+1 for the links. Great answer even without the links though.

@Abe Thanks for pointing that out. I made some edits in that section to clarify.

It is overly simplistic to say that "sexual orientation is something people are born with". Like most things, the truth is complex, and there are both genetic and environmental factors. Here is a summary of both positions (note that they largely agree on the data but disagree on the interpretation; I don't understand why both "sides" don't just agree that there are major genetic factors as well as major environmental factors, which is what the data shows!): borngay.procon.org/view.answers.php?questionID=000019

Don't you think that whole gender identity thing is archaic, sexist and outdated? From the linked site: "Males want careers, females want to stay home", I know some feminists that would have a field day with that one (if field day means getting really mad)

@bobobobo: if you read more carefully, the describes "traditional gender roles". It then states that not everyone wants to adopt those roles.

@RexKerr It may be a simplification, but it's largely accurate. The data does not show that there are major environmental factors, and it certainly doesn't show that anything in particular that parents do causes a child to be gay, and it absolutely does not indicate that an 11 year old's sexual orientation can be changed by parental intervention. So in this context, I'm comfortable making the statement that homosexuality is something you are born with.

@philosodad - I am not aware of data showing that 11 year olds can be changed by parental intervention. However, the data mentioned by Byne suggests that there is a window when at least a modest difference can be made. (This doesn't mean that one can necessarily predict what will nudge things one way or the other, since people are both cooperative and contrary.) Anyway, when you get 30-50% rates among identical twins, it says there are major environmental factors. We just don't know what they are; it seems not to be the obvious "tell your son not to dress like a girl."

@RexKerr The data cannot rule out the possibility of some environmental factors. That isn't the same as showing that there are major environmental factors. Any stronger claim is based on a total misunderstanding of both the data and genetics. Given that we absolutely don't know what environmental factors might be in play or to what degree they have any effect, I'm comfortable saying that homosexuality is a genetic trait.

@philosodad - You're defining random fluctuations as "not environmental"? I guess that's okay, if a little non-standard. Otherwise, that which is not genetic is environmental. (This doesn't mean that you know what it is in the environment, or that it's at all obviously connected with the phenotype--maybe levels of stress hormones when 15 months old.)

@RexKerr I'm saying that as far as a parent is concerned, homosexuality is a genetic trait, because while we do know that environmental factors influence how genes are expressed, we have no idea what those factors might be in this case or to what degree they might have an effect. So from the point of view of the person asking this question, if their son is gay, their son was born gay and nothing that they did do or didn't do "caused" him to be gay and nothing that they do or don't do now will change that.

Even if environmental factors influence homosexuality, breaking your boy's legs because he likes ballet doesn't seem like a good approach to raising a happy child.

@philosodad - You're conflating two different issues: whether it is theoretically possible for parents (as part of the environment) to influence sexual preferences of their children, and whether we actually know how to deliver a particular influence. The answer to the latter is no. The answer to the former is probably to at least a modest extent, so language like "nothing they did do or didn't do 'caused' him to be gay" is probably false. You wouldn't say that parents giving drinks to their children in lead cups "didn't cause brain damage" just because they didn't realize lead was toxic.

@RexKerr We know that there are genetic factors that influence whether someone is homosexual or not. We do not know if any parental behavior whatsoever has any predictable effect on whether someone is homosexual or not. We do know that parents do not control every aspect of a child's environment, and therefore the exact same parental behavior, given the immense complexity of environmental factors, is going to have different effects, so no, nothing that a parent does or does not do causes their child to be gay, and certainly nothing they do after the age of 11 will change them.

@RexKerr and if you would like to discuss this further, I suggest we take it to chat. This discussion does not belong in this comment thread.

@philsodad - I'm happy to move to chat; I agree such an extended discussion doesn't belong here. I thought it would be quick and simple. It's baffling to me to see such a mix of correct statements and logically invalid/contradictory ones: "do not know" -> "certainly nothing they do"; "different effects" -> "nothing...causes". The only way I see that this "makes sense" is if you're afraid that although your advice about the right thing to do is supported by the current data, it's not supported incontrovertibly enough for your comfort.