratio compared to heterosexual men, supporting the theory that the level of testosterone affects sexual orientation. When levels of testosterone are decreased prenatally in animals, it often induces life long typically female behavior in males and life long typically male behavior in females — indicating a direct link (Levay, 2012). Next to this, the fraternal birth order effect has been described (Levay, 2012): the chance of a man being gay increases with each succesive male his mother has given birth to. This has to do with antibody development on part of the mother in response to male fetal cells entering the bloodstream, which the immune system does not recognize. These antibodies influence the next developing male fetus in the process of brain differentiation, increasing the chance of a homosexual orientation and less masculinization. Additionally, twin studies have led to the conclusion that heritability of homosexuality is about 50% in men and women, meaning that for 50% of the variance in homosexuality among the population, the causes are genetic. The other 50% in variance was almost entirely explained by unshared variance (e.g. prenatal development, specific life events or error). Close to no variance was explained by shared environment (e.g. similar parental treatment of the twins). One last point to consider is the result of surgical reassignment of sex that happened frequently, between the 1960s and 2000s, when newborn boys had malformed penises (Bailey et al., 2016). With the intention to help, physicians decided that these boys should grow up as physical women, and the parents fully accommodated to this new reality. But soon, when these children grew older, it became clear that their sexual orientation did not develop as expected. In the case studies that described sexual orientation of these children, all developed strong attractions to females only. Six out of seven identified as being heterosexual males, despite being raised typically female-gendered. This points to a greater influence of biological determinants for gender and sexual orientation, opposed to socio-cultural forces. 

In the end, it is clear that sexual orientation has a solid basis in biology and genetics. The fact that people in other cultures seem to show the same proportion of people experiencing it only increases the plausibility of a more essentialist viewpoint. It would be a fundamental error to accept non-essentialism by historically analyzing human behavior, social norms and moral rules, which are in constant flux. We should not throw the baby out with the bathwater though, since culture and societal norms definitely influence the way people express and see themselves. Ultimately, sexual orientation in humans seems to run deeper than mere behavior, which sets us apart from the vast majority of animals (LeVay, 1996). But then, our sexual orientation is not something constructed by society, disconnected from biology, which brings us back, a bit closer to the animal world. <<