Has it been proven that homosexuality is genetic?

[Coito ergo sum]

If yes, on what basis do you make that assertion? What's your evidence?

[don't read anything into this question - I am not of the opinion that homosexuality is a choice - it doesn't feel like a choice to me, since I am not homosexual and I have a hard time imagining how I could feel about men the way I feel about women - but that's all beside the point - I am curious if this has been proven. The little research I have found is not conclusive, and has not shown that there is a genetic or heritable trait of homosexuality - I was wondering if I was missing something]

[Xamonas Chegwé]

Perhaps I could answer if you took the word 'believe' out of all of the options. No opinion I would hold on the matter would be based upon belief.

As I understand current thinking, there is some evidence for a genetic component but nothing as simple as a 'gay gene'. A combination of multiple genetic and environmental factors seems the most likely.

[Thinking Aloud]

Just found this newspaper article from 2004 ... Perhaps the source of this would reveal more.

Maternal genes, family size linked to homosexuality
(Agencies)
Updated: 2004-10-13 09:07


Genes handed down by one's mother and having a large number of older brothers may determine whether someone is a homosexual, according to a study published. [AFP]
Genes handed down by one's mother and having a large number of older brothers may determine whether someone is a homosexual, according to a study published.

Put together, these two factors may account for perhaps 20 percent of the prevalence of homosexuality, although social and cultural influences probably make up most of the rest, it suggests.

Psychologists at the University of Padova asked 98 homosexual men and 100 heterosexual men in northern Italy to fill out a confidential questionnaire detailing their sexual orientation and that of their siblings, first cousins, parents, aunts, uncles and grandparents.

Among the homosexuals, 22 out of the 396 male relatives on the maternal line of their family were gay, as were 12 out of 593 on the paternal side.

Among the heterosexuals, none of the 370 male relatives on the maternal line was gay; on the paternal line, the number was eight out of 604.

Just as striking was the relationship between birth order and sexual orientation.

In large families, homosexuals were likelier to have been born second, third, fourth or later, and were far likelier to have older male siblings rather than older sisters.

The study, led by Francesca Corna, says this adds statistical support to hypotheses about possible genetic causes for homosexuality, although it did not investigate homosexuality in women.

Previous research, carried out among gay brothers, suggests a link between homosexuality and a genetic sequence called Xq28 on one of the arms of the X chromosome, one of the chromosomes that determines sex.

Men have an X chromosome, which comes from their mother, and a Y chromosome, from their father. Women have two X chromosomes, one from each parent.

Research published in the mid-1990s bred the theory, strongly contested by some, that the male foetus presents an antigen, a molecule that triggers a response from the woman's immune system.

With each successive male birth, the mother is successively immunised against this antigen and the subsequence chemical change in the uterus has an effect on the sexual differentiation of the foetus, according to this idea.

An architect of this hypothesis, Canadian scientist Ray Blanchard, has calculated that each additional older brother increases the odds of homosexuality in the next male by some 33 percent.

Corna's team stress that cultural and social factors, in addition to genes, also powerfully shape sexual orientation.

"Over 79 percent of the variance in male sexual orientation, in our sample, remains unaccounted for by the factors of excess of maternal homosexual kin and number of older brothers," they note.

They wonder if childraising traditions in northern Italy could help mould sexual orientation and behaviour. Aunts, mothers and grandparents spend lots of time with the child in his young formative years.

"Our findings, if confirmed by further research, are only one piece in a much larger puzzle on the nature of human sexuality."

While acknowledging that the Nature versus Nurture debate about homosexuality will continue to rage, the authors believe they may have resolved one of the enigmas about homosexuality.

This is the so-called Darwinian paradox: if homosexuality is conferred in part by genes, why haven't these genes been progressively eliminated over the millennia by natural selection -- the process that prefers genes which are useful for reproduction and survival?

The answer could lie in Xq28, for the mothers of homosexuals could be exceptionally fertile.

In other words, this particular genetic variation is a Darwinian tradeoff -- there is low or zero fecundity among men because they are homosexuals, but high fecundity among women.

The study appears in Proceedings of The Royal Society B, a journal published by the Royal Society, Britain's leading scientific association.

(Article from http://www.chinadaily.com.cn/english/do ... 381937.htm )

[Coito ergo sum]

Perhaps I could answer if you took the word 'believe' out of all of the options. No opinion I would hold on the matter would be based upon belief.

Well, most of us do have things we believe. Like - I believe the sky is blue, and I believe that because it is proven. My answers, I think included all possibilities - including "no, I don't believe it is genetic." So, if you don't believe it's genetic, then that would be your answer. But, I'm going to change it to "think."

As I understand current thinking, there is some evidence for a genetic component but nothing as simple as a 'gay gene'. A combination of multiple genetic and environmental factors seems the most likely.

Link? Source?

[Xamonas Chegwé]

Perhaps I could answer if you took the word 'believe' out of all of the options. No opinion I would hold on the matter would be based upon belief.

Well, most of us do have things we believe. Like - I believe the sky is blue, and I believe that because it is proven. My answers, I think included all possibilities - including "no, I don't believe it is genetic." So, if you don't believe it's genetic, then that would be your answer. But, I'm going to change it to "think."

As I understand current thinking, there is some evidence for a genetic component but nothing as simple as a 'gay gene'. A combination of multiple genetic and environmental factors seems the most likely.

Link? Source?

The article that Meeky just posted will do for a start. I have read similar things here and there - I am pretty sure there was an Horizon program about it recently too. It's not a subject that I have any more than a passing interest in, to be honest - certainly not enough to keep a stack of references handy. That's why I qualified my statement with "as I understand" - because it is based on articles that I have come across but I can't be arsed to go and find.

[Thinking Aloud]

The article that Meeky just posted will do for a start.

[klr]

The article that Meeky just posted will do for a start.

Ouch.

I don't like the poll options as currently formulated, because they reduce it to a simple black/white dichotomy both in terms of causality (nature v. nurture), and "proof" (there is proof/there isn't). Not to mention a third implicit dichotomy: What counts as "homosexuality" and what doesn't.

[The Curious Squid]

I picked the not a clue option because I think there can be both genetic and psychological factors involved with homosexuality and the poll doesn't reflect that. I think that's what XC was saying too?

[Trolldor]

What else could it be but biological?

[JimC]

What else could it be but biological?

Well, thats a bit general. There could be absolutely no genetic component, but some environmental influence (in the womb or later) makes a real change to some aspect of brain functioning, and you have a tendency to become gay... In the broadest sense, everything about humans is "biological"

I certainly recall reading articles in NewScientist quoting research that suggested a genetic component to becoming homosexual, but I couldn't give you chapter and verse...

Whether it is or is not, one thing is crystal clear - god-botherers and governments can stay the fuck away from people's bedrooms...

[Elessarina]

Whether it is or is not, one thing is crystal clear - god-botherers and governments can stay the fuck away from people's bedrooms...

Barack Obama doesn't have to stay away from mine...

[Tigger]

Whether it is or is not, one thing is crystal clear - god-botherers and governments can stay the fuck away from people's bedrooms...

Barack Obama doesn't have to stay away from mine...

He's 48

[Elessarina]

He's 48

There are a couple of exceptions

[Gawdzilla Sama]

If yes, on what basis do you make that assertion? What's your evidence?

[don't read anything into this question - I am not of the opinion that homosexuality is a choice - it doesn't feel like a choice to me, since I am not homosexual and I have a hard time imagining how I could feel about men the way I feel about women - but that's all beside the point - I am curious if this has been proven. The little research I have found is not conclusive, and has not shown that there is a genetic or heritable trait of homosexuality - I was wondering if I was missing something]

Not being snarky here, but are you gay?

[Martok]

I've known a few gays who were raised in ultra conservative families and they knew they were "different" when they were very young.