Homosexuality, Post 4: The Science

Biological and Psychological Factors

Defining the Different Dimensions of the Debate on the ‘Causes’ of Homosexuality:

The debate is a complex one.  On the one hand there is the ‘nature/nurture’ debate as to the causes of homosexuality.  Then on the other hand there is the essentialist/constructionist debate.  People from a range of perspectives are found on all sides of the debate.

The ‘nature / nurture’ debate is simply the question as to whether homosexuality is something that people are born with, or whether it is something they learn from their environment.  Most people think that both nature and nurture play a significant role, but argue over the relative balance of these two forces in individual development.  Then there is further debate about whether homosexuality (whether it arises mainly from nature or by nurture) can be altered, either by biological or by psychological means.

A further debate is between the essentialist and the constructivists.  Essentialists believe that homosexuality is a fixed (either by nature or by nurture) aspect of a person, in much the same way as left-handedness.   Social constructionists, however, point to the variety of ways in which homosexuality is understood (or not) in different cultures and times and say that our concept of ‘homosexual’ is simply our culture’s way of describing what’s going on now, and doesn’t actually refer to anything more than a cultural concept.  And again, there is further debate within these positions as to whether it is possible or good to change what may either be essential to the human person, or a socio-cultural construct.


The gender of their sexual partner, not any specific activity, is what makes a person homosexual.  I have chosen not to focus upon specific homosexual activities in this section, but rather to focus on homosexual attraction and its origin.  This is partly because the literature is most significantly weighted in this direction, but, more significantly, while there is some information regarding homosexual activity from a medical point of view, it is not essential to the debate.  There is a great deal of data linking homosexual men, especially, with high-risk sexual behaviours, promiscuity, and higher levels of psychological distress[1].  This data has been used to argue that homosexuality is, in itself, pathological.  Some writers point out that the increased levels of distress, the high-risk activities, and the impermanence of homosexual relationships (sometimes to the point of anonymity) can be explained as a response to negative social stereotyping and discrimination.  This explanation is not particularly convincing, as it suggests that the majority of homosexual men are unable to make their own decisions about how, where, and with whom they engage in sexual activity.  Nevertheless there is certainly an element of truth in it for some individuals.  The more compelling reason to by-pass this aspect is simply that it is not an issue for us.  The church has no doubt that risky sexual behaviours and promiscuity or anonymous sex is against the will of God.  We are being asked, instead, to consider the morality of a relationship that conforms to the Christian norm of marriage (exclusive, committed, caring) in every respect but the key one of gender.  And though the most common forms of same-sex sexual behaviour are seen medically as potentially harmful, the behaviour does not define the relationship.  Homosexual couples engage in a wide range of sexual activities (as do heterosexual couples); it is not the activity that makes them homosexual, it is the gender of their partner.

Two Basic Questions:  So what else does medical science and research have to tell us?  Scientists have been asked two questions about homosexuality; “What causes it?” and “Can it change?”  We may or may not agree that these are good questions, but they comprehend nearly all the scientific literature I have seen on this issue.

There is certainly not any agreement in any group about any of the scientific findings related to homosexuality.  These studies tend to focus upon early childhood experiences and family relationships, genetics, brain structures, and hormonal activity – especially before birth.

Do Parents Make their Kids Gay? Family Relationships first came to the sustained attention of science through the fledgling discipline of psychoanalysis in the 1800s.  It was they who coined the word ‘homosexuality’ to describe an enduring pattern of homoerotic attraction.  This concept wasn’t translated into English until the early 1900s.  Because psychoanalysis focuses upon the development of psychological problems in the individual by reference to their closest (usually family) relationships, they quickly developed a theory of homosexuality as a condition birthed out of an over-bearing mother and an emotionally distant father.  Homosexuality was described as a regression to an earlier developmental stage or a state of arrested psychosexual development.   Variants on this theory[2] are still popular today among those therapists who still provide a service to those who seek to change their sexual orientation[3].

Research into the reliability and validity of this understanding of homosexuality is heavily dependant upon the case notes of the therapists who have used these theories, and as therapists tend to find what they expect to see, these case histories have usually not carried a great deal of weight in scientific debate.

What Difference does it make Having Lesbian Parents?

I did find one careful scientific study  which examined the impact of family on the likelihood of homosexual development, but it was attempting to measure the impact of being raised by lesbian parents, rather than the more traditional category of ‘over-involved mother’.  The result was that:

Although no significant difference was found between the proportions of young adults from lesbian and heterosexual families who reported feelings of attraction toward someone of the same gender, those who had grown up in a lesbian family were more likely to consider the possibility of having lesbian or gay relationships, and to actually do so.  However…the majority of children who grew up in lesbian families identified as heterosexual in adulthood, and there was no statistically significant difference between young adults from lesbian and heterosexual family backgrounds with respect to sexual orientation  . 

The authors note that their study did not distinguish between nature or nurture at all, but they do provide some useful evidence for distinguishing between homosexual attraction, activity, and identity.

(Golombok and Tasker 1996, 8)



Does Sexual Abuse ‘Cause’ Homosexuality?

A more recent finding related, not so much to family, but certainly to early child-hood experience, is that reported from the University of Otago study of 13 000 ordinary kiwis.  They found that “of those who reported sexual abuse or rape in childhood, about 15 per cent were non-heterosexual. Of those who had not had these experiences only five per cent were non-heterosexual.” (Todd 2010)  Therefore, being sexually assaulted in childhood means someone is three times more likely to identify as “non-heterosexual” in later life.  Again, being abused does not ‘make’ someone homosexual, nor have all homosexual people suffered abuse!  But there is clearly a link of some sort between early childhood experience and homosexuality in some cases.

The More Older Brothers You Have the More Likely You are to be Gay!  Interestingly, one of the more reliable scientific findings is about family relationships – but of an unexpected form: there is, apparently, a significantly higher possibility of a man being homosexual the more older brothers he has[4].  The most recent findings have controlled for environmental factors (nurture) by checking for correlations with non-biological (eg adopted) brothers, and also with biological brothers raised outside the family.  The mechanism here is thought to be the development, over time, of an immune reaction in the mother to the male hormones of boy foetuses, leading to a suppression of male hormones in those boys in the womb.  There is, however, no direct evidence for this mechanism apart from some animal studies, and it remains speculative.  What has been demonstrated is that this single biological factor (number of older brothers) has a consistent impact, for whatever reason, independently of environment.  Again, though no-one knows why this is, it does seem to indicate that homosexual preference has some biologically causative factors.

Other studies[5] examine a range of biological factors that appear to be related to homosexuality.  There have been several studies that seem to show distinct differences in the structures of various areas of the brain, but none of these have been conclusive, nor have they been replicated.  While the researchers have found that there may be some evidence of biological causes for sexual preferences, they cannot demonstrate conclusively that the differences they’ve noted are not caused by the sexual preference rather than causing it, nor can they tell us how powerful these factors are, if they are causative, and nor can they describe in detail the link between the structure of the brain as they’ve observed it, and the function of the brain as it relates to sexual preference.  These studies also tend to rely heavily upon analogous studies with a variety of animals; this is valuable as it is possible to carry out experiments with animals that it would be extremely unethical to attempt with humans, but it is also limited and we should note that while homosexual behaviour has been observed in many different animals, in the wild and in captivity, and has been induced in several species through a variety of methods, there is still a big difference between the largely instinctive behaviours of rats and dogs, and the strongly socialised behaviours of human beings.

Along similar lines, unusual prenatal hormonal fluctuations sometimes associated with maternal stress, and the use of some drugs, can be shown to lead to something like homosexual preference in some mammals – and maybe in humans.

My Genes Can’t Make Me Gay:  Genetic factors have also been focused upon, and I recall the announcement in the newspapers that the ‘gay gene’ had been discovered, some years ago.  Those reports were, however, somewhat exaggerated.  Although a twin study from 1991[6] seemed to point to a definite genetic component to homosexuality, it was accused of sample bias and a later study with an unbiased sample led to a retraction of the earlier findings[7].  Other gene studies[8] have found evidence that there is a genetic element to homosexuality for at least some; but it is not determinative.  What does this mean?  Essentially, very few scientists would agree with the statement, “My genes made me do it.”  To illustrate this debate, let’s consider the Bocklandt et al study.  They found that

Human sexual preference is a …trait with a substantial genetic component.  Linkage of male sexual orientation to markers on the X chromosome has been reported in some families.  Here, we measured X chromosome inactivation ratios in 97 mothers of homosexual men and 103 age-matched control women without gay sons.  The number of women with extreme skewing of X-inactivation was significantly higher in mothers of gay men (13/97 = 13%) compared to controls (4/103 = 4%) and increased in mothers with two or more gay sons (10 / 44 = 23%).  Our findings support a role for the X chromosome in regulating sexual orientation in a subgroup of gay men.

In other words, a specific genetic variable was found more frequently in the mothers of homosexual men than in the mothers of heterosexual men.   But note that not every mother of a homosexual man had these genetic markers – it’s not necessary for this genetic variable to be present in the mother for the son to be homosexual –  also several mothers of heterosexual sons did have these genetic markers – so having these markers does not necessarily make your sons homosexual.  These researchers have simply found that there is a relationship between specific genetic factors and homosexuality, but they do not have an explanation for how these genes affect the development of homosexuality.  Clearly there is some genetic force at work, but how it works and how strong it is is up for debate.  Genes cannot make us gay[9].  They may make us more likely to be so, but there are clearly many other factors at work[10].

What all these studies demonstrate is the possibility of homosexual attraction, at least in some people, being strongly affected by biological factors as well as by events in early childhood, but none of them come close to answering the question of “what causes homosexuality?”

[1] (Fergusson, Horwood and Beautrais 1999)

[2] (A. Comiskey 1989, 1990) (Dallas 1994) (Nicolosi 1996) (Payne 1985, 1996)

[3] In doing so they differ from the American Psychological Association and the American Psychiatric Association who state that homosexuality is normal, not pathological, and shouldn’t be changed.

[4] (Bogaert 2006)

[5] (Burr 1994), (Ellis and Ames 1987) (LeVay 2004) (LeVay and Hamer, 1994) (Perkins and Roselli 2007) (Savic, et al. 2001) (Swaab DF 1995)

[6] (Bailey and Pillard, A Genetic Study of Male Sexual Orientation 1991)

[7] (Bailey, Dunne and Martin, Genetic and Environmental Influences on Sexual Orientation and Its Correlates in an Australian Twin Sample 2000)

[8] (Bocklandt, et al. 2006)

[9] Biology or Genetics never dictates human behaviour; at the very most it may influence it to some degree, but that degree is much less that the environmental influence.  (Whitehead 1996, 20)

[10] Laurie Guy commends L. Ellis and L Ebert’s book, Sexual Orientation: Toward Biological Understanding, (Westport, Conn, 1997) described as “the best argument for a biological understanding” of homosexuality.  He says “One should note that all of its chapters argue that biology is a partial explanation, but none …argue that biology is a total explanation.” (Personal correspondence, August, 2012)


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