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Behavioral Genetics: Can We Know Too Much?

kcough's picture

Before beginning research on this paper, I was relatively confident that there was a specific gene in our bodies that directly influenced our sexual preference. After all, most people know with much certainty from an early age their sexuality, so there must be some sort of inherent trait that determines it. I turned to a field previously unknown to me, that of Behavioral Genetics, to answer my question of whether or not our sexuality is predetermined. I soon learned that the field of Behavioral Genetics is incredibly controversial, from the way studies are conducted to the ethical and moral issues that inevitably surround almost every topic, homosexuality especially. Indeed, whether or not the field should even exist is occasionally called into question. If we are to discover the origins behind human traits such as homosexuality, or personality, or a high IQ, will this perhaps entice people to alter the traits of a fetus in utero? Are there, perhaps, some questions that are better left unanswered? In an article on the Ethics of Genetic Research, scholars mused that perhaps “Even granting that, in general, knowledge is better than ignorance, not all risks for the sake of knowledge are worth taking” (2). I started to wonder not only if I could answer the question I was asking, but if I even wanted to.

The question of whether or not homosexuality had a biological origin was first raised about a century ago, by Havelock Ellis and Edward Carpenter (6). There are two theories in the field of genetic research on homosexuality. The first is that of the Indirect Effect—being that genes determine character traits and behavior, which in turn affect how we interact with our environment, which affects our sexuality. The Direct Effect suggests that there is a specific gene that shapes sexual preference (2). The first study to emerge with concrete research supporting the Direct Effect was that of Dean Hamer, a molecular geneticist for the Naitonal Cancer Institute, in 1993. Hamer caused a great stir in the scientific community when he announced his discovery of a certain region (which Hamer named Xq28) on one of the X chromosomes (that is, one of the chromosomes passed from a mother to a son) that was shared by 82% of brothers who both identified as homosexual (6). Hamer’s study, while it is one of the most widely publicized and referred to in the field of Behavioral Genetics, is also highly controversial. Hamer studied only men who had “essentially never veered from their preference for men in their sexual fantasties or activities” (6). He did not study men who came out later in life, perhaps after having been married, or bisexual men, and did not look at whether or not the Xq28 code also existed in the heterosexual brothers of the men (8). No one has since been able to duplicate Hamer’s study, however, a similar one conducted by University of Western Ontario’s neurogenetecist George Ebers concluded that the Xq28 region was not consistently shared by homosexual brothers (8). While many studies have been conducted in a comparable manner as to whether or not this ‘gay gene’ is indeed shared, none have been as conclusive as Hamer’s initial claims. Most, in fact, seem to point not to a specific gene but to a number of other biological factors, even possibly birth order. Another widely referenced study by Northwestern University’s Michael Bailey and Boston University’s Richard Pillard in 1991 found that of homosexual males with monozygotic cotwins (that is, identical, those who share all DNA with their twin) 52% (29/56) of the men were both gay. Of those with dizygotic cotwins (fraternal twins who share 50% of their DNA), 22% (12/54) were both gay, and of non-twin brothers (who share 50% of their genes), 11% (6/57) were both gay (4). This seems odd, since one would assume that the numbers for fraternal twins and non-twin brothers should be relatively equal, seeing as how they both share the same percentage of DNA. In short, there seems to be little consistency or conclusive evidence in even the most comprehensive of studies that can point to a particular genetically inherited trait accounting for homosexuality. What then, are we looking for? If it isn’t a gene that influences our sexuality, where does it come from?

A study conducted in 1991 by neurophysiologist Simon LeVay found that the size of brain’s anterior hypothalamus was comparative in homosexual men to that of heterosexual women—about two times smaller than that of heterosexual men (4 & 6). LeVay, however, conducted his research on cadavers, many of whom had died of AIDS, which is thought to change the structure of the brain. He also had no evidence that the women he studied were indeed heterosexual (6). No other decisive studies have been done that support his conclusions. So if it isn’t in our genes, or in our brains, where is it? A study by Blanchard and Kassan in 1996 pointed to the fact that “each additional older brother increases the odds of homosexuality in the next male born by ca. 33%” (3). They thought that mothers become increasingly immune to the antigen H-Y with each childbirth, and that perhaps the absence of H-Y contributes to an individual’s homosexuality (3). Others point to the presence of androgen, a name for different types of hormones that determine sexual characteristics, such as testosterone in men and estrogen in women (4). In essence, there is no one gene or one biological structure that determines whether or not we are gay, and because of the varying environmental factors that must be accounted for in such genetic research, it is almost impossible to even conduct the studies in the first place. Our sexuality is a product of not only our genetics but also our environment, and cannot be pinned on one or the other.

It became clear to me, the more I discovered, that perhaps the question I ought to be answering was not what makes us hetero or homosexual, but what problems would arise from providing a concrete answer to such a question. It seemed at first that supplying society with a biological reason for homosexuality might increase tolerance and make a strong case for gay rights. If homosexuality is inherent, wouldn’t it follow that homosexuals should be afforded the same rights as everyone else, since it is not a choice or a preference but a biological trait? While ideally this would be the case, there is a long history across the world of discrimination based on biological factors such as sex, race, and ethnicity—why would homosexuality be any different? A discovery like this would also imply that homosexuality “can’t be helped,” and even an attitude towards it as such is a form of discrimination. It should not matter whether or not it can be “helped” because this seems to suggest that it is not normal or natural—the exact sentiment that perpetrates and fuels homophobia. We need to learn to tolerate differences be they biological or otherwise, not simply because they are biological.

Another problem with the discovery of a certain “cause” for homosexuality is that it would inevitably produce a question as to whether or not we could change our sexuality before birth. This is a danger with any sort of genetic research seeking to determine explanations for our biological differences. Would we then be tempted to tamper with our genes? Genetically engineer the “perfect” child? Perhaps a homophobic couple would choose to terminate a pregnancy they believed would produce a homosexual child. The Council for Responsible Genetics justly argues that “By seeking a definitive basis of such behavior in genetics, we risk oversimplifying our view of behaviors” (6). Perhaps we have come to a point where we can know “too much.” Science is constantly misinterpreted and manipulated by those wishing to influence the general public, oftentimes with disastrous consequences. People like quick fixes and clear answers to their problems, and often look to science to provide these—when, in reality, science, as we’ve shown, provides only constantly shifting theories based on circumstantial evidence. A council on the Ethics of Genetic Research observed that “…tests can be both developed and well received even if they are based on bad science” (2). This is all too true. Delving too far into the reasons behind our sexuality unleashes moral and ethical issues far too complex to justify potential findings. We should focus instead on promoting tolerance for all peoples, regardless of the origins, biological or otherwise, of their differences.


1. Is There a ‘Gay Gene’? Article in WebMD’s Health & Sex section. <>

March 2005

2. The Ethics of Genetic Research: On Sexual Orientation, first published in Hastings Center Report 1997, by Udo Schuklenk, Edward Stein, Jacinta Kerin, and William Byne


3. Evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity, The Royal Society, by Andrea Camperio-Ciani, Francesca Corna, and Claudio Capiluppi, Published 18 October 2004


4. OMIM Database-PubMed.gove, Sexual Orientation, Male: Gene map locus Xq28


5. The NY Times: Sniffing Out the Gay Gene, by Steven Pinker, May 17th 2005


6. Council for Responsible Genetics: Do Genes Determine Our Sexuality?


7. The Washington Post: In Search of the ‘Gay Gene’ by Jack Lucentini, February 19, 2001


8. The DNA Files: DNA & Behavior: Is Our Fate in Our Genes? By Sophia Kolipoulos, October 2001



Jessica Chang's picture

I agree with you. Knowing

I agree with you. Knowing the exact answer for any controversial question, such as the one you describe in this article, would be become a great issue in our society. However, I do believe that there is no concrete answer for this question. It is possible that our genes may have an influence on person’s sexual preference, but there are a myriad of other factors (environment, educations, hormones, culture, etc.) that can contribute to a person’s sexual preference. Besides, what is “normal”? How do you define “normal”? How can you determine what is normal and what is not? Somehow I feel “normal” is just whatever the majority possesses, and some people in majority would discriminate the people in minority. For instance, most people are born with ten fingers. If somebody is born with more or less than ten fingers, you would consider it as abnormal. So, what if the gay community becomes the majority? Would the gay discrimination still exist? Therefore, I believe no matter what the real answer for these controversial questions is, some people would still come up with some other reasons to discrimination against specific people. So the real question becomes “how to change the people’s discriminations, opinions or attitudes for other people”.

Paul Grobstein's picture

Behavioral genetics: not knowing enough?

Maybe the problem isn't knowing too much but not knowing enough? It sounds like maybe sex/gender is indeed influenced by genes but also influenced by a number of other things (like many other biological phenomena) and displays a lot of variation (like many other biological phenomena). Maybe if we had more observations we'd begin to recognize that variation due to multiple interacting factors is not only a common feature of biological phenomena but a desirable one? And hence stop looking for simple "fixes" to what aren't actually problems?