Sexual Orientation

Dr. C. George Boeree


The roots of homosexuality are still a mystery - although only a little more a mystery than the origins of heterosexuality!  Like almost everything, it is likely to involve both genetic-physiological roots and cultural-learning roots.  Here are some of the possible factors:

First, there may be genetic foundations for homosexuality.  J. Michael Bailey and Richard C. Pillard, for example, discovered that 52% of the identical twins of male homosexuals were also homosexual, compared to only 22% of non-identical twins.  Likewise, they found that if one identical twin is lesbian, in almost 50% of the cases studied, the other twin is lesbian as well, in comparison to 16% of the non-identical twins.

People always ask:  If homosexuality is genetic, how does it get passed on to future generations?  Homosexuals do have children, of course, but at a considerably lower rate than do heterosexuals.  So why hasn't it "evolved out" of us?  There are a number of possibilities, but the most obvious one is that the genes responsible for sexual orientation are similar to those simpler genes that account for sickle-cell anemia:  If you have a sickle-cell gene from mom and a sickle-cell gene from dad, then you will get sickle-cell anemia, a deadly disease.  But the sickle-cell gene remains a part of the population because, if you only have one of them you will be more resistant to malaria!

In the same way, if you inherit a "full dose" of genes for homosexuality, you may be less likely to reproduce.  But a "half dose" may actually make you more likely to survive and reproduce.  Women with some characteristics more associated with men (men's assertiveness, perhaps?) may do better than their more feminine sisters.  Likewise, men with some characteristics of women (perhaps more affection for their children?) may do better than their macho brothers.

Even with a genetic component to homosexuality, we need to understand that genes are only responsible for the making of proteins, and we still need to explain how a protein can influence our sexual behaviors.  One fruitful path is, naturally, the "sex hormones," especially testosterone and estrogen.

Estrogen, the female hormone, is the default hormone:  If testosterone is not present in a developing fetus, it will develop into a girl, whether it actually has the genetics of a female or not.  On the other hand, if testosterone is somehow added to the developing fetus, it will develop testes, a penis, and so on, even if it has the DNA of a female!  There are certain circumstances where these events occur.

Both men and women have testosterone - it is crucial to growth - but men have something on the order of 100 times the amount.  In rats and mice, low levels tend to be associated with lordosis, which is the technical term for the sexual posture that female animals tend to take.  High levels in animals is associated with a tendency to mount other animals.

Men with higher levels of testosterone tend to have a more masculine appearance, tend to behave in a more masculine fashion, and tend to be more aggressive.  Men with less testosterone tend to look and act somewhat more like women, and women with more testosterone than other women tend to look and act somewhat more like men.  However, there is no overpowering connection between testosterone levels and homosexuality in human beings:  Researchers have found no differences between male homosexuals and heterosexuals when it comes to how much testosterone is circulating in their blood.  Apparently, our sexual orientation is a bit more complicated than that of rats and mice!

Some other studies suggest that there are differences in the way that men and women respond to estrogen:  Women respond by producing more of a pituitary hormone called luteinizing hormone or LH.  Men do not.  But homosexual men responded more like women, which suggests that homosexual men have a more "female" hypothalamus.  We would then expect that lesbians would have a more "male" response, but that is not the case.  In fact, they respond with even more production of LH than heterosexual women do - as if they were more "feminine" rather than less!  This suggests that homosexuality works differently in men and women.

There have been studies of brain structures, looking for differences between men and women and between heterosexuals and homosexuals.  Some small differences have been tentatively identified, but the research is still only in its early stages.  And we have no way yet of knowing if these differences cause the hormonal differences, or are caused by them!

Still, the argument that at least a good portion of our sexual orientation is biological is hard to deny.  Homosexuals often say that they have felt an attraction to the same sex as long as they can remember.  And studies by Martha McClintock and Gilbert Herdt show that both homosexuals and heterosexuals develop attractions to the same or opposite sex at around the age of ten, two or three years before they begin developing the clearer signs of puberty.  With heterosexuality our clear cultural norm, we should not see any same-sex attraction if it were only a learned behavior!  Instead, we see somewhere between 3 and 10% of the population considering themselves homosexual.  (The figures are so ambivalent, no doubt because of that cultural norm!)

The relationship between an instinct and upbringing is a matter of imprinting:  The precise nature of a complex stimulus is usually not directly supplied in the genetic programming of the brain.  It is more efficient to program the brain to attach an instinctual response to a stimulus while experiencing that stimulus. So goslings follow the first large moving object they see, to use the classic example.  There is also a critical period involved during which this imprinting occurs.  For geese, this is a matter of a couple of days.

Freud’s theorizing about sexual orientation is basically the same as this.  During a critical period - which he felt was between the ages of three and six - sexual orientation is fixed by a complex process of family relations he called the Oedipal crisis.  A young boy begins by being attached to his mother.  As he gets older, he acknowledges his father’s priority in relation to mom, and substitutes girls and later women for mom as his primary sexual interest, and begins to identify with his father, from whom he learns what it means to be male.  A similar process, with complications, occurs in young girls.  Freud’s explanation is muddied by his use of the bizarre concepts of castration anxiety (the supposed fear boys have of losing their penis) and penis envy (the supposed desire girls have for growing one).

Like most psychologists, I don’t agree with too much of Freud’s theory.  But there is some sense in it:  I suggest that, by the age of 3 or 4, social learning has already informed the child of their gender, and has (for most) strongly reinforced identifying with the same sex parent.  The relation between mom and dad becomes the model for the child, and later sexual fantasy centers around the gender of the opposite sex parent.  This may be reinforced by the opposite sex parent playing the part of "role reactor," that is, by engaging in non-sexual flirtation with the child ("daddy’s girl" and "momma’s little man," and the like).

Freud once said that infants are "polymorphously perverse," by which he meant that they enjoy sensual pleasure in any form, from any source.  I agree with him on this.  It takes the imprinting process to focus our sensual, and later sexual, enjoyments on one gender or the other.  If that imprinting process is disturbed in some fashion from the culturally traditional one we just talked about, we may find the child tending towards sexual orientations other than the purely heterosexual.  This could happen in many ways:

(Note that, while I use words like parents and mom and dad, the same roles in the family dynamic may be taken up by other relatives and close non-relatives.)

If we take both the genetic-hormonal explanation and the family-learning explanation into account, we may have the beginnings of an understanding of homosexuality (and heterosexuality):  A boy or girl who leans towards homosexuality biologically, and who has a family situation that encourages that leaning, is more likely to grow up gay or lesbian or bisexual.  One who has neither the biological tendency nor the family situation is more likely to grow up straight.

There is one thing I can say about homosexuality with great confidence: Being homosexual in no way makes you less of a human being, less worthy of respect, less deserving of dignity. Homosexuals have contributed enormously to humanity, from the great artists Leonardo da Vinci and Michelangelo to present day entertainers like Lily Tomlin, Elton John, Freddy Mercury, and Ellen Degeneres, and a million more in between! Those who looked down on gays and lesbians are only revealing their own ignorance.


© Copyright 2002, 2009, C. George Boeree