Brain Scan

Via Andrew Sullivan new research on the neurobiology of sexual orientation:

The scans reveal that in gay people, key structures of the brain governing emotion, mood, anxiety and aggressiveness resemble those in straight people of the opposite sex. The differences are likely to have been forged in the womb or in early infancy, says Ivanka Savic, who conducted the study at the Karolinska Institute in Stockholm, Sweden. "This is the most robust measure so far of cerebral differences between homosexual and heterosexual subjects," she says.

Previous studies have also shown differences in brain architecture and activity between gay and straight people, but most relied on people's responses to sexuality driven cues that could have been learned, such as rating the attractiveness of male or female faces. To get round this, Savic and her colleague, Per Lindström, chose to measure brain parameters likely to have been fixed at birth. "That was the whole point of the study, to show parameters that differ, but which couldn't be altered by learning or cognitive processes," says Savic.

Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse. But, of course, as we see here these are related issues.

Comments

"Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not... But, of course, as we see here these are related issues."

I don't really think there's any inconsistency here. I'm pretty sure most Liberals, even the folks who like to talk about how "sexuality/gender is a construct", recognize that the "gender difference" in who men and women are attracted to is in fact mostly determined by genetics. It's not really inconsistent for me to think that gay men and women being attracted to men is genetic, while gay men and women liking tight jeans is social.

Posted by Sam L | June 17, 2008 12:24 PM

Sam L: sure, but "emotion, mood, anxiety and aggressiveness" are a bit more fundamental than jean choice. The idea that gender norms are at least somewhat biologically determined really is a pretty uncomfortable idea for many people.

Posted by Tom | June 17, 2008 12:32 PM

Sam, according to the researchers, this test did not measure brains reacting to sexual stimulus or related functions. It involved more fundamental brain activity involving mood, anxiety, etc.

Posted by Ryno | June 17, 2008 12:33 PM

In fairness, there are some conservatives who would find the hard-wired gay brain theory quite acceptable because this could also be the case for pedophiles and animal rapists, etc.

While that's probably a smallish contingent, generally speaking I'm sure the goal posts could easily just get pushed a little further no matter what scientific research is presented. Ridiculous agendas like the anti-gay one are rarely falsifiable with reason.

Posted by Brent | June 17, 2008 12:33 PM

I was under the impression that research indicated sexual orientation and homosexuality were the result of environment; namely embryonic development, and that it is the result of interactions between the fetus and the mother in utero. Therefore it would be neither genetic nor a "lifestyle decision".

Posted by freddiemac | June 17, 2008 12:37 PM

I think the these scans put a visual representation to something most of us already possess: Gaydar.

And it's primarily the social cues that set it off. So while liberals may prefer a genetic explanation in a theoretical/academic sense, in the real world we take the overlap for granted.

Posted by Geoff | June 17, 2008 12:43 PM

In fairness, there are some conservatives who would find the hard-wired gay brain theory quite acceptable because this could also be the case for pedophiles and animal rapists, etc.

The issue I have with these conservatives is that they conflate behaviors that have victims with behaviors that don't. "It's OK to be gay as long as you don't act on it" is a common position, but drawing a moral equivalence between the behavior of two adults and the abuse of a child requires a certain type of twisted brain.

One ridiculous argument I've heard directly from a fundamentalist is that if alcoholism has a genetic component, does that make it OK? Only a fundamentalist could make the self destruction of one's brain and liver equivalent to a long-term loving relationship that strengthens both people involved.

Posted by LFC | June 17, 2008 12:43 PM

I've always thought that the developmental story was more or less irrelevant to the moral question for reasons Brent gestures at. I'm lazy and I don't really see that I have some big excuse for that depending on whether that inclination of mine has some genetic or developmental origin. There is of course a big philosophical question here about responsibility here, but basically we've always known that we're subject to a variety of moral infirmities, and I don't see how whether something counts as a moral infirmity could be settled by discovering that the disorder is somehow really congenital.

Posted by Brendan | June 17, 2008 12:46 PM

To a certain degree liberals see gender-difference as constructed (and differences have certainly been exaggerated due to construction), but I'm not sure that liberals see gender identity as necessarily being constructed but rather the labels we place on those identities. Or perhaps more clearly, that a transgendered boy acts in ways we call feminine is not the result of social construction, but that we classify his behaviors as feminine is constructed.

Posted by Erik | June 17, 2008 12:53 PM

From yesterday's news -

"Overall, the environment shared by twins (including familial and societal attitudes) explained 0-17% of the choice of sexual partner, genetic factors 18-39% and the unique environment 61-66%."

Mostly unique environment. Not how you're raised. Probably biological, but mostly not genetic. Obvious enough, when you consider that a homosexual man's identical twin has a 75% chance of being heterosexual.

Posted by g | June 17, 2008 12:53 PM

I'm sure the goal posts could easily just get pushed a little further no matter what scientific research is presented.

See also: Global warming, "intelligent design."

Posted by Persia | June 17, 2008 1:02 PM

The issue I have with these conservatives is that they conflate behaviors that have victims with behaviors that don't. "It's OK to be gay as long as you don't act on it" is a common position, but drawing a moral equivalence between the behavior of two adults and the abuse of a child requires a certain type of twisted brain.

Right, and the incredibly vague argument a lot of fundies end up coming back to is family destruction and children going wacko and so on. Nevermind that there isn't a shred of evidence of that homosexuality and homosexual marriage actually harms anyone. No, they continue to shout about how awful and immoral everyone is these days and for which homosexuality is just another cause. Again, nevermind the faulty premise or absence of causality for that one, either.

The point I'm really getting at is that most of the anti-gay stuff is irrational and/or unreasonable. You can't have a smoking gun when the other party refuses to engage in reality.

Having said all that, I do believe there's a nontrivial segment out there that answers all the poll questions reliably anti-gay, but also probably hasn't thought through the issue much (if at all) and their superficially achieved position is hardly irreversible in a way that the sentiment of the above-mentioned crazies certainly is. My feeling is that the hardliners are probably outnumbered by this relatively apathetic majority within the right.

Posted by Brent | June 17, 2008 1:03 PM

The whole concept of nature versus nurture is antiquated anyhow. The human mind is plastic, but many epigenetic changes arising during development are permanent and irreversible.

Posted by Joel | June 17, 2008 1:16 PM

The point I'm really getting at is that most of the anti-gay stuff is irrational and/or unreasonable.

I'm part of a mixed race couple. Just a few decades ago, it was illegal for us to be married in some states, like Virginia. The Mormons discouraged interracial marriage until recently. Bob Jones University just lifted their ban on interracial dating in 2000.

All the arguments the frothing right wingnuts make against gays (Biblical, unnatural, etc.) were all made about me and my wife not too long ago. Much to the radical right's dismay, bigotry based on both race and sexual orientation drop fast with the younger generations.

Posted by LFC | June 17, 2008 1:23 PM

Interesting stuff, but I notice the sample size was incredibly small, and included only 20 gay men and 20 lesbians. If they were recruited from a single bar then they are not a representative sample of much. (this is literally how that crank who is a disgrace to Northwestern University's psychology department find his gays to study)

You are not going to find any of the millions of "gender typical" gay men at a club that blasts Madonna remixes.

Drug safety studies requires 1000's or 10's of thousands of subjects, and political polls generally have 500+ people in them. Here, again, we have a study of just 20 people.

Sexuality is very complex and I think there are probably a variety of causes for a gay or bisexual orientation. Sexuality clearly isn't 100% genetic or 100% environmental, or even 80% of one or another. Some types of sexual attraction is about 100% environmental, for example to shoes, which didn't exist for 99.9% of human evolution. That is obviously a learned behavior.

Progressives lean toward genetic causes of sexuality because it provides us with an extra argument against gay discrimination and discredits the "change therapy" fundies. In the end, however, this argument is not needed because discrimination against gays is wrong even if it is in some ways a "choice." I am eager to see the results of larger studies.

Posted by Jim | June 17, 2008 1:28 PM

Eh. I've long figured that, given the significant variability in external sexual characteristics (hermaphroditism, mixed or undifferentiated genitalia, etc), it was probably likely that far subtler differences in the brain were even more common.

"Here, again, we have a study of just 20 people."

Brain imaging studies tend to be small, due to the need to get time on the big, expensive hardware. It's not like a drug study where the patients can just make an office visit once in a while and otherwise be followed by phone.

Also, drug studies are intended to demonstrate safety and efficacy, which requires larger samples. Brain research on primates is published that uses only 2 monkeys (that have performed thousands of trials of the experiment.)

I'm sure the study paper includes the statistics that show significance of the data given the sample size.

Posted by Jon H | June 17, 2008 1:45 PM

Or perhaps more clearly, that a transgendered boy acts in ways we call feminine is not the result of social construction, but that we classify his behaviors as feminine is constructed. - Erik

I dunno. This liberal generally figured that there were innate aspects of the brain that produced certain preferences in gender identification and gender attractiveness -- e.g. one could be genotypically XY but somehow have developed a brain structure that says "I shall identify myself as a woman" and a brain structure that says "I am attracted to women" ... or any such combination. However, this liberal also figured that many of the actual manners indicating femininity or masculinity or being interested in men or being interested in woman are socially constructed.

Thus, that I personally am genetically XY, identify as male and am into females doesn't really directly cause me to be a stereotypically straight male -- but that I identify as male and am into women causes me to pick up certain traits as the subconcious tendancy in social animals such as humans is to conform to what is expected given one's identity. Because I identify as male, I'll pick up male traits based on subconciously patterning my behavior based on males around me, etc.

Moreover, as Joel pointed out, brains are plastic -- that I may have a nucleus causing me to be attracted to women and a nucleus causing me to identify as male affects how I socialize myself in society. But this socialization affects my brain structure ... so just because I have a straight male brain, e.g., doesn't mean that I was born with that brain -- my brain itself could be shaped by society.

Which for social animals like humans, is not a bug, but a feature (call it liberal Lamarkianism if you will).

Posted by DAS | June 17, 2008 1:59 PM

Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse.

In other words, both liberals and conservatives tend to be extremely ignorant? Thank you for reinforcing my prejudices.

Posted by Jim W | June 17, 2008 2:02 PM

Note that the number of conservatives who think that sexual orientation is mutable is rather less than it might first seem because a lot of them use what in mainstream usage are orientation words ("orientation" itself, "gay", "homosexual", etc) to refer not to orientation ("I'm same-sex attracted") but to some confused mix of that, behaviour ("I habitually have same-sex sex.") and identity ("I'm a homosexual and the homosexual lifestyle is the right lifestyle for me.") In fact, NARTH says on its goals page ( http://www.narth.com/menus/goals.html ) that it promotes "teen awareness that homosexual attractions do not necessarily make one a homosexual."

Posted by Mark Barton | June 17, 2008 2:04 PM

They're doing it backwards. What they need to do is simply scan the brains of infants and then on every few years and THEN see which people turned out to be gay, like 30 years later. If there are structures that predict homosexuality from infancy on, that'd be pretty darn good evidence to go by.

Posted by Bad | June 17, 2008 2:11 PM

Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse.

To what degree are liberal "beliefs" not so much beliefs as what Ibsen would call "vital lies"?

I might not believe one way or the other about sexual orientation or gender differences (c.f. above for my actual beliefs), but I do think that the only just way to organize society is, in general, to ignore gender differences and to assume that gays are born that way.

Similarly, to what degree are conservative "beliefs" more "vital lies" than anything? To what degree do conservative beliefs reflect their own reality?

The few conservatives I know personally are the sorts of people who only feel comfortable when there are clear rules and boundaries on their behavior. They might not really believe in inborn gender roles at some level, but at another level they feel they have to believe in gender roles, because they are too uncomfortable without the guidance provided by "I am a man, therefore I can act [X] way and expect women to act [Y] way". Homosexuality is problematic for this kind of conservative because it makes things confusing for him: "how do I act when I am trying to make a friend so it doesn't seem to him that I am hitting on him?" They would just assume everyone is "naturally" straight (and homosexuality is some "disorder" that can be "cured") because it makes for simpler social rules.

And how many conservatives really do have very flexible sexualities or least perceive themselves as having such? We're always reading about some or other GOP politician who leads a double life ... how many such people, living as heterosexuals while still essentially being homosexuals, come to view their sexuality as something inherently malleable in a way in which I, as someone who wouldn't even think of making out with another guy, does not?

Posted by DAS | June 17, 2008 2:17 PM

As a liberal, I don't really care what causes homosexuality. I think gays and lesbians should be treated as individuals on their own merits, the same as everyone else, and should have the same rights as everyone else. Unless you think there's something wrong with homosexuality, I don't really see why it matters what causes it, or why our belief in what causes it would somehow skew based on politics.

As a point of scientific curiosity which might help answer other questions, I care. But as a political issue, I really don't.

Posted by Dave in NYC | June 17, 2008 2:18 PM

"Liberals tend to believe..."

Golly, I'm tired of being told what I think. Anyway, this liberal doesn't care why or how someone is straight or gay. I just don't care. Really. All I care about is whether or not someone wishes to pick my pocket or break my leg. Or someone else's.

Posted by Good2Go | June 17, 2008 2:39 PM

Unless you think there's something wrong with homosexuality, I don't really see why it matters what causes it, or why our belief in what causes it would somehow skew based on politics.

Fundamentally, I think you're pretty much right. My hunch is that those who believe homosexuality is immoral are reaching a bit when they try to use 'nurture' arguments (or others; like finding Bible passages that fit the conclusion) when in fact this doesn't really have much to do with how they feel about the issue in the first place. And not only do I think it's a tactical maneuver, I also think people somewhat subconsciously distract themselves from the knee-jerk reaction (like plain old-fashioned homophobia) they instinctively feel, but probably don't want to admit--even to themselves--that they do.

Still, I think it's useful to clearly show that these smokescreens are wrong anyway. Remove these things from the discussion and by process of elimination we improve the probability that social outcomes will get more focus in the debate and also within gay-bashers' own minds.

Posted by Brent | June 17, 2008 2:40 PM

Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse.

This sentence was obviously written by someone with no kids. Once you've had kids of both sexes, you'll soon come to the realization that there are huge, innate differences between boys and girls. Nothing wrong with that, but it just is. (Usual caveats about not all boys and girls, etc.)

Posted by Dave | June 17, 2008 3:40 PM

Determined by genetics?

Not even the number of my toes is determined by genetics. Genes turn off and on in response to clues from the greater environment. It's all a big swap meet/conference call.

Posted by Jeffrey Davis | June 17, 2008 3:49 PM

DAS: "The few conservatives I know personally are the sorts of people who only feel comfortable when there are clear rules and boundaries on their behavior. They might not really believe in inborn gender roles at some level, but at another level they feel they have to believe in gender roles, because they are too uncomfortable without the guidance provided by "I am a man, therefore I can act [X] way and expect women to act [Y] way". Homosexuality is problematic for this kind of conservative because it makes things confusing for him: "how do I act when I am trying to make a friend so it doesn't seem to him that I am hitting on him?" They would just assume everyone is "naturally" straight (and homosexuality is some "disorder" that can be "cured") because it makes for simpler social rules."

Wow. I'm not a political consevative at all, but I admit to feeling exactly this way about interacting with other people. The only hard and fast rules governing socialization still around only define the outer limits of acceptable behavior, but they provide no guide towards accomplishing some particular goal - like making friends, getting laid, etc. - within them.

That being said, ask any European and they'll tell you that Americans both liberal and conservative are absolutely obsessed with sex and sexuality. In their eyes, we attach sexual significance to so many behaviors that Europeans for example do not.

If this is a true characterization, then it would be difficult not just for rule-liking conservatives but for all people to engage in many activities, including and perhaps especially social ones, without some assumption of sexual identity or sexual motives being made not only those around them, but by themselves as well.

'Gay' after all isn't just same-sex sexuality anymore, but has acquired a whole galaxy of values and non-sexual behaviors that, perhaps unfortunately for straight people, are perceived both inside and outside the GLBT community as markers for 'gay'. Gays distinguish for example between gays and 'men who have sex with men': the first group identifies with the GLBT community and adopts to some degree the broader 'gay lifestyle', while the second group does not.

Posted by Visceral | June 17, 2008 3:57 PM

"Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse. But, of course, as we see here these are related issues."

The gay gene theory is fairly implausible because it's difficult to see how homosexuality could be an inherited genetic condition, since it's so disastrous from a Darwinian fitness point of view, and too common to be a simple genetic mistake like Huntington's disease. Greg Cochran's gay germ theory is an interesting alternative that gets around the Darwinian problems with the popular gay gene theory:

http://www.vdare.com/sailer/gay_gene.htm

Posted by Steve Sailer | June 17, 2008 4:39 PM

A couple of small caveats: Many areas is science don't require samples or statistical methods. If I cut off your head and you die, my colleagues are not going to ask for sample size. Most work in neuroanatomy is too 'basic' to require stochastic methods.
Second, I'm delighted to see my pet concept of 'constitutional factors' gaining some resepectability. There is much that is biological without genetics being involved. The brain grows itself, just as we all grow one another's brains.

Posted by Dick Mulliken | June 17, 2008 4:43 PM

At least of what respective groups tend to think are the causes, etc. of homosexuality have to do with the legal Civil Rights framework in our country. In a Civil Rights lawsuit, where a court tests the constitutionality of the government's interest in fostering discrimination against against an individual or group, the most protected class, the one that falls under "Strict Scrutiny" where the government is given the leasy benefit of the doubt, is that class where the members are defined by immuatable characteristics.

In other words, if someone wants to argue that homosexuals deserve to be discriminated against, et., they need to argue that it is "behavior" that is engaged in as a "choice". - Hence, those sorts of buzzwords and the occasional stir about gays being 'cured' if only they'd want to be. However, the easiest way to argue that homosexuals are a "protected class" and cannot be discriminated against without really very very good reasons, is to assert that as a characteristic it is immutable - via genetics, or something before birth and is an essental part of the person that cannot be changed.

This legal tension between the sides not only helps frame the discussion, but also ends up in political and policy differences, such as, conservatives are against adding attacks against gays to hate crimes laws, because that is one step along the way to recognizing gays as a "protected class".

Posted by Ethel-To-Tilly | June 17, 2008 4:44 PM

A couple of small caveats: Many areas is science don't require samples or statistical methods. If I cut off your head and you die, my colleagues are not going to ask for sample size. Most work in neuroanatomy is too 'basic' to require stochastic methods.
Second, I'm delighted to see my pet concept of 'constitutional factors' gaining some resepectability. There is much that is biological without genetics being involved. The brain grows itself, just as we all grow one another's brains.

Posted by Dick Mulliken | June 17, 2008 4:46 PM

"Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse."

Actually, lesbian-feminists have traditionally been highly dubious of biological explanations of homosexuality, in contrast to gay men, who have typically embraced them. Indeed, gay men and lesbians tend to differ strikingly on a tremendously wide range of traits, such as attitudes toward golf and perfume. For a list of three dozen traits on which gay men and lesbians tend to differ, see
http://www.isteve.com/lesvsgay.htm

Posted by Steve Sailer | June 17, 2008 4:46 PM

This liberal tends to believe that one's sexual preference, sex, and gender should not dictate one's rights, privileges, and opportunities. Why should it matter whether these traits are fixed or mutable, biological or sociological, none of the above or all of the above? So long as you don't harm beings who can't or don't give consent, your sexual and gender expression shouldn't limit your options.

Posted by AZ Escapee | June 17, 2008 4:49 PM

Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse. But, of course, as we see here these are related issues.

Sexual orientation is probably determined by genetics, or at the very least heavily influenced by genes.

What's odd here is that conservatives routinely cite biology as determining differences between the respective abilities of sexes and "races," but discard it when talking about gays...suddenly it's all dimestore philosophy about free will and choice.

Also:

Previous studies have also shown differences in brain architecture and activity between gay and straight people, but most relied on people's responses to sexuality driven cues that could have been learned, such as rating the attractiveness of male or female faces. To get round this, Savic and her colleague, Per Lindström, chose to measure brain parameters likely to have been fixed at birth.

Cute, since brain architecture of this type is constantly changing throughout life; people learn new things, which leads to new associations, new memories, etc, which leads to creating new pathways and strengthening certain ones already present. I have no idea what sorts of pathways are fixed at birth (beyond those designed for basic survival and learning skills); the brain is mostly tabula rasa at birth.

There's this and this.

Posted by Monty | June 17, 2008 4:50 PM

The gay gene theory is fairly implausible because it's difficult to see how homosexuality could be an inherited genetic condition, since it's so disastrous from a Darwinian fitness point of view - Steve Sailor

Do I dare (no pun intended) get Steve Sailor started with heterozygous advantage? Especially considering the classical example (Sickle Cell Anemia)?

Plus, this assumes that gays are 100% gay. Assuming partial penetrance (no pun intended) of the gene, many gay gene carriers might still go for an occassional romp of hetero-sex. And might be more successful at mating: how many women say "gee, I'd love to be involved with so-and-so, what a shame he's gay"? How many men say "wow -- two chicks ... that's hawt"? Someone who is pretty much gay but doesn't mind the occassional hetero romp might very well end up out-reproducing even a full-on hetero ...

Posted by DAS | June 17, 2008 5:29 PM

Do I dare (no pun intended) get Steve Sailor started with heterozygous advantage? Especially considering the classical example (Sickle Cell Anemia)?

No, because you would lose the argument. There's no analogy between teh SCA conferrence of protection to malaria vs homosexuality conferrence of protection to something else. There's zero evidence of homosexuality conferring protection against morbidity/mortality for an unrelated "disease." If anything, there's evidence of INCREASED mortality due to the easy transmissability of bloodborne diseases that occurs with the mucosal breakdown of the colon wall during anal sex.

Plus, this assumes that gays are 100% gay. Assuming partial penetrance (no pun intended) of the gene, many gay gene carriers might still go for an occassional romp of hetero-sex. And might be more successful at mating: how many women say "gee, I'd love to be involved with so-and-so, what a shame he's gay"? How many men say "wow -- two chicks ... that's hawt"? Someone who is pretty much gay but doesn't mind the occassional hetero romp might very well end up out-reproducing even a full-on hetero ...

The individual is irrelevant, only population dynamics supply sufficient coercion to influence gene pools. And on AVERAGE, its safe to assume that heterosexuals engage in more hetero sex, and therefore produce more offspring than homosexual or bisexual people.

Posted by joeblow | June 17, 2008 6:10 PM

Joeblow,

I didn't mean to make too close of an analogy with Sickle Cell Anemia. The heterozygous (or partial penetrance) advantage to having a gay gene need not be in terms of disease survival. If a gay gene made male proto-human apes more effeminate, they'd be able to cuckold the manly-man male apes while the manly-man male apes were out being manly-men and hunting or whatever. OTOH, while they were out there, a more masculinized female ape might be, um, there to join them, so to speak.

Gay gene carriers needn't outbread non-carriers for the gene to survive anyway -- they just need to bread enough to make up for fully penatrant homozygotes presumably not breeding much at all.

Moreover, human babies are incredably dependent on care-givers. If being gay is linked to nurturing behavior, gay gene carrying neices and nephews of gays would propagate.

IIRC, there has been work done on how/why a gay gene would propagate and it does work out ...

Posted by DAS | June 17, 2008 6:46 PM

Re: The gay gene theory is fairly implausible because it's difficult to see how homosexuality could be an inherited genetic condition, since it's so disastrous from a Darwinian fitness point of view -

It doesn't have to be inherited, nor does there have to be a single gay gene. Rather there may be gay genes, plural, with the trait only expressed if all of them have the right value. And if those genes have other useful functions individually they would not be winnowed out by Darwinian selection even if in combination with one another they limit reproduction. (Also note: historically at least most homosexuals and certainly most lesbians did in fact marry and produce offspring, if only because this was socially required).

Posted by JonF | June 17, 2008 6:59 PM

Dave, you beat me to it. And gracefully put.

Posted by Nat | June 17, 2008 7:24 PM

I'm too lazy to read the whole study, but my only concern would be that studying brain structures on a somewhat gross level might be inadequate to directly connect to behavioral influence. The brain is very complicated, and the interaction of genetics with neurochemistry and environmental influence is probably very difficult to assess with gross brain scans.

And, yes, sample selection would count here, given the wide variation in genetics in humans. People can vary up to 12% of their genes, IIRC. That's more than the difference between humans and chimps.

I agree with JonF that "Darwinian fitness" is not all-encompassing. Traits that would ordinarily result in the genes dying out if they were in isolation may exist simply for genetic variance reasons or because they have some other value.

Being gay obviously has some genetic value to the species because it continues to exist. Bi-sexuality clearly would have some genetic value, and we can't be sure how many "gays" statistically are really bi-sexuals socially conditioned to be homosexual.

Posted by Richard Steven Hack | June 17, 2008 7:27 PM

As far as the Darwinian connection and heritability of homosexuality, there's more than one way to skin that cat. For example, each male child increases the likelihood that the next male child in a family will be homosexual. The genes are on the QT to get successfully passed on and a helper in the family (instead of another breeder) would shorten those odds. We tend to view the individual as trying to spread his genes around, but it's useful to view the individual as simply the genes' way of spreading themselves around.

Posted by Jeffrey Davis | June 17, 2008 7:41 PM

I doubt that liberals, by and large, think that there's no inherent gender difference in behavior; rather, we object to the notion that such differences justify a patriarchal society. If there are liberals who deny the existence of the inherent gender differences altogether, it's probably due to the fact that they don't have kids yet.

Some examples from my own kids:

Daughter (at age 2 1/2): Let's play cars!
Mom: OK. Vrooom! Vrooom!
Daughter: No, no! Your car is the mommy car...

Son (at age 2 1/2, holding barbie doll): Look!
Cousin (age 3 1/2): It's a doll.
Son (pulling the legs off of the barbie, handing one to his cousin, then holding the other up): We can play swords!

Of course, this doesn't mean that their life choices have to be limited to traditional gender roles. It would be irrational, however, to suggest that there isn't an inherent difference.

Posted by Dan B. | June 17, 2008 8:10 PM

Dan B: I recall Jodie Foster saying something to that effect about her two boys. They started picking up "male" traits very early and she was quite bemused by it, wondering where they got it from (since there was no male in her household, aside from the late Randy Stone, a gay friend.)

Posted by Richard Steven Hack | June 17, 2008 8:25 PM

Steve, you forget that (1) identical twins are more likely to both be gay than fraternal (2) there is some evidence of a gay gene on the X-chromosome.

It must be some crappy germ too. My vote is part gene (in the sickle cell style) + reaction of mother's immune system.

Posted by JIm | June 17, 2008 8:40 PM

Nevermind that there isn't a shred of evidence of that homosexuality... actually harms anyone.

It's called AIDS. Maybe you've heard of it?

Being gay obviously has some genetic value to the species because it continues to exist.

Assuming that it is genetically determined. You're begging the question.

Bi-sexuality clearly would have some genetic value.

What?

Posted by Glaivester | June 17, 2008 8:42 PM

What Dave in NYC said.

What bothers me about studies like this finding their way into politics is that this is the wrong kind of empirical evidence upon which to hang an argument in favor of gay rights.

Whether sexual orientation is determined by genetics or by the social environment (or whatever) isn't relevant; what is relevant is whether sexual orientation is determined by an act of free will, i.e., whether it is a choice. If sexual orientation is not a choice--if it falls outside the scope of free will--then it follows that people should not be punished for their sexual orientation. And if a person has a gay sexual orientation and acting on it does no harm, then I think it follows that the person should not be punished for acting on that orientation.

So the relevant questions are empirical, though not really "scientific". They are questions about where being gay fits into our intuitive notions of free will and choice, and about whether gay behavior is harmful to society or not. And I think that those of us cosmopolitan enough to have known and interacted with gay people already have plenty of empirical data from personal experience that being gay is not a choice and that acting gay doesn't harm anyone, and that therefore there should be equal rights and privileges for gays.

Posted by David Morris | June 17, 2008 10:27 PM

I was surprised to learn that McCain comes down on the "liberal" side of this issue - he's said that he doesn't believe sexual orientation is a choice. He's also said that gay marriage is an issue for the states to decide, which Obama has said as well.

Does this mean Republicans won't try to use gay marriage as a wedge issue in 2008? Or does it mean McCain is due for another flip-flop?

Posted by TackyParker | June 17, 2008 11:22 PM

"Steve, you forget that (1) identical twins are more likely to both be gay than fraternal."

The concordance of identical twins for homosexuality is actually quite low. The last and best survey done by J. Michael Bailey of Northwestern, the leading demographer of homosexuality, using the Australian national twin registry found that when one male identical twin is gay, the other is straight 78% of the time. The great majority of identical twins were brought up side by side, so both nature and nurture are quite similar, and yet we get highly divergent results.

In summary, the causes of male homosexuality remain quite mysterious. It's one of the really interesting puzzles remaining. For a lot of the other questions about human nature, all we have to do is wait around for the genome data to pour in over the next 5 to 15 years, but this one may remain unsolved for some time.

Posted by Steve Sailer | June 18, 2008 12:12 AM

Glaivester: "It's called AIDS. Maybe you've heard of it?"

That's a virus which happens to be most easily transmitted through blood to blood contact, which occurs easily in homosexual sex. It has nothing whatever to do with homosexuality per se. It also is a relatively new disease historically speaking, and is therefore irrelevant to the overall question.

"Assuming that it is genetically determined. You're begging the question."

Not at all. Homosexual behavior is exists in many animal species. Presumably it exists in humans for the same or similar evolutionary reasons. And since it is unlikely to be a "choice" in lower animals, presumably it - or its underlying causes - are genetically determined.

"Bi-sexuality clearly would have some genetic value.

What?"

I'm not sure precisely what - merely that since the behavior remains, it presumably has some value. I also probably meant to say "evolutionary value" - which isn't quite the same thing even though the behavior - or its underlying causes - have to be passed on genetically.

Posted by Richard Steven Hack | June 18, 2008 1:46 AM

Steve this means having a gay identical twin means you have roughly 450% greater chance of being gay yourself, 22% v. ~4%.

And this is not the only study. Others have found ~50% and ~63% of the time the second identical twin is gay (or rather will fess up to being gay. A lot of these studies were published in the early 90's when the stigma of homosexuality is greater than it is now.

J. Michael Bailey is a well-known charlatan BTW. He goes to gay bars in a gay neighborhood in a big city as his source for gays to study, as if this were a representative sample. Wearing skin-tight clothing so he can "blend in."

No doubt about it, being a "demographer of gays" is a tough job since such a large number won't admit they are gay, and the precise definition of gay is not so clear. A tough job that Bailey isn't up to.

Posted by JIm | June 18, 2008 2:02 AM

Liberals tend to believe that sexual orientation is determined by genetics but that gender-difference in behavior is not, whereas conservatives tend to believe the reverse. But, of course, as we see here these are related issues.

Their relatedness has long predated this research. Studies of gay men and lesbians have provided important evidence for evolutionary psychological theories of gender differences. Those studies found that gay men are not "women trapped in men's bodies," as earlier folk-psychological theories of homosexuality commonly held, but rather men who share the same fundamental sexual psychology as straight men except that the objects of their desires are other men rather than women. Gay men's interests in promiscuity, pornography, prostitution and attractive young partners mirror those of straight men and differ substantially from the interests of lesbians and straight women.

But I agree with Steve Sailer that the causes of male homosexuality remain a mystery, although genes certainly seem to play an important role. And lesbianism is perhaps even more mysterious.

Posted by Mixner | June 18, 2008 2:27 AM

And lesbianism is perhaps even more mysterious.

I read about a study today in the Marin I-J (sadly, I can't find the article online) that looked at sexual arousal based on gender.

Basically, men could be aroused by naked pictures of their preferred gender. Women weren't aroused by naked pictures of either gender. (Duh.)

But women could be aroused by pictures/movies of sexualized contact, people touching, kissing, screwing, etc. And it didn't matter the genders involved: hetero, two women, even two men all aroused women equally.

(Method of measuring arousal was blood dilation, if you care. And yes, I know blood itself doesn't dilate, but this is from memory and I'm not a biologist.)

The author theorized that feminine sexuality was more mutable than male sexuality, and represented a middle ground between heterosexual and homosexual male sexuality.

FWIW.

Posted by scythia | June 18, 2008 3:00 AM

Couldn't agree with Dave more. Everyone has at least one kid that throws all your intentions/expectations out the window. Our was a girl born in a house with all boy toys and a tomboy mother who loves pink, princesses, dresses, and has 20 pairs of shoes (thanks to her grandparents, drives me crazy!).

It's genetic folks.

Posted by Robert P. | June 18, 2008 10:22 AM

Men- the choice of balanced brains.

Posted by Walt | June 18, 2008 12:38 PM

My female neuro-endocrinology professsor laughed at the idea of social construction of gender behavior. People may want to believe that gendered behavior is mostly constructed, but when common sense and serious science disagree with you, you're probably SOL.

Posted by Chris | June 18, 2008 12:51 PM

Steve this means having a gay identical twin means you have roughly 450% greater chance of being gay yourself, 22% v. ~4%.

Still, it is hard to say from this that homosexuality is genetic. If being genetically identical makes homosexuality more likely, but only up to 22% from 4%, it seems more likely that it is an environmental factor, and that the genes just affect how susceptible one is to it.

I mean, resistance to disease is genetic, but smallpox and polio are not considered "genetic" diseases.

I suppose you are trying to say that the real correlation between twins is more like 80-100%, it's just that so many are in the closet, so there must be a gay gene or combination of genes.

I think that the "early developmental environmental" explanation is much better, whether it is immune response or the result of an infection.

Posted by Glaivester | June 18, 2008 1:12 PM

For what it's worth, I'm conservative-liberatarian who thought the left was probably right on this issue from a long time back. Yeah, their evidence is looking better all the time. No big sweat; homosexual sex is fine so long as no one is forcing me to do it. :)

But something occurs to me.

Assume the Left is correct in spades. Assume, for a moment, that there is a large genetic componenet to human sexuality that makes homsosexual activity pleasurable/attractive.

How long before the technology to screen and either "correct" the gene(s) involved becomes possible? How many straight parents will NOT abort or alter the 3-5% of embryos involved?

The proportion of homosexuals in the next generation could end up being a LOT smaller. A large genetic component could, ironically, be a terrible threat the future existence of a homosexual minority (presumably some would arise anyway through unique environment factors, but only a minority of a minority).

Question: Would such selection by parents be wrong? Or any differrent from changing an unborn childs hair or eye colour? Or say, a tendency to play sports? When does a socially unusual condition become a disease, or a choice? Note, en passant, attempts to ban screening/selection on this basis are as likely to be as utterly futile as laws currently banning infant sex selection in India, especially as tech costs come down.

Posted by Alistair Morley | June 18, 2008 6:15 PM

For what it's worth, I'm conservative-liberatarian who thought the left was probably right on this issue from a long time back. Yeah, their evidence is looking better all the time. No big sweat; homosexual sex is fine so long as no one is forcing me to do it. :)

But something occurs to me.

Assume the Left is correct in spades. Assume, for a moment, that there is a large genetic componenet to human sexuality that makes homsosexual activity pleasurable/attractive.

How long before the technology to screen and either "correct" the gene(s) involved becomes possible? How many straight parents will NOT abort or alter the 3-5% of embryos involved?

The proportion of homosexuals in the next generation could end up being a LOT smaller. A large genetic component could, ironically, be a terrible threat the future existence of a homosexual minority (presumably some would arise anyway through unique environment factors, but only a minority of a minority).

Question: Would such selection by parents be wrong? Or any differrent from changing an unborn childs hair or eye colour? Or say, a tendency to play sports? When does a socially unusual condition become a disease, or a choice? Note, en passant, attempts to ban screening/selection on this basis are as likely to be as utterly futile as laws currently banning infant sex selection in India, especially as tech costs come down.

Posted by Alistair Morley | June 18, 2008 6:16 PM

To all of the proponents of the "biological gender differences" camp: then how DO you explain that not every little girl plays with dolls (and not all littel girls who don't like dolls are lesbians)? How DO you explain that some little boys aren't interested in playing sports (and may even grow up to be hetero)? I am truly asking.

It's fairly useless to say "Most do x, therefore they're born that way (except for the ones who don't)"--that is evidence of absolutely nothing, other than having circumstantial evidence which you are admitting is contridicted by other people's circumstantial evidence.

How do you explain the fact that pink was once considered a masculine color, and writing poetry was considered a masculine pursuit? How about explaining why pink is acceptable for boys in other cultures?

Cultural gender differences are so ingrained in people that little boys and little girls are often treated differently from birth--not that the parents even know they are doing it. And no one raises their kid in a vaccuum; kids pick up on things from books, tv, movies, strangers, everywhere. Little kids are information gathering fiends, and I doubt even Jodie Foster's kids are immune to our culture.

Perhaps, as someone mentioned before, the preference is genetic, but the classification is wrong. Then we have to accept a different model of categorizing actions and preferences other than the binary male and female because that binary simply doesn't work.

Posted by LR | June 18, 2008 6:19 PM

Well, LR, it's all to do with graduate-level multivariate statistics, logic, and hypothesis testing...

If your hypothesis of principally gender conditioning held, residual variance would dominate the system, and "knowing" the genetics or pre-natal data on an individual would give no information (in the technical sense) on adult sexuality. But neither are true, so we reject your hypothesis.

It doesn't mean H1 is true, but we can be pretty sure its not pure environment.

Sorry.

Posted by Alistair Morley | June 18, 2008 6:34 PM