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Homosexuality: Nature or nurture?
29 Jun 2008, 0005 hrs IST, Divya A,TNN


Experts say that all in all, as many as 1,500 different species of birds and animals are known to display homosexual behaviour.
Does homosexuality arise from nature or nurture? It's an argument that has raged around the world for a long time. But scientific research increasingly seems to be tilting the debate in favour of nature.

In case of male conjoined twins, if one is homosexual, the other is likely to show similar tendencies, although the same may not hold true in case of females. In 1991, Boston University psychiatrist Richard Pillard and Northwestern University psychologist J Michael Bailey found that in identical twins, if one twin was gay, the other had about a 50% chance of also being gay.

In 1993, Harvard-trained researcher Dean Hamer found that gay brothers shared a specific region of the X chromosome, called Xq28, at a higher rate than gay men shared with their straight brothers.

Shortly thereafter, Newsweek ran a cover story on the subject, 'Gay Gene?'. Then, in the midst of a landmark legislation battle in the state of Colorado which raised the question of whether homosexuality was normal, innate and unchangeable, a prominent researcher testified, "I am 99.5% certain that homosexuality is genetic."

In 1994, two Canadian researchers discovered a statistical relationship between the number of ridges on men's fingertips and homosexuality, contributing additional evidence to the theory that sexual orientation can be influenced by biological events that occur at conception or early in fetal life.

J A Y Hall and D Kimura of the University of Western Ontario examined the fingerprints of 66 homosexual and 182 heterosexual men, comparing the number of ridges on the index finger and thumb of the left hand with the number of ridges on the index finger and thumb of the right hand.

If the number of ridges on the index finger and thumb of the left hand exceeds the number of ridges on the index finger and thumb of the right hand, one's fingerprints are said to exhibit leftward directional asymmetry. Hall and Kimura found such leftward directional asymmetry in the fingerprints of 30% of their homosexual subjects versus 14% of their heterosexuals.

"Some may refute such theories but they essentially point to the fact that homosexuality is, to some extent, determined even before a child is born," says gay activist Ashok R Kavi, who runs Humsafar Trust.

"Another study has found that in case of males, if there is less testosterone (male hormone) secretion during the development stage, they may have some girlish traits, and could even be attracted to boys. Daryl Bemm, a psychology professor at New York's Cornell University, had propounded a theory that hormonal levels are the causes of homosexuality," adds Kavi.

Interestingly, zoologists have discovered that homosexual and bisexual activity is not unknown within the animal kingdom. Experts say that all in all, as many as 1,500 different species of birds and animals are known to have displayed homosexual behavior.

Researcher and author Bruce Bagemihl documented such characteristics among birds, mammals and insects in his book Biological Exuberance: Animal Homosexuality and Natural Diversity, published in 1999.

"No species has been found in which homosexual behavior has not been shown to exist, with the exception of species that never have sex at all, such as sea urchins and aphis. Moreover, a part of the animal kingdom ishermaphroditic, truly bisexual. For them, homosexuality is not an issue."

That was the verdict of Petter Beckman, academic adviser for the 'AgainstNature?' exhibit - an exhibition on homosexuality in animals in The Natural History Museum, University of Oslo, Norway to illustrate that it is not unnatural.

So, if homosexuality can be the result of genetics, and if it exists throughout the animal kingdom, logically it cannot be unnatural. But the Indian legal system thinks otherwise. As per section 377 of the Indian Penal Code, any intercourse which goes against the "law of nature" is illegal.

But what exactly does the term mean? Some would argue that it is adapted from the religious belief that intercourse that doesn't lead to procreation is unnatural.

But by that definition, apart from homosexuality, all other forms of non-reproductive sexual activities become unnatural, including contraception.

Says gay activist Lesley Esteves, "We are born this way, we are not perverts. People have to understand that it's not a matter of choice to get attracted to someone from the same sex or from the opposite sex. And it doesn't have only sexual connotations. The relationship between two people from the same sex could be equally romantic as that between a man and a woman. So classifying us as criminals and penalizing us under section 377 is very unfair to us."

An 18-year-old, who has "just discovered" his sexuality and found out that he gets attracted to "his types" more than to girls, says: "I am feeling very apprehensive about my future. If society and laws don't penalize someone born a eunuch, why are people like us singled out?"

I also read somewhere that the more boys you have in the family the more likely the younger ones are to be gay. Something to do with a male fetus being unnatural to a female so her body tries to reject the male fetus. The placenta protects the fetus to some extent but the more boys you carry the stronger the antibodies sent to attack. To survive, the baby must become more feminine.

Could be a load of rubbish... but only works for gay men. I've also read somewhere else that "gayness" in females is not attributed to genetics.

I think I have one of the articles on the ridge count and homosexuality. Will see if I can dig it out.

For those of you with access to the BBC and have an interest in this matter - John Barrowman (Dr Who, Torchwood) has a programme coming up exploring whether it's nature or nurture!

The Making Of Me airs on the U.K.'s BBC One on 24 July.

While this is a very interesting topic, there are a couple of things that should be pointed out.

The 1993 paper by Dean H. Hamer and his team, who thought they had located gene controlling male homosexuality failed to replicate their study. Other researchers have also tried to replicate this study unsuccessfully (ref. Bryan Sykes)

The study conducted by J A Y Hall and D Kimura in 1994 also found increased incidence of adextrality in homosexual men, but not in heterosexual men. Does this mean that children with no handedness preference have a genetic predisposition to not only homosexuality but also are eternally doomed to throw less accurately? (ref Hall and Kimura, Archives of Sexual Behaviour. Volume 24, Number 4 / August, 1995) I would also suggest that sample size may be an issue here.

While you are digesting the above statements and wondering about how handedness and throwing ability entered this forum...

In the mid 1990s, R Blanchard studied families in which there was a homosexual male child. He found that a gay man is more likely to have older brothers than older sisters. He also found that the probability that a male child will grow up to be gay increased by about a third for every boy born before him. Blanchard suggests that this effect may be caused by an immune response within the mother during pregnancy. I am assuming this is the study mentioned by EmmaC. According to other sources, more recent studies have shown that this effect only happens among right-handed brothers! Other studies have also indicated that this phenomenon can be almost entirely attributed to parenting and behaviour expectation.

Bryan Sykes also suggests that what may be happening in families where there are a lot of children all of one sex is an immune response (or some other mechanism) towards that sex not being born. With this theory out there Blanchards ideas seems slightly more open to challenge.

In my opinion and on purely genetic grounds, I don't like the idea of the gay gene since it is very hard to see how such a gene could have survived and spread among our ancestors. Genes that even slightly reduce their chances of getting passed on to the next generation have very short life-spans. One would imagine then, that a gay man would be having fewer children than their heterosexual counterparts and therefore failing to ensure the future of their genes.

Regardless of handedness, 1500 other species, throwing ability and ridge counts this is an area of research that has fallen off somewhat since the nineties. Using fingerprints to make generalising statements about race, age or sex have proven to be extremely problematic in the past. In my experience no one would ever make a definitive statement in court that the prints located, (on the window sill at the point of entry) were made by a male Polynesian aged 20 - 25 if that statement was based purely on the latent in front of them. I therefore seriously doubt the validity of recycling old studies claiming that ridge counts on (only) four fingers can account for homosexual, ambidextrous men that can't throw. Nor is it particularly useful to latent print examiners.

Nevertheless, an interesting topic.

a.

"In my opinion and on purely genetic grounds, I don't like the idea of the gay gene since it is very hard to see how such a gene could have survived and spread among our ancestors. Genes that even slightly reduce their chances of getting passed on to the next generation have very short life-spans. One would imagine then, that a gay man would be having fewer children than their heterosexual counterparts and therefore failing to ensure the future of their genes."

amy,
If there is a ‘gay gene’ it could be an autosomal recessive trait like sickle cell anaemia which has increased fitness when it is heterozygous compared to the homozygous dominate. A carrier of sickle cell anaemia has a resistance to malaria which increases their survival rate compared to the non-carrier homozygous dominate which helps to pass on the gene. So if a gene is selected against in one form (homozygous recessive), it may be able to survive as long as it is actively selected for in its other form (heterozygous).
Perhaps a heterozygous carrier of the ‘gay gene’ has increased hygiene abilities which reduces the likelihood of them contracting germs and diseases thereby increasing their (and the genes) survivability.
PG

Amy Weightman wrote:In my opinion and on purely genetic grounds, I don't like the idea of the gay gene since it is very hard to see how such a gene could have survived and spread among our ancestors. Genes that even slightly reduce their chances of getting passed on to the next generation have very short life-spans. One would imagine then, that a gay man would be having fewer children than their heterosexual counterparts and therefore failing to ensure the future of their genes.

It's probably not so simple as a "gay gene." Some genetic expressions do result in an inevitable or more or less high likelihood of an effect. If the effect is one that debilitates the carrier at an early age, it is indeed strongly discriminated against. But I suspect most of those pure effects die out quickly as simply incompatible with reproduction. But most of what survives either does not militate against reproduction (being of later onset, not debilitating, insufficient effect on early survival, etc.) or are more complex or are spontaneous defects, the tendency for which may or may not be inheritable. Genetic expressions that are only devastating in combination but are harmless individually will continue to be expressed. And a genetic expression that, viewed in isolation, might be seen as individually undesirable may contribute to the benefit of the group. A genetic tendency among breeding members of the group to have some offspring bearing a genetically based behavior may be a positive for the group when it contributes to stability. There's some evidence that male offspring are more likely to be gay as they are later male offspring of mothers bearing the larger numbers of male children. That would join the tendency to produce gay sons with the tendency to have more children. That sort of cancels the negative reproductive effect. It might even be that this linking of effects might work to mitigate potential overpopulation by taking some of the male children of high-volume mothers out of the game, or they may contribute to stability by relieving competitive stresses or reducing the necessity of breaking the group up too intensely as excess breeding males are driven out. And the ability to express sexuality male to male may allow outcast young bachelor groups to survive by hanging together until their members are needed to replace aging male herd leaders. Certainly a safer approach than the excess being asexual, which could leave the group survival vulnerable in hard times. (These things may be more fluid in animals without human cultural effects, and that complicates the devil out of simplistic studies of the sort that have been discussed here.) Evolutionary workings are probably far more complex than we can define. It may simply be that the benefits of genetic diversity simply makes it dangerous to entirely weed out every variation that doesn't happen to be clearly beneficial. A number of genetic expressions with more overt bad effects are found to provide immunities and other good effects.

While I agree with you that there's not likely to ever be much that can be definitively concluded from ridge count and that broad statements based on not very conclusive studies can be wrong, I try to keep open about anything that an expert can contribute. Things that cannot be relied upon as testimonial evidence may still be useful in terms of guidance. We become, pretty much by default, the folks with experience with hands and how they touch, push, and grip and how they make impressions. Without any particular reference to the present topic, we shouldn't be so hesitant to contribute only those things we can conclude with certainty that we won't allow all our knowledge and experience to be used.

Peter,

That is an excellent point, and one that I had considered. Phenotypic characteristics that present in homozygous, but not hetrozygous domninant genotypes, are very interesting particularly were disease resistance is in play. Social history could well make a very different arguement (?????)

Perhaps it is a combination of expression and the population stability mechanism that Gerald discusses. Maybe the 'gay-gene' is linked with population control? If, in fact, it was linked in this way it would still be an undesireable gene (ergo short lifespan) unless there is some incredibly intricate population dynamic well beyond my limited capacity in this area?

Who knows, it is a very complex field. Many more questions than answers.


"Things that cannot be relied upon as testimonial evidence may still be useful in terms of guidance."


In this instance I don't think the intel gained by knowing that a offender may or may not be gay is useful or relavent. Certainly not compared to an educated guess on race or sex or age. And best guesses in each of those areas have proved to be very hit and miss. How a gene is expressed, if at all, may have absolutely no relivance.

We may well never know.

a.