It is difficult to critically evaluate both sides of the quandary regarding the origins of sexual orientation if it is framed as either biological or “a choice,” as the argument often tends to arise in media and emotional debates. If, however, the latter position is reframed as environmental, then this becomes an issue not of right or wrong, but of nature versus nurture. Is sexual preference derived from biological processes or does it come via our surroundings? When the debate is viewed in this manner, it becomes an issue of what is shaping our orientation, and the course of its development. We will make greater strides in understanding sexual orientation and how it is formed if we do not fight between what is right and wrong for a human to do or be, but rather, we look through a lens of curious ambivalence, searching for truth through a dearth of perspectives. From evolution and societal structures to minuscule, powerful genes and individual experiences, sexual behavior is a rich kaleidoscope if we can be open to viewing more than our own contributing pigments.
There are many biological theories, studies, and data that have been put forth about the basis for sexual orientation. However, biology is a wide field, which may include many factors that are not directly connected to the biological makeup of a single person (for example, prenatal hormones fit under biology, but they are an external influencing factor rather than a genetic component of the child). For the sake of simplicity, I will focus on specifically genetic arguments.
Firstly, there are studies that have shown similarities in the chromosomal structures of homosexual males. Hamer, Hu, Magnuson, Hu, & Pattatucci, found in a 1993 analysis of over 100 families of homosexual men found heightened same-sex orientation rates in male cousins and maternal uncles of the subjects, but not on the paternal side, suggesting potential sex-linked transmission (p. 321). A smaller sample of 40 families containing two gay brothers showed the brothers to have a high instance of the same DNA markers on a region of the long arm of the sex chromosome, Xq28 (Hamer et al., 1990, p. 321). This X-specific marker may be X-linked, a genetic distinction that would pass down through the maternal line and which can explain at least one subtype of homosexuality genetically, according to the results of this study (Hamer et al., 1990, p. 323).
Another biological explanation of the formation of sexual orientation is also related to family. According to an extensive review paper from 1998 by Pillard and Bailey, one familial study found much higher rates of nonheterosexual (2-6 on the Kinsey scale) men who had another nonheterosexual brother than the rates among those of heterosexual (0-1 on the Kinsey scale) brothers with a nonheterosexual brother (p. 4); this study combined with other like studies gave a rate that was 2-5 times higher, and nonheterosexual women seem to have more nonheterosexual sisters than heterosexual women at more variable rates (p. 5). Several twin studies as well have found that between monozygotic, dizygotic, and adopted siblings, monozygotic twins had the highest concordant percentage of nonheterosexual orientation; in one study of male siblings reared in the same household, 52% of sampled monozygotic twins were concordant for nonheterosexuality, dizygotic twins showed a more modest concordance (22%), and even fewer adopted siblings shared nonheterosexual orientation (11%) (Pillard & Bailey, 1998, p. 5). This suggests that genetics play a significant factor in the formation of sexual orientation independent of environment.
Environmental theories of sexual orientation are also numerous, but have fallen out of favor in the past few years, as sexual orientation is popularly polarized to be either innate and unchangeable, or a conscious decision. Still, there are many differences in the way individuals develop based on their personal experiences, the way that they are raised, and the culture in which they grow up, so many theorists are still searching for the impact these factors have on sexuality.
One theory that showed up consistently in my research on the environmental side of the argument is called “Exotic Becomes Erotic.” This developmental theory by Bem, published in 1996, does not exclude biological variables, but rather places them in a place of differing importance: these variables help to code for childhood temperaments (p. 320). These temperaments predispose the child to enjoy certain types of activities, which could be male-typical (like rough-housing and competitive sports), or female-typical (such as socializing or hopscotch); this leads gender-conforming children to feel unlike their opposite-sex peers, and gender-nonconforming children to feel unlike their same-sex peers (Bem, 1996, p. 331). In both cases, perception of dissimilar peers as exotic produces high nonspecific autonomic arousal, which later in life will transform into attraction even if in childhood it is not consciously felt (Bem, 1996, p. 331). According to Bem (1996), other studies have shown gender-nonconformity in childhood to be a strong predictor of sexual orientation development later in life, with gay men for instance much more likely than straight men to report that they did not enjoy male-type activities and mainly had female friends as children (p. 331). The course of this theory may be altered or supplanted by conditioning or social learning, which can happen as orientation shifts over the course of life; some bisexual respondents, for example, added same-sex erotic attraction to their established heterosexuality after adolescence (Bem, 1996, p. 330).
Another study in favor of the environmental side of this debate is an enormous correlational analysis study compiled from a national cohort of 2 million Danes aged 18-49 over the course of at least thirty years (heterosexual marriage studied since 1970, and homosexual marriage studied from the time it became legal in Denmark, 1989) (Frisch & Hviid, 2006, p. 533). This study was conducted in order to examine childhood family correlates of homosexual and heterosexual marriage, and provides prospective, population-based evidence that childhood family experiences have substantial impact on homosexual and heterosexual human mating behaviors (Frisch & Hviid, 2006, p. 533). Rates of marriage were found to be different across the “urban-rural gradient,” with people born in small towns having much higher rates of heterosexual marriage than the rates in cities, and people born in cities having higher rates of homosexual marriage than the rates in small towns (Frisch & Hviid, 2006, p. 543). Parental ages at childbirth were linked inversely to the tendency to marry heterosexually, while homosexual marriage tendency increased with parental age; parental stability showed significant correlations as well, with heterosexual marriage rates being consistently reduced when there were unstable parental relationships (unknown father, divorce, et cetera), whereas homosexual marriage rates were positively linked to unstable parental relationships (Frisch & Hviid, 2006, p. 545).
When I began researching both sides of this debate, biological sources proliferated. It was much more difficult to find solid environmental arguments. However, once I found several of the latter, they seemed to stand up better under scrutiny. One reason for this is that both of the biological arguments hold true mainly for men, and both focus on the niche of men with brothers. Although their findings of genetic markers and heritable linkages are compelling and warrant further research, the results are curious more than they are conclusive, with small sample sizes and still not much more than correlational results. It could be argued that the Denmark study shows correlates for marriage, not orientation. While technically true, sexual orientation and marriage are both labels we give to a set of intimate behaviors that fit into our defined societal norms. This study still does not offer causation (and it does not claim to), but has a power of huge numbers of respondents and is also somewhat longitudinal, offering both breadth and depth. The Bem theory offers parsimony that follows the trajectory of child development into sexuality. He also does not claim that his theory is a hard and fast rule, but it follows the model of our gender divided society, and he brings in research from other studies to support it. Sexual orientation likely has essential biological and environmental components that combine into our interactions and attractions to other people. From what I read, the environmental position has a solid toehold if more research can be done and can be prolific if it combines with the wealth of data that biology is increasingly presenting.
Bem, D. (1996). Exotic becomes erotic: A developmental theory of sexual orientation. Psychological Review, 103(2), 320-335.
Frisch, M., & Hviid, A. (2006). Childhood family correlates of heterosexual and homosexual marriages: a national cohort study of two million Danes. Archives of Sexual Behavior, 35(5), 533-547.
Hamer, D., Hu, S., Magnuson, V., Hu, N., & Pattatucci, A. (1993). A linkage between DNA markers on the X chromosome and male sexual orientation. Science, 261(5119), 321- 327.
Pillard, R., & Bailey, J. (1998). Human sexual orientation has a heritable component. Human Biology, 70(2), 1-11.