How can homosexuality be hereditary?

General Questions
#1

Back in the Dark Ages when psychiatrists classed homosexuality as a mental illness, they attributed its existence to environmental factors – domineering mother, weak-willed father, etc. Nowadays everybody but open homophobes seems to have accepted the theory that homosexuality is an innate characteristic – you’re gay because you were born gay.

Presumably – perhaps someone can correct me on this point – INNATE in this context means HEREDITARY, something you got from your parents. But how can homosexuality be hereditary? True, homosexuals do sometimes have children, but they’re much, much less likely to do so than straight people are. If there were such thing as a “gay gene,” wouldn’t it naturally be bred out of existence in a few generations?

#2

WAG: the magic of recessive genes.

#3

While innate means (loosely) born with, it it not necessarily an indication of heredity: there could be various influences in the womb that shape development regardless of genetic predisposition. (Look up congenital.)

There is no uniform agreement as to the nature and cause of sexual orientation, at this time, so speculation regarding its origins will remain speculative until more facts are learned.

However, even the possibiltiy of hereditary/genetic links is not outside the realm of possibility. There are any number of altruistic actions expressed by various species to further the species without necessarily furthering the individual, and homosexuality (in which a provider of resources does not reproduce/procreate more consumers of resources) might fit into such a scenario, while the genetic origin of those altruistic impulses may be carried by procreating siblings of the homosexual individual and passed on to later generations where they will be triggered in other individuals. (These last comments are, of course, speculative).

#4

The scientific community still does not have a clear idea of what exactly causes a person’s sexual orientation. It could be genetic, it could be environmental, and one theory that’s come into play over the past decade is that it may be caused by elevated hormone levels in the womb during early stages of development.

cite:
http://www.cnn.com/2000/HEALTH/03/29/gay.fingers/

I’m going to include this last theory as an environmental factor. If sexual orientation is decided or partially decided by environment, it could easily exist no matter who gets what genes.

A question I’ve always wondered is do chemicals we are exposed nowadays (such as pesticides, cleaners, pollution) have any effect on orientation?

#5

I see I was beaten to the punch. To clarify my question: Does exposure by a pregnant mother to certain chemicals have any effect on the sexual orientation of the child?

#6

I think one should look at the animal kingdon as a whole. Many species show homosexual behavior. If you take religion out of the situation, one might conclude that some 10 or 15% of all animals [including humans]show an interest in Homosexcal activity. As far as what I have read there is next to nothing to suggest that there is a hereditary/gentic link or that it is passed down from generation to generation. You raise a interesting question and I am going to study up on it…more later

#7

Well, exposure to androgens in the womb certainly affects the development of male genitals. Far too much detail here, but look at the spike in testosterone in male fetuses at ~month 4. If that gets messed up, you can end up with a baby who’s chromosomal sex does not match their genital sex. The effects on behavior are far less well understood.

#8

I would also posit that human sexuality (or any critter’s sexuality, for that matter) is way too complex to be determined by a single gene. There may be 20, 50, hundreds of genes involved, for all we know. So while there may be multiple different combinations of these genes which influence orientation, substantial portions of these sets are likely to be shared with siblings, with perhaps one subset of (for example) 10 genes missing in the sib. So the sib, who’s straight because of those missing 10 genes, is a “carrier” for the other 50-90% of the “gayness” package, and may very well produce gay offspring if her spouse happens to be a “carrier” of the 10 genes she doesn’t have.

My WAG anyway. I’d also suspect that environment played a role somewhere, be it in early development or later on.

#9

I learned years ago, when I first slept with a lesbian, that human sexuality can’t be accurately described in black & white terms. Humans are complex, and I think people are gay for a multitude of reasons; sometimes it’s genetic and sometimes it’s for other reasons. I’ve read somewhere that the brains of (some) gay people & straight people are different - gay men’s brains are more like women’s brains, and vice versa. This would seem to explain why (some) gay men act (& look) like girlies and (some) gay women act (& look) like men.

#10

Loosely? Innate MEANS ‘born with.’

Dictionary.com obligatory reference:

1: Possessed at birth; inborn.

I don’t dispute your assertion about other influences, but I dispute your definition of ‘innate.’

Mozart, if you’re going to make a claim like this:

“If you take religion out of the situation, one might conclude that some 10 or 15% of all animals [including humans]show an interest in Homosexcal activity.”

You might provide some sort of corroboration or cite to back it up (and run a spellcheck).

I have NO axe to grind here and no relevant info to contribute to the OP, I’m just fighting the short fight against WAGs and hearsay.

FTR Tomndebb, you are one of my favorite posters (top 5!) and I’m not trying to start a pit war or anything. I have learned so much from you, you wouldn’t believe it - I just disagree with your usage in this instance.

#11

'salright. I don’t actually see a big difference. I threw in the “loosely” to head off any hijacks that wanted to dispute a meaning of “inborn” as not meaning “born with,” but if you want to assert that the meanings are identical, I am certainly not going to object. :wink:

#12

Don’t forget the “sickle cell” effect – a gene that has positive effects in one way may have negative in another, as in the gene where GG is normal susceptibility to malaria, GH (heterozygous form) provides increased resistance to malaria, and HH (homozygous form) causes sickle-cell anemia. (I’m not sure what chromosome it’s on; G and H are simply letters chosen at random to avoid the AB blood type or XY for sex-linked.)

One hypothesis I have, which has some logic going for it, is that the very normal thing of “male bonding” where two men are friends and companions, e.g., on a hunt, was selected for – and it could be that it’s the heterozous expression of what male homosexual orientation is the homozygous one of.

Since groups of males would be more successful than solitary hunters, it had biological survival value, and was selected for.

I make no claims to anything other than WAGitude for this. But it’s an example of why a “countersurvival” trait might be selected for.

#13

apparently more deaf men are gay. not to say there is a connection with deafness and homosexuality…but a deaf man is exposed to less gay bashing… gay jokes… etc etc, so possibly, he feels less pressure to be something he is not.

same thing with having homosexual parents. growing up with gay parents would probably help kids, at an early age, to accept who they are. To explore their sexuality more freely…without stigma… etc etc.
i dunno

#14

FWIW, and this isn’t a factual answer, really, but my father and his first cousin are gay, as am I. Didn’t help me any when I was coming out, but that’s the way it was.

#15

I know to men who are gay and deaf. And the answer is – nope.

#16

A couple scientists a few months back were researching the genetic link and found links to possible gene mutations causing it and such- if it was a random gene mutation it wouldnt need to keep getting handed down either. Their funding got yanked because the research wasn’t politically correct. I think thats how it went. I can’t provided any information on actually finding the study, sorry. I read it in The Week, though.

#17

Speculation: say the sex drive is a strong, innate and heredity force, but how it is expressed might be subject to variation due to pre-natal influences, gene combinations, etc.

Observation: I have observed homosexual behavior in dogs (male-to-male) and in cattle (female mounting other female when the second was in heat–there was no bull in the pasture).

So it is not just a human thing.

#18

I have mentioned the same thing.
Years ago, when I was living in Berlin, there was a study being done by students at the Frei Universitaet.
They found that there was a higher percentage of Gay men in the deaf community, and their theory was the same…the deaf Gay man had not heard all of the slurs his whole life.
This does not mean deaf men were all Gay, or oblivious to homophobic comments, but those who were able to grow up and decide their sexual orientation without social pressure were more inclined to be Gay than those who did hear the slurs.

#19

Aye Walloon… you don’t say.

errrrrr

#20

E.O. Wilson’s original answer to this question was: kin selection. That is, even if homosexuals don’t reproduce directly, those kin groups that have recessive homosexual individuals occasionally tend to do better and thus survive.

But there’s another head slappingly obvious possiblity to be factored in as well: gay people reproduce too. Perhaps not as much as heterosexuals, but especially before homosexuality was accepted, it wasn’t uncommon for homosexuals to have kids and families. Even today, plenty of gay couples arrange to have at least one partner “in” on bringing about a kid.

However, the stumper is whether children of gay people are any more likely to be gay themselves. When they are adopted children, this doesn’t seem to be the case. But I don’t know anything about biological children of one or more gay parent.