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A common biological basis for male homosexuality and male-to-female transsexuality?

 
 
Ganesh
13:29 / 05.11.02
Firstoff, a useful link summarising the wide range of differing theories postulating a biological basis for homosexuality. This is a pretty loaded area, both politically and emotionally, and almost every one of these theories has been seized upon, at one time or other, for use in someone's agenda.

The theory of most interest to me is the Maternal Immunity Hypothesis:

"The Maternal Immunity Hypothesis concerns the hormones of the mother of the homosexual individual, as well as the individual itself. Per this hypothesis, fraternal birth order shows the progressive immunisation of some mothers to Y-linked minor histocompatibility antigens (H-Y antigens) by each subsequent male foetus. H-Y antigen immunity influences future sexual orientation, by diverting the foetal brain from male-typical pathways. The question exists: could this differentiation exist without affecting genitalia differentiation?"

This theory is based on one of the few highly-reproducible research observations in this field:

"Sexual orientation correlates with number of older brothers: with each additional brother, the likelihood of homosexuality increases by 33%. Also, a high birth order is associated with homosexuality in men regardless of culture, demographic or psychological characteristics of subjects. Further evidence for this theory lies in sex ratios of homosexuals' siblings: the ratios of males to females in sibships of homosexual males matches or exceeds population norms. This ratio is congruent with the hypothesis of H-Y antigen immunity increasing, or staying the same, with each male son."

So it's as if each male child successively stacks the odds in favour of the next male child being gay - although the mechanism by which H-Y antigen immunity might exert such an effect on the foetal brain is frustratingly unclear.

What interests me is the advent of a more recent London study which found a similar phenomenon among male-to-female transsexuals: like homosexual men, they were more likely to be younger children and have a high ratio of older brothers. As in the homosexuality studies, this finding is not mirrored in female-to-male transsexuals.

All quite speculative, of course, but if the same (largely unexplained) biological mechanism were found to underly both male homosexuality and male-to-female transsexuality, what does this suggest? What are the implications?
 
 
Lullaboozler
13:48 / 05.11.02
Was going to post this in Headshop, but as Ganesh has started a very similar thread on the topic:

http://www.newscientist.com/news/news.jsp?id=ns99993008

Could this be (at the very least) part of a biological mechanism to explain male homosexuality? It does seem to correspond to the postulate that male homosexual's brains would share some characteristics with those of straight females.

As for the number of older brothers being a factor, all I can add to that is that both my cousin and I are the older brother of a pair and he is gay and I am bi. I know that two people don't prove a point, but the fact that we are related (our mothers are sisters) would back the biological/genetic explanation to some extent.

With regard to the social implications, I can't help but think of eugenics and the awful consequences of that. Society is not mature enough to be able to cope with the ability to screen out 'gayness' from a child. It is still seen as far too abnormal by too many people to not be one of the first things parents would want to screen for.

To paraphrase Ganesh, this would be used to push someone's agenda.

A bit busy here in work to fully formulate my thinking, but this is my general take on the matter.
 
 
Ganesh
14:05 / 05.11.02
Ah, the 'gay sheep' thing! ChristianBBS has been getting all a-lather over that one, perhaps illustrating the 'political agenda' point.

Personally, I'm rather sceptical of these sorts of studies, partly because they infer "homosexual behaviour" among animals from things like same-sex copulation, and they imply an (IMHO) overly deterministic one-way link between neuroanatomy and behaviour when there's evidence that behaviour can also influence anatomy (can't recall where I read it, but a flippant example would be London cabbies' neuroanatomy altering to reflect having to learn The Knowledge...).

I find the birth-order stuff, which appears more readily-replicable, more convincing as evidence of a biological - if not genetic - link.

Anecdotally, it doesn't work for me either: both my partner and myself are eldest sons with two younger sisters - but there y'go.
 
 
grant
14:19 / 05.11.02
Well, one of the more alarming possibilities (and the first one that came to mind) is that if proved, this would suggest that homosexuality is a treatable problem, through some sort of prenatal hormone supplementation or some such. Not quite "Gattaca" but getting there.

If this was proved, it might also help reinforce the idea that homosexuality is something that happens, you know? It's really not a lifestyle choice or psychological complex, but something far more organic and complex.
 
 
Lullaboozler
14:33 / 05.11.02
Ah, the 'gay sheep' thing! ChristianBBS has been getting all a-lather over that one, perhaps illustrating the 'political agenda' point.

Hmm, link doesn't work - maybe they twigged it was you again Ganesh and deleted the thread. :-)

I am also sceptical of studies of this nature, it just felt like it fitted perfectly with your thread and abstract - common biological mechanism. I think that there is an awful lot of research still to be done in this area, but it will always be seized upon by one group or another. As you said in your original post, this is a pretty loaded area.

The birth order thing would seem to stand up more as the empirical evidence would seem to support it. Guess we're just freaks :-)

As for the whole biological/genetic thing, is not the former responsible for the latter? A biological mechanism would surely have its origins somewhere in the genetic structure of the individual/their parents - and then we could find ourselves going down the whole 'gay gene' things again.

Personally, it would please me if this was NEVER resolved. A conclusive cause (of either biological or environmental nature) would result in it being either screened for during pregnacy or 'parented out' by concerned parents.

I like feeling what I feel and wouldn't want to be any other way - especially if someone had made that choice for me during my gestation/early youth.
 
 
gravitybitch
14:45 / 05.11.02
So far, the "biological basis for homosexuality" theory that I'm most familiar with has to do with a gene that also happens to decrease the likelihood of a viable male fetus - those that survive tend to be gay, and there is a much higher ratio of female to male siblings...

It fits with the family histories I know well enough to analyze: my mother had only one brother, flamingly gay; I have only one brother, about a Kinsey 5.5; a gay friend has no brothers and his mother also has no brothers... (It will be interesting to see how my sister's children turn out...)

The theory is years old, and may have been thoroughly trashed by now; I didn't see anything like it in Ganesh's link and haven't done any research on the topic in about four years.
 
 
Ganesh
15:05 / 05.11.02
Lullaboozler: well, strictly speaking, the prenatal hormonal theories are not genetic but 'environmental' in that they are not directly defined by foetal genes but by maternal hormones exerting influence in the prenatal period.

If a definitive biological 'cause' could be established, the information could be used either by homo-sympathetic 'liberals' (touch of CBBS there...) to promote a rather disempowering 'illness model' of homosexuality - y'know, they can't help it, they're born like that. Alternatively, as Grant says, it could lead to some eugenic 'solution' to homosexuality (assuming prospective parents would want to screen it out).

In 'Gattaca', society seemed unusually stagnant, and I can't help but wonder about the possible cultural effect of completely eliminating all homosexuality, transsexuality (and other gender confusion / queerness?) It's near-impossible to imagine.

I can also envisage a potentially-stigmatising distinction being drawn somehow between 'true' homosexuals (those with whatever biological marker) and those who adopt a same-sex lifestyle (whatever that means) for 'non-biological' reasons...

The implication that male homosexuality and male-to-female transsexuality might share a common origin is potentially quite controversial and, in some ways, interests me more. The majority of MTF transpeople are insistent that they are not gay, and anecdotally, most gay men reject the idea that they are 'neuroanatomically female'. Strange political bed-fellows indeed.

(Oh, and the link's just a bit iffy. I've fixed it and am hoping a moderator will be along to fix it soon...)
 
 
Lullaboozler
15:42 / 05.11.02
the prenatal hormonal theories are not genetic but 'environmental' in that they are not directly defined by foetal genes but by maternal hormones exerting influence in the prenatal period

Ah, I see your distinction now - I was taking the stance that everything pre-natnal was genetic and everything post-natal would have to be environmental, which was me falling into a duality trap.

I seem to remember watching a Horizon (or similar) where the analysis of the brain structures of gay males/MTF transpeople were shown, and there was a correspondance in the size of certain parts of the brain between the groups - it may have even been the programme about the little boy who was raised as a girl due to a rather extreme circumcision accident (shades of the mutilation thread rearing its head again).

The upshot of this was to 'prove' that nurture could only go so far in determining gender identity (and possibly by implication, sexual preference) and that you are pretty 'hard-wired' from birth to be one thing or another.

Saying that, the recent human body series presented by Lord Winston had an episode where they followed the progress of an American woman who was taking male hormones as the initial stages to her gender re-assignment, and the corresponding brain scans/tests showed that after 6 months on the hormones hir brain had begun processing things in a more 'masculine' manner.

Ganesh, you can probably throw some light on my muddled recollections...

can also envisage a potentially-stigmatising distinction being drawn somehow between 'true' homosexuals (those with whatever biological marker) and those who adopt a same-sex lifestyle (whatever that means) for 'non-biological' reasons...

Only being able to be accepted by one side or the other if you could 'prove' your authenticity (or lack of)...

God! I had enough trouble coming to terms with my sexuality during the whole gay-chic thing a while back. I so did not want to look like a 'me-too' while I was working out who I was.
 
 
Ganesh
16:05 / 05.11.02
The 'botched circumsion' case is, I think, that of John/Joan Theissen, who became a patient of 1960s gender identity specialist John Money. The case was instrumental in illustrating the pitfalls of overemphasising a determinedly non-biological view of sexuality (unfortunately, he used the same case years earlier to illustrate his 'success' - a tad prematurely...).

The neuroanatomical stuff is interesting but remains ambiguous - needs a good deal of repetition to establish both validity and reliability. Unfortunately, with so many vested interests, the findings of even the smallest, dodgiest of studies is typically trumpeted from the rooftops...
 
 
grant
13:09 / 06.11.02
Weird - I got distracted from watching election results last night by a Nova program on the Winnipeg twins case. Bruce Reimer, botched circumcision (using heat to burn off the foreskin), surgically "fixed" and raised as a girl. Money used this case for PR because Bruce had a twin brother. Unfortunately, he didn't share any of the results after the twins' sixth birthday... about the time "Brenda" started feeling... wrong.
Lots of interviews with the tearful mom. And it was very dramatic when they finally interviewed "Brenda" - who is now living as "David," and has a wife and (I'm presuming step-)kids.

The show has a very good website here.
It includes the first person story of an intersexual not included on the broadcast.
Max Beck:
After five weeks of study and surgery, they weren't any closer to the truth; mine was a fuzzy picture. Not even the almighty gene provided any clear answers, since it was discovered that I was a mosaic, with some cells in my body having the XY genotype and others having XO. The decision was made to raise me female.

Could my parents do that? Could they ever hope, after all they had been through, to "raise me female?" What sort of instruction is that anyway?

"Feed the baby every two hours, burp well after feeding, and raise it female."




I also liked this passage:
Tomboy, unfinished girl, walking head, Frankenstein, butch -- these were all just so many wonderful/terrible, sharp/ill-fitting suits; the body wearing them was and is transgendered, hermaphroditic, queer. And an important, even essential element of that queerness was the trauma that accompanied it, the medicalization, the scars, the secrecy, the shame. I was born a tiny, helpless almost-boy, but the way my world responded to me is what made and makes me intersexed.

In March of 1998, after over a decade of therapy, I decided to switch to testosterone and transition to male. Since 1996, I had been an active part of the intersex community, and by deciding to transition, I thought I was copping out. I felt like a deserter, a coward, fleeing the frontlines of the gender war. As a politically aware intersexual, I felt it was my duty to be as brazenly androgynous, as visibly hermaphroditic as possible. But to return to the body/suit metaphor, I was starting to feel very naked and very cold. My "naked" body was scaring little old ladies out of public restrooms, making seemingly simple tasks, such as shopping, surprisingly difficult.


More pertinent to this thread, however, would be this page on fetal gender development.
 
 
Sleeperservice
18:58 / 08.11.02
Interesting. The parental hormone theory, while enviromental from the foetuses point of view, could still be genetic if the higher testosterone levels (I think that's right) are the result of a gene passed down the female line producing the altered hormone levels.

I read a report in Newscientist a while back about this theory which said higher testosterone levels in the womb increased the chances of the baby being gay, left-handed and having musical ability (yes really ). I'm gay (& right-handed), my brother is left-handed (& hetro) and we're both musically inclined.
 
 
grant
19:54 / 08.11.02
The thing that's been at the back of my mind on this issue (and I've been thinking about it probably more than is healthy over the last few days) is that there are known environmental pollutants that mimic (some of) the effects of hormones - things like pesticide and shampoo additives.
I mean, at this point, the science is pretty light on the ground, but what if it wasn't a "lifestyle choice," and it wasn't genetics, but it was Monsanto and Procter & Gamble?
 
 
Ganesh
20:15 / 08.11.02
Interesting angle, but how would that tally with the birth order stats?
 
 
pointless and uncalled for
10:34 / 09.11.02
An interesting page and while I can't claim to understand all of it I think these theories are very eye opening.

On a more eejit level, what happened to the homosexuality caused by intercrossed XY, dominant and recessive gene sequences theory. I was under the impression that this was quite well accepted and it's interlinked degree of randomness was the explanation of percentage birthrate stats.

Back to the Q in the abstract, on a purely scientific basis I don't think that the implications are that great. This sort of information is easily and often relagated to the level of another thing that we know and filed in thesis until the mechanisms either fall under question or become relevant to an alternate study.

However there are, I think, wider ranging implications on a intersocial scale. If the theories are correct then this could become an influencing factor on birth patterns and medical practices in relation to pre-natal and preparatory-natal practices and operations. In addition to that there are the further arguments related to discrimination and social applications at administrative levels.
 
 
The resistable rise of Reidcourchie
15:56 / 09.11.02
I've got a funny feeling that I'm about to make a full of myself. If I offend anyone please be aware it is through ignorance not prejudice.

Recently C4 ran a programme called Sex BC, one of which was about ancient Athens. Now I know the programme's validity has already been called into question over on Haus's thread and I really don't know very much about the period, however it suggested that at one period within the cities period that males prefferred to have recreational sex with other men whilst women where expected to stay out of sight in the house and sex with them was joyless act purely for procreation.

The programme seemed to suggest that this idea was adopted pretty much unviversally by upper classes, specifically in a burgeoning gymnasium culture and provided for by other classes in the sex industry.

If this was the case how would that effect a biological explanation of homosexuality? Would it just have been more likely to have happened for some reason in this area? Or was their sexuality heavily effected by societal/cultural factors, the lifestyle vs biology mentioned above? Or was this just a poorly researched and misleading programme?

How important is it to find a "reason" for homosexuality? It seems to change all the time (it's not that long ago that it was considered a mental illness) and always seems to open up suggestions that it can be either cured or eliminated?
 
 
Bill Posters
13:55 / 10.11.02
If this was the case how would that effect a biological explanation of homosexuality? Would it just have been more likely to have happened for some reason in this area?

Well, OTTOMH, and admittedly knowing little about gene pools, I see no reason why a certain gene pool couldn't house a lot of 'gay genes', if such things were to be shown to exist. I'd guess one would have to think about whether these allegedly exceptionally gay Athenians had a limited gene pool or whether they were interbreeding with half the world at that point.

Or was their sexuality heavily effected by societal/cultural factors, the lifestyle vs biology mentioned above?

Well, there's another explanation that homophobic societies need a high birth rate, homophile societies need a low birth rate. That being ecological rather than biological, strictly-speaking, and not necessarily having much to do with genes. I believe there's a Melanesian lot who ban heterosexuality on 268 days of the year. Our own Mr Disco spent some time living amongst them, before unwisely attempting to mould Barbelith to a similar social form.

I'd have thought the psychoanalytic angle could use the sibling thing to its own advantage. As could Lorenzians... if there are lots of older boys around, is a boy more likely to be 'imprinted' with a male-seeking sex orientation? (Does anyone use 'imprinting' these days or is Lorenz hopelessly OOD?)

As for the societal-cultural side, that too can be used to account for much of it, in various different ways. The category 'homosexual' did not exist around a hundred years ago, and certainly not in ancient Athens.

Finally, am I the only one to be amazed at the description of homosexuality as "depravity" in that link?

Oh and finally finally, what about dykes? Have no comparable patterns been mooted to explain lesbiological behaviours?
 
 
Lurid Archive
00:15 / 11.11.02
I've been wanting to rant about science and morality for some time now. So, if I may answer the question

Birth-order and sibling studies indicate common findings for male homosexuals and male-to-female transsexuals. If a common biological mechanism underpins both conditions, what are the implications?

rather too literally, I'd say that the implications are marginal. It is fascinating from a science point of view but, as Ganesh says at the start of the thread, these ideas have been adopted by all sides. Our feelings and morals about homosexuality and transexuality do not derive from the biological processes that may (or may not) enable them.

I may be missing the point of the thread (which I'll be happy to re-engage with later on) but I think it important to point out that it is behaviour and emotion that determines our outlook, not some appeal to genes or embryonic development. People are queer. People are transexual. And it is wrong to try to browbeat them into being "normal". End of story.

As Bill points out, our understanding of the relationship between biology, nature and culture is debatable to say the least. This might be a short sighted (and quite powerful) argument to deploy in the face of prejudice. But I think we should always keep in mind where the line really is.
 
 
grant
15:32 / 11.11.02
Interesting angle, but how would that tally with the birth order stats?

Well, how do normal hormonal levels tally with birth order?
Maybe it's some sort of reservoir effect - either something is depleted or something is built up.

I don't know - I don't think the research exists, and if it does, I'm not sure where to find it.
 
 
grant
17:12 / 14.10.04
The latest New Scientist has a heredity study that finds the same gene -- sorry, genetic factors -- that cause homosexuality in males makes women hyper-heterosexual. "Excessive fecundity" is the phrase they use.

The study, in summary:
Camperio-Ciani's team questioned 98 gay and 100 straight men about their closest relatives - 4600 people in total. They found that female relatives of gay men had more children on average than the female relatives of straight men. But the effect was only seen on their mother’s side of the family.

Mothers of gay men produced an average of 2.7 babies compared with 2.3 born to mothers of straight men. And maternal aunts of gay men had 2.0 babies compared with 1.5 born to the maternal aunts of straight men.



There's also some analysis of the significance of all this.


Their findings also support earlier findings that when mothers have several sons, the younger ones are progressively more likely to be gay. This might be due to effects changes to the mother’s immune system with each son they carry.

But Camperio-Ciani calculates the contribution of this effect to male homosexuality at 7% at most. So together, he says, the “maternal” and “immune” effects only account for 21% of male homosexuality, leaving 79% of the causation still a mystery.

 
 
Our Lady Has Left the Building
10:31 / 15.10.04
Evolution's Rainbow argues that non-binary modes in gender and sexuality are so common in the animal world that there's not much point in looking for a agenetic basis for homosexuality as though it were an abheration.
 
 
Ganesh
11:09 / 15.10.04
Well, there's certainly no point in looking "as if it were an aberration" but I think it's still a worthwhile exercise. Personally, I suspect the agenetic element (up to 21%?) might have more of an effect on the degree of expression of more 'hardwired' factors...

Incidentally, I bought Joan Roughgarden's book a while ago but have yet to sit down and read it properly. Would you recommend it, Flowers?
 
 
Our Lady Has Left the Building
09:29 / 20.10.04
Is agenetic a word then? I mistyped genetic...

I did enjoy the book, she gets her ideas across in a way that the non-scientifically minded like me would understand. Whether that lack of knowledge and/or wanting her ideas to be right means there's some huge flaw in her thesis that I didn't spot I don't know, but it gave me a possible reason as to why Dawkins and Blackmore's memes might exist (if you accept they do exist), I'm not sure biological advantage is a Darwinian evolutionary reason for why animals tend to congregate in groups. She doesn't, IIRC, explain in her theory about the animals where one or both parents die in the mating/birthing process, such as insects which eat their partners...
 
 
Ganesh
10:48 / 21.10.04
I'd assumed you were using 'agenetic' to mean those biological factors other than genetic ie. hormonal influences, etc. But just a type? Oh well...
 
 
Bill Posters
15:30 / 23.10.04
The 'botched circumsion' case is, I think, that of John/Joan Theissen [...] The case was instrumental in illustrating the pitfalls of overemphasising a determinedly non-biological view of sexuality (unfortunately, he used the same case years earlier to illustrate his 'success' - a tad prematurely...).

Just for the record, sadly, Thiessen took hir own life, earlier this year ( i.e. in May 2004). The link in question explores hir many possible reasons for so doing.
 
 
Ganesh
10:53 / 24.10.04
Yeah, very sad indeed.
 
 
grant
16:15 / 05.11.04
Hey, there's something new* down the pike that supports a genetic factor passed down from the mother -- on the chromosomal level. It's in the way chromosomes are turned on and off by chemical signals in the body. In women, one or the other of the two X-chromosomes are "inactivated" or turned off by these chemical signals.

Dig the New Scientist:

Normally, this process is random; either of the X chromosomes can be inactivated.

But when Sven Bocklandt of the University of California, Los Angeles, compared blood and saliva samples from 97 mothers of gay men with samples from 103 mothers without gay children he found this process was extremely skewed in the mothers with gay sons, with one X chromosome being far more likely to be inactivated than the other.

...Mothers might not be resetting their own “I like males” program, he told a meeting of the American Society of Human Genetics in Toronto last week.



In other words, gay sons are inheriting their mothers' genetic program to seek out male mates.

*at least I think it's new.
 
 
Red Concrete
20:10 / 09.04.07
This is an old thread, but certain people might benefit from reading over it. I will also read it, collect some up-to-date links, and be back later.
 
  
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