Yesterday when I turned on the TV a show called “The Doctors” was on. On the screen were two images of brain scans showing patterns in brain activity between heterosexual males and females. There was quite a difference between the two. Then they showed the brain scan of a homosexual male, whose brain activity was very similar to the heterosexual females. Alas, the Doctors concluded homosexuals are born homosexuals. The brain scans show it as a biological fact!
That very same day while doing research for genetic causes of age longevity I came across an online article that stated that homosexuality was inherited and therefore genetic. That same day, while flipping through my human genetics text I incidentally came across a section about the possibility of homosexuality being inherited. That’s a lot in one day! Needless to say my curiosity was peaked enough by this time to look much further into it. I’ll be honest, I was curious myself. Are homosexuals born homosexuals, or do they become homosexuals? Is it a choice or predetermined by genes? After a lot of research I found that the answer is both yes and no. Like most topics in genetics and biology, the more we come to discover, the more complicated things are. As geneticist and gene therapist Rick Lewis writes, “Homosexuality at a genetic level is hard to explain because the person’s phenotype and genotype are consistent, but physical attraction is towards the same sex.”
But before we can go forward, bad science needs to be weeded out first. There are so many “evidences” used to support and deny genetic causes of homosexuality that are poor, but widely distributed. Thank you mainstream media! The brain is an excellent example. The brain scans shown on the Doctors show do not show proof that homosexuality is genetic or biologically rooted, they only show commonalities in brain activity patterns. They show an effect, not a cause. If those brain scans are evidence of genetic causes then I could just as easily point to a gay man kissing a man, and a woman kissing a man and say “Eureka, similar patterns! Proof homosexuality is genetic!” Also, how large was the sample of men and women, homo and hetero used in the study? Why didn’t we see an image of the lesbian woman’s brain activity patterns? These are all things that need to be considered when presented with such “evidences.” As Dr. Simon LeVay, a neuroscientist and self-proclaimed homosexual himself states, ““The alternative — that the difference resides only in patterns of brain activity — has been ruled out, because sexual orientation remains unchanged after all brain activity has been temporarily halted.”
As far as the factoids I stumbled across online and the text from my human genetics textbook, they spoke of identical twin testing. Testing which proves to be a much more concrete study than just brain activity patterns. Results from a study back in 1993 (one that has been countless times revisited and retested), identical twins are twice as likely to be homosexual than are same-sex fraternal twins. This experiment was conducted by Dean Hamer, a researcher for the National Cancer Institute. He studied 40 pairs of homosexual brothers. He found that X Chromosomes in 33 of the pairs were the same, and concluded that homosexuality is linked to the X chromosome, though the gene responsible itself was never identified. Many studies done afterwards on identical twins provided less optimistic results, but concluded the same: There is a genetic factor for homosexuality.
Back to the brains. There are regions of the brain that are in fact different sizes between homosexual males and heterosexual males. This research was brought to the public by LeVay in 1991. Studying the cadavers of gay and straight men he found an area in the brain called the anterior hypothalamus (called INAH-3) was much smaller in gay men than straight men. A study by William Byne of the Mount Sinai School of Medicine in New York City turned up similar results. Many have used this finding as further evidence that homosexuality is deeply rooted in biological and genetic factors.
William Reiner, a psychiatrist at the University of Oklahoma Health Sciences Center, concludes that there is a genetic factor to gender identity after his experience with sexually deformed children. When children are born with deformities, for example boys with a deformed penis, they are often surgically castrated and raised as girls in an effort to give them a life less painful than being raised as a boy with a deformed penis. Many of these boys never take to being a female despite being treated like one and given estrogen therapy. This lead Reiner to conclude that environment isn’t the cause of our gender identity and therefore it must be genetically determined.
As R. Elizabeth Cornwall, a psychology professor at the Universityof Coloradotestifies, “The evidence for the biological basis for homosexuality is very, very strong. It’s coming from a lot of different areas. The religious right has been very, very successful at creating controversy where there is none. The scientists who study in this area, it’s not a question that there’s a biological component, it’s just how that biological component is working.” Or as Dr. Alan Sanders, a psychiatric geneticist at Evanston Northwestern Healthcare Research Institute puts it, “”I think the evidence is pretty convincing already that a substantial contribution to sexual orientation comes from genetics. It’s probably the single biggest factor that we know about.”
An In Depth Look
Clearly genetics is linked to homosexuality. But in order for someone to make the claim that someone is “born that way,” biological factors have to be the ONLY cause. Note that Dr. Sanders said that genetics are a “substantial” contributor, but not the sole contributor. As Dr. Brian Mustanski, a psychology professor at the University of Illinois believes, “Since sexual orientation is such a complex trait, we’re never going to find any one gene that determines whether someone is gay or not. It’s going to be a combination of various genes acting together as well as possibly interacting with environmental influences.” Dr. Mustanksi opens the door for the possibility for outside environmental influences.
Let us go back to the twin studies. Geneticist Sven Bocklandt of the David Geffen School of Medicine of UCLA (and protégé of Hamer) is also conducting genetic research on twins based on Hamer’s study. The DNA in identical twins are the same, but their genes are not always, which is why he believes you can have in some cases both twins come out gay, or just one of the twins come out gay. This is due to methylation. You may inherit genes from your mother and genes from your father, but methylation determines which of those genes is active and which are not, and methylation is influenced by diet and environment. So even if one truly believes homosexuality is rooted in genetics environment still comes into play.
But the twin studies conducted by Hamer has been and still is challenged and overturned. Dr. George Rice, a neuroscientist at the Universityof Western Ontarioreplicated Hamer’s study on twins and completely overturned it. Dr. Francis S. Collins, Director for the National Institute for Health, remarked that Hamer’s study “grabbed headlines” but was “widely overstated.” Dr. William M. Byne, Director of the Laboratory of Neuroanatomy and Morphometrics at Mount Sinai School of Medicine wrote of Hamer’s study, “Thirty-three of 40 pairs of gay brothers the researchers studied inherited the same version of this chromosome region—significantly more than the 20 pairs (half) expected by chance … [but the researchers] warned against making too much of their results, however ‘We have never thought that finding a genetic link makes sexual orientation a simple genetic trait like eye colour. It’s much more complex than that.’ … seven of the original 40 pairs of brothers did not share the same version of this critical region, for example. And other studies have shown that even the identical twin of a gay man has only a 50 per cent chance of being gay himself. So Hamer’s gene, whatever it turns out to be, is neither necessary nor sufficient to determine homosexual orientation.”
Hamer was not the only one to conduct twin studies though, many have and continue to test twins for genetic correlations. A recent study in 2008 revealed that 27% of homosexuality in genetically contributed. But the error range for the study was 95% meaning that genetic contribution could be much lower. The study also reveled that non-shared environmental contributions greatly predominate, and are in that case the largest causes of same-sex attraction (SSA). Biochemist Dr. Neil Whitehead writes of the report, “Are genetic contribution results of say 27% important? No. In the twin studies world the influence would be classified as weak to modest. And any influence is indirect – it is likely to be something like an innate tendency to be very sensitive to the opinions of others. However, even this weak or modest genetic contribution is probably greatly overstated.” And furthermore, “Twin studies are favorites of mine because of the potential light they throw on the origins of same-sex attractions (SSA). The latest one (Santtila et al., 2008) is three times larger than any previous study – in fact, larger than all the rest put together. Does this latest study teach us something new? Quick answer: No. It confirms the best recent studies, which tell us that genetic factors are minor; non-genetic factors are major.”
Another study conducted earlier in 2002 by Yale and Columbiaresearchers Bearman and Bruekner published in the American Journal of Sociology found that the genetic contribution was zero and that chance was a very important factor. If one male twin had SSA, there was a 7% chance the co-twin had SSA, for females the results drop to 5%. Why are these results so different from others? The researchers stated that other studies were conducted from volunteers, and therefore there was a bias. Bearman and Bruekner’s study consisted of a more random sample, and thus results were much lower.
Collins writes of twin studies as follows, “An area of particularly strong public interest is the genetic basis of homosexuality. Evidence from twin studies does in fact support the conclusion that heritable factors play a role in male homosexuality. However, the likelihood that the identical twin of a homosexual male will also be gay is about 20% (compared with 2-4 percent of males in the general population), indicating that sexual orientation is genetically influenced but not hardwired by DNA, and that whatever genes are involved represent predispositions, not predeterminations.”
As for LeVay’s study of the anterior hypothalamus INAH-3, a smaller INAH-3 in the brain is like the evidence of brain activity patterns mentioned earlier; it is only evidence of effect not cause. All we can conclude from LeVay’s study is that homosexuality and smaller INAH-3s are associated. There is no proof that a smaller INAH-3 causes homosexuality. Besides one could simply argue the opposite; that homosexuality causes the INAH-3 to shrink. When Byne completed the study of the INAH-3 he found that though they were indeed smaller in gay men, they contained the same number of nerve cells as straight men. Since nerve cells of the INAH-3 only develop in the earliest stages of brain development in the womb, the size of the INAH-3 must be determined sometime later.
It should also be understood that measuring this brain structure is very difficult considering it is smaller than a snowflake, and we still are determining the exact function of INAH-3. Some researchers use volume to measure INAH-3, some use neurons. Biologist, Psychologist and Licensed Clinical Counselor Dr. Jerry Bergman writes the following on this study, “If LeVay’s research is valid, it indicates that homosexuality is caused by a biological pathology, since he found that the INAH 2 and 3 (the preoptic nuclei) was much smaller in homosexual compared to normal heterosexual males, indicating it is caused by disease, hormone imbalance or some other abnormality. If it is caused by pathological conditions, it is not normal.”
As far as Reiner’s study of deformed children, he was working only with children establishing gender identity, not sexual orientation/SSA. One could use his study to support that gender identity has underlying genetic causes, but not SSA. It is surprising how often his work is brought up in the realm of this debate despite being a completely different topic. The reasoning is thought to be because the layman tends to get gender identity and sexual orientation confused, unable to distinguish the difference between the two. It is in understanding sexual orientation, and specifically SSA, that we can learn that its cause, although linked to genetics, has a multitude of causative factors.
SSA Causative Factors
According to Lewis, there are stages at which we develop certain identities. Our genetic sexual identity (XX or XY) is established at fertilization. Our phenotype sexual identity (reproductive organs) is distinguished after 8 weeks of fertility and continues to develop through puberty. Gender Identity (feelings of being male or female [Reiner’s study]) is established during childhood. And lastly, sexual orientation (attraction to the same or opposite sex) is determined during childhood. Why does it take so long for sexual orientation to become established if it is claimed to be “predetermined” genetically? Sexual orientation cannot be established any earlier because we’re dealing with children. Infants do not have a sexual preference from the womb that can be measured or known. Sexual orientation is a development that occurs overtime, and because it develops overtime it is therefore influenced by environment.
Licensed family therapist and Assistant Professor of Psychology atPalm BeachAtlanticUniversity, Dr. Julie Harren writes that sexual orientation (and more specifically homosexual orientation) is establish from a multitude of factors that all come together in the form of an equation:
Genes + Brain Wiring + Prenatal Hormonal Environment = Temperament
Parents + Peers + Experiences = Environment
Temperament + Environment = Homosexual Orientation
As you can see above, there are many factors that come into play through the process of homosexual development. Bergman writes on the following subject, “An enormous amount of research has been completed on the influence on homosexuality of such factors as passive fathers, domineering mothers, marital relationship abnormalities, closeness and similarity of siblings, relationships with peers, adolescent sexual experiences, feminine interests in males and masculine interests in females while growing up, and numerous other factors. So far, a consistent pattern has not been determined. Likely numerous factors exist which influence homosexual development, any one of which is often not critical. Suffice to say that all of the factors that have been proposed and have been to some degree documented as influential are regarded in Western society as pathological, that is, a domineering, overbearing mother and a weak, passive, ineffective father.
Regardless of the validity of these studies, they all point to pathology in interpersonal relationships as an important or influencing factor in the development of homosexual behavioural tendencies. No one has noted that loving siblings and parental relationships in which the power is equitably shared causes homosexuality, although some have noted that this environment will not necessarily preclude a child from developing homosexual tendencies. …a variety of experiences, many of which have little to do with the person himself or herself, can cause one to become a homosexual, depending on the degree that one’s early diffuse sex drive is conditioned toward persons of the same sex and away from persons of the opposite sex.”
I think it is safe to conclude that there is no one sole cause for homosexuality. Trying to say so is to ignore the observable complexity of the issue. What is observable is a highly complex matrix of potential influences that individually are not significant, but in combination can produce a wide variety of orientations, which is probably why the outcome is not as simple as gay or straight, but instead gay, straight, bisexual, transgendered, etc. What we should ask ourselves is why does homosexuality need to be biological? Why are advocates of homosexuality trying to push a genetic cause?
Why Fight For A Genetic Cause?
Our culture is one that is overall not very accepting of the homosexual culture. Granted, compared to other countries and civilizations one could argue thatAmericais incredibly tolerant and accepting of homosexuals. Regardless there is this predominant mindset and agenda being spread that homosexuality is predetermined. That gays and lesbians are born that way. The reasoning behind which is obvious; if people are born gay, how can you justify any form of mistreatment, prejudice, or dislike of them? After all, they can’t control what they are. The agenda is to force acceptance, hence why so many are striving to promote “evidence,” genetic or otherwise, that gay people are born gay.
Biologist Ruth Hubbard writes, “… many people seem to believe that homosexuality would be more accepted if it were shown to be inborn. Randy Shilts, a gay journalist, has said that a biological explanation ‘would reduce being gay to something like being left-handed, which is in fact all that it is…’ Questions about the origins of homosexuality would be of little interest if it were not a stigmatized behavior. We do not ask comparable questions about ‘normal’ sexual preferences. … Still, many gay people welcome biological explanations and, in recent years, much of the search for biological components in homosexuality has been carried out by gay researchers.”
Dr. A. Dean Byrd, a psychologist and former president of the National Association for the Research and Therapy of Homosexuality, writes, “Unfortunately, much of the research in areas such as homosexuality, has been not only misrepresented in the media but by the scientists themselves through the tendency to overestimate the quantitative contribution of their findings.” Or as Michael Bailey, a psychology professor for Northwestern University and researcher for the “gay gene” writes, “People are going to make a big deal out of this because people are obsessed with this topic. We obviously find this topic very interesting, but people often make more than they should of these kinds of results.”
Another thing to be considered is the actual genetic causes in question. Many of the genetic links associated with homosexuality, that advocates are so quick to propagate for the “born gay” agenda, are in fact abnormalities. Dr. John Shea, medical advisor for the Campaign Life Coalition writes, “If correct the theories would thus show the opposite of the normalcy of homosexuality, which the mainstream media are attempting to posit with the coverage… ‘I was born abnormal, and therefore I’m normal’ is not good logic.”
On this topic, Bergman writes, “Even if a biological factor exists for some persons, it is another question altogether as to whether homosexual behaviour is desirable or even acceptable. Change is admittedly difficult, but the level of success in treating other sexual disorders such as pedophilia is also extremely low. The latter individuals also claim that they have strong attractions for young children, and have minimal or no attraction to adults of the opposite sex. Some indications also exist that pedophilia may be biologically influenced. This alone would not argue that laws against pedophilia behaviour should be rescinded, or that this behaviour is a normal, acceptable sexual preference. If it were shown that many behaviours now classified as abnormal, including sadomasochism, various fetishes, coprophilia, necrophilia, etc., are likewise influenced by biological factors, this may help us to understand persons who indulge in these practices, but it would likely carry little weight in convincing society to embrace these behavioural forms as normal or desirable.”
So even if we could conclude with certainty that homosexuals are in fact “born that way,” it still should not change how we approach homosexuality. But since it is evidently not genetically predetermined we should no longer latch on to the theory that being born gay will in anyway help homosexuality inAmerica. Believing that to prove being born gay will settle all problems related to homosexuality in poor logic and bad science.
Research scientist for thePalo AltoResearchCenter, Nick Yee writes, “In this crossfire of whether homosexuality is genetic, I contend that our finding of a gay gene will not really get us anywhere in the debate. This is because we know that bad things can be genetic. For example, the mental retardation that accompanies Down Syndrome is caused by a genetic defect. So is cystic fibrosis that causes problems in human respiration. Accompanied by other abnormalities such as color-blindness or Klein-Felters, the list of genetically caused defects is not short. Even if a gay gene were found, this would not grant homosexuality moral or social acceptability because it could still be regarded as a defect or an abnormality.
Some homosexuals also feel that finding a gay gene might diminish prevalent homophobia. This is also a naïve view. Racism has not diminished because we know that blackness or whiteness is genetic. Sexism exists even though we know that sex is genetic. Since finding a gay gene will neither make homosexuality morally or socially acceptable nor will it diminish homophobia, it is clearly the wrong place to be looking. The gay gene debate and arguments over whether it is genetic or not are superfluous and can have no real impact on the important aspects of the discussion of whether homosexuality should be acceptable.”
Evolution and Homosexuality
Now we come to another problem on this topic that further undoes the born gay theory; evolution. If homosexuality has its roots only in genetic and biological causes than it overturns evolution simply because it still persists! Evolution would require only the most beneficial traits for survival and reproduction to be passed on through natural selection. If homosexuals don’t produce offspring, for obvious reasons, than how could their genes be passed on for millions of years?
Bailey writes, “Frankly, the biggest problem of the genetic possibilities is the evolutionary problem. And I don’t think that Dean [Hamer] has taken that problem seriously enough.” Lee Ellis, a sociologist for Minot State University, writes of homosexuality being rare, “Evolution isn’t very good at explaining oddities.” Bergman writes, “Since nature would consistently select those organisms with stronger heterosexual drives, it would become stronger and stronger until it would eventually become the all-encompassing human drive, more important than food and other life preservation needs. Evolution would not select for length of life beyond childbearing years, but primarily for the number of offspring that an individual was able to produce… Homosexuality would obviously usually not produce higher levels of reproduction than heterosexuality—evolutionary selection would consistently work in the opposite direction, selecting for heterosexuality—and any biological factors positively influencing homosexual feelings would rapidly be selected out. Homosexuality is thus not easy to explain from this world view.”
Though many scientists have tried to rationalize homosexuality and evolution their theories are always incredibly vague, full of loop holes, and/or dependant on very creative speculations of human homosexuality millions of years ago, and therefore easily refuted. This has in fact lead many evolutionists to conclude that homosexuality is in fact influenced by environmental, sociological, and physiological causes as well. After all, genetically alone, it cannot be explained via evolution. It pushes one into a corner. If you believe homosexuality is purely genetic you must deny evolution. If you believe in evolution, you must deny homosexuality is purely genetic.
This does open the door to the possibility that a creationist could believe that homosexuality is purely genetic. Couldn’t God have created people gay? And if a gay gene was to be found hypothetically, doesn’t that mean God is creating people gay? This would of course overlook two topics in the scripture of the Bible. One being that homosexuality is not approved of by God, and two, we live in a fallen world cursed with sin. After all, children are born everyday with all kinds of genetic disorders which we never attribute to God, but instead the effects of a sin cursed world. So even if we were to find a gay gene that still doesn’t mean God intended or wanted them to be that way. To do so would suggest that God intentionally wanted a child to be born with autism or a chromosome disorder. As Bergman writes, “The Creator-designed sexual orientation is heterosexual, and any deviation from this must be due to an aberration in either biological or psychological development.”
Homosexuals Against the “Born Gay” Theory
There tends to be a generalization made in reading articles like these in that the author and all noted doctors and scientists quoted are anti-homosexual, and are therefore hell bent on destroying homosexual progress. But the “born gay” theory is opposed by homosexuals as well, which should not be overlooked on this topic.
Karla Mantilla, an author for the lesbian-feminist journal Off Our Backs: A Woman’s News Journal, wrote, “Of course it’s a choice—how could it not be?” Gay writer Joe Sartelle writes, “”I think that the popularity of biological accounts of homosexual desire among gay people has to be understood as a way of coping with deeply-rooted homophobia. What else can it be when we defend ourselves by saying things like, “Do you think anybody would choose to be this way?” This is a defensive position, one that implicitly accepts that there is something wrong with homosexuality, that it is indeed an abnormality which demands to be explained.” A multitude of resources for the viewpoint that homosexuality is a choice and not genetically predetermined can be found at http://www.queerbychoice.com.
Why Does It Matter?
The “Born Gay” Theory needs to be addressed for multiple reasons: 1) To believe in such is simply put, bad science. 2) Believing in such will not help the homosexuals inAmerica(in fact, many argue that finding a primary genetic cause will lead to genetic testing of embryos that would influence abortion and could lead to the eventual extermination of homosexuals). 3) This belief destroys the possibility of therapy for homosexuality because it falsely asserts that you cannot change who you are.
As Harren writes, “The inaccurate concept that homosexuality is solely biological is extremely misleading. Many therapists tell their clients that homosexuality is biological and therefore unchangeable. These therapists encourage their clients to embrace a gay identity, even when such clients are seeking change for their orientation. In doing so, therapists negate clients’ rights to self-determination. Clients have the right to choose their own goals for therapy and should be allowed to pursue the path they desire. Clients should not be discouraged from pursuing change when change is what they seek. In order for clients to have the options made available to them, it is vital that therapists as well as clients become better educated on this issue.”
The therapy for homosexuals itself is heavily criticized by activists because it asserts that homosexuality is a problem that needs to be corrected. Advocates for therapy on the other hand assert that is a choice that can be corrected. And that giving homosexuals the opportunity to change their orientation should not be frowned upon. But it is hard to formulate your own unbiased opinion on the matter when the media has been overwhelmingly biased on the issue. As Byrd writes, “Whenever any form of reorientation therapy is discussed in the mainstream media, it usually involves someone who either never went through such therapy, or went through a faith-based process and became disillusioned. This is poor journalism and doesn’t serve the public. Consumers of print media and broadcast media deserve better information. We are asking for a fair hearing of our work – not distortions or characterizations.”
It is in fact the reparative therapy of homosexuals itself that further dismantles the “born gay” theory. After all, if homosexuality is a purely genetic or biologically caused behavior, how can it be treated? The National Association for the Research and Therapy of Homosexuals has a long list of successful cases of rehabilitation. There is the successful PFOX (Parents and Friends of ExGays and Gays) non-profit organization. There is also faith-based rehabilitation programs like HA (Homosexuals Anonymous). To account all the men and women that by self testimony declared themselves to have been treated for homosexuality clearly demonstrates that homosexuality is not purely genetic.
The Final Say
To conclude, let us ask the question again: Is there genetic or biological proof that people are born gay?
LeVay writes, “Although efforts have been made to establish the biological basis of sexual orientation, for example, by the application of cytogenetic, endocrinological, or neuroanatomical methods, these efforts have largely failed to establish any consistent differences between homosexual and heterosexual individuals.”
Byne writes, “What evidence exists thus far of innate biological traits underlying homosexuality is flawed.”
Bergman writes, “The extant empirical research supports the creationists’ hypothesis, concluding that homosexuality is due either to environmental, social or physiological pathology. The research which indicates biological factors are involved in homosexuality does not conclude that biology is destiny, only that certain abnormal factors, both genetic and environmental, influence the development of the eventual sexual response. That these are abnormal supports the conclusion that the Creator designed a sexual response which fulfills the goal to reproduce, multiply and bond, and that other sexual responses are not designed, but are the result of pathological factors.”
Harren writes, “Although not supported by the research, many therapists believe that homosexuality is solely biological in nature, and therefore unchangeable. Yet despite ongoing efforts, researchers have not discovered a biological basis for same-sex attractions. In fact, many researchers hypothesize that a homosexual orientation stems from a combination of biological and environmental factors.”
Whitehead writes, “Genes are responsible for an indirect influence, but on average, they do not force people into homosexuality. This conclusion has been well known in the scientific community for a few decades but has not reached the general public. Indeed, the public increasingly believes the opposite.”
And even Bocklandt points out that after 14 years of research there has been no evidence that genes are the sole cause of homosexuality and no one has yet to pinpoint the base pairs that could cause it.
In conclusion I think it is most appropriate to assert that there are a wide variety of causes for homosexuality, and though our genetics play a role in the equation, the role is a very small role. Is this good or bad to gay the community? I’d say neither, it is neutral. For Christians it doesn’t matter whether homosexuality is genetic or not because it doesn’t change Christian theology. But one thing is for sure: There is no one that will benefit from maintaining the unscientific notion that people are “born gay.”
 Lewis, R., (2008) “Human Genetics: Concepts and Applications,”McGraw-Hill,New York:NY, pp. 113
 Lewis, R., (2008) “Human Genetics: Concepts and Applications,”McGraw-Hill,New York:NY, pp. 114
 Lewis, R., (2008) “Human Genetics: Concepts and Applications,”McGraw-Hill,New York:NY, pp. 114
 Lewis, R., (2008) “Human Genetics: Concepts and Applications,”McGraw-Hill,New York:NY, pp. 114
 Byne, W., (1994) “The Biological Evidence Challenged,” Scientific American 270(5):26-31, pp. 26.
 Santtila, P., Sandnabba, N.K., Harlaar, N., Varjonen, M., Alanko, K., & von der Pahlen, B. (2008). “Potential for homosexual response is prevalent and genetic,” Biological Psychology, 77(1), pp. 102-105
 Bearman, P.S., & Bruckner, H., (2002) “Opposite-sex twins and adolescent same-sex attraction,” American Journal of Sociology 107, pp. 1179-1205.
 LeVay, S., (1991) “A difference in hypothalamic structure between heterosexual and homosexual men.” Science 253:1034–1037, pp. 1034.
 Lewis, R., (2008) “Human Genetics: Concepts and Applications,”McGraw-Hill,New York:NY, pp. 114
 Hubbard, R. & Wald, E., (1993) Exploding the Gene Myth: How genetic information is produced and manipulated by scientists, physicians, employers, insurance companies, educators, and law enforcers, Beacon Press, Boston; MA, pp. 94-95.
 LeVay, S., (1991) “A difference in hypothalamic structure between heterosexual and homosexual men,” Science 253:1034–1037, pp. 1034.
 Byne, W., (1994) “The biological evidence challenged,” Scientific American 270(5):26-31, pp. 26.