Biological evidence for homosexuality?
August 17, 2010 5:36 PM   Subscribe

hey... I was wondering where I can find the best evidence to prove that sexuality is biological or womb hormonally rather than child rearing caused? Just for my parents who are damn annoying. Thanks!
posted by antgly to Human Relations (29 answers total) 5 users marked this as a favorite
My impression is that researchers are still struggling to understand the causes of sexual orientation. A glance at the wikipedia page about it shows a list of competing hypotheses, experiments, etc. From this, my personal conclusion is that laypeople are not yet in a position to hold valid beliefs about the causes of, for instance, homosexuality.
posted by polymodus at 5:50 PM on August 17, 2010 [2 favorites]

Here's a related question from 2005.

I'll repeat my answer from that thread:
This might not answer the literal question you've asked, but I hope it helps.

I like Jonah Goldberg's solution:

(1) We just don't know how much of homosexuality is a choice vs. environmental vs. congenital. (Maybe it's all of those things.)

(2) But even if it's actually a choice or environmental, we still don't really know anything about how people become gay.

(3) So, for practical purposes, people are essentially born gay.

From this, he concludes: "it doesn't matter how some so-called 'waverers' became gay. Because they are that way now. And unless conservatives are going to endorse some pretty draconian and, more to the point, unenforceable policies, gays aren't going to go away or be 'cured.'"
I'll also repeat a comment of mine from a different thread (which I won't bother linking because the thread as a whole isn't relevant):
It's a debate that supporters of gay rights mistakenly believe will clinch their position. They're not thinking about things from the other side's perspective. If you really believe homosexuality is just plain bad, it doesn't matter if it's a choice or inborn. Compare: even if research shows that pedophilia or alcoholism are inborn, does that make them socially acceptable? No. The reason gays should be accepted isn't that they have no choice (which would call into question how to deal with bisexuals!). Gays should be accepted because there's nothing wrong with homosexuality -- no matter why people are gay.
I hope this is helpful on some level. I'm sure people will link to relevant research, but I would caution you that the scientific question may be a red herring as far as your discussion with your parents.
posted by Jaltcoh at 5:51 PM on August 17, 2010 [11 favorites]

There is no *conclusive* evidence one way or another (Wikipedia's Biology and sexual orientation page is a good place to start exploring). There is, however, plenty of evidence of homosexual/bisexual behavior among many, many animal species,* and there are some twin studies that are highly *suggestive* of a genetic component, though, with a twin raised in a different family from its gay sibling has a higher than expected likelihood of homosexuality as well. Bottom line is simple: given the incredible complexities of human psychosexual development and desire, there are probably multiple paths to homosexuality that manifest differently in different people - i.e., someone with a small genetic predisposition might not feel much strong homosexual desire during most or all of their life, while someone with no genetic predisposition could possibly, through environmental/childhood/adulthood experiences, become an adult who enjoys same-sex erotic encounters.

Homosexuality, like most complex psychological/biological traits, is almost certainly caused by a mix of biological and environmental factors. It's just a fact.

I think I know what you're trying to do; when I came out to my dad, one of his first questions was "Is it something I did?" This is a common reaction that can be helped by pointing them toward awesome resources for parents like But honestly, no one is completely certain how much of homosexuality is caused by genetics.

*I cannot recommend Bagemihl's book strongly enough on this point; the 2nd half is nothing but page after page of detailed examples from the animal kingdom
posted by mediareport at 5:57 PM on August 17, 2010 [1 favorite]

What they all said, plus this from Randall Munroe of XKCD:

"You don't use science to show that you're right, you use science to become right."
posted by richyoung at 8:50 PM on August 17, 2010

Response by poster: Pretty much, my Dad also tells me "you can change if you really want to"... Pathetic... Biological proof can help me in this, because at least I need something more than personal experience on my side.
posted by antgly at 8:53 PM on August 17, 2010

Question for dad: could he permanently change his own sexuality if he really wanted to?
posted by hermitosis at 9:21 PM on August 17, 2010 [8 favorites]

Ask your Dad if he can change if he really wants to. Ask him to explain why not.
posted by amanda at 9:23 PM on August 17, 2010

posted by amanda at 9:24 PM on August 17, 2010

Response by poster: He says that maybe he can if he really wanted to.
posted by antgly at 9:28 PM on August 17, 2010

Almost all complex psychological phenomena, like mediareport alluded to above, are mostly due to an interaction of genes and environment. While genes might predispose you towards a range of behaviors, those behaviors will depend on your environment. To further complicate things, your genes don't stay the same throughout your life! They turn off and on (or are expressed) on the order of minutes. This expression often depends on environmental factors. Another important thing to remember is that genes don’t cause complex behavior: they predispose an individual towards a range of behaviors. The behaviors engaged in out of this range of potential behaviors impact later circumstances and further refine the expression of a person’s genes, which has the effect of limiting behavior choices.

Perhaps one could have a genetic makeup that predisposes him towards being gay which, in concert with certain environmental conditions, could mean that the person finds themselves attracted to people of the same sex. In other environmental conditions, or in cases of epistasis (i.e., gene-gene interaction), this would not result in the person being attracted to people of the opposite sex. Importantly, no single vulnerable allele is risk-inducing under all contexts.

Remember also that there are a huge number of factors that fall into the environmental category beyond parenting alone. In vitro hormones, stress/trauma, chemicals, your experience in school, your interactions with your friends...these ALL play a role. They all work with each other and with your genes (and neurochemistry/structure) to determine your behavior.

All that said, there is plenty of evidence that factors outside of explicit choices lead someone to be gay. For example, the more older brothers you have, the more likely you are to be gay(pdf). In studies of female rats and their offspring described to me by Marc Breedlove(eponysterical), each older brother that a rat had doubled the likelihood that a given rat would display homosexual behavior. This effect held even when female rats were impregnated with male fetuses that were then aborted, which indicates that it's not necessarily something about the interactions with their brothers that led them to be rat gay. One hypothesis to explain this is that women have a immune system response to carrying male fetuses which may be a factor that goes in that whole gene by environment interaction pile.

As another example(pdf) (this one goes out to the ladies), the ratio of the length of the ring finger to the index finger is close to 1 in women, less than 1 in men, lesbian women, and gay men. This suggests that there is something biologically different about lesbian women, although it is just as likely that some child development factors that contributed to them being lesbians also affected their finger length.

All that said, here's some food for thought. I believe that most people attach a number of qualities to things that are considered to be heritable. Namely, it seems to me that the general public believes that, if there is not a single gene responsible for a given phenomenon, and if it can be demonstrated that that phenomenon is not entirely heritable, then there is something that either we as a culture or we as individuals can do about that phenomena. Additionally, in some cases, when a trait is seen as not totally heritable, it becomes value-laden to the general public. In contrast, if the trait was demonstrated to be completely heritable it could be considered to be value neutral. This raises three specific issues for debate: Given the evidence that there is most likely not a single isolatable gene for any complex psychological/behavioral phenomena, and none of these phenomena are 100% heritable, what (and whose) needs do such perspectives serve?
posted by emilyd22222 at 9:30 PM on August 17, 2010 [1 favorite]

Just saw this article in the LA Times on Sunday, about possibly reducing the likelihood of homosexuality, beginning the womb. Seems to be more related to female sexual orientation rather than male though.
posted by vignettist at 10:06 PM on August 17, 2010

Just so you know, however your approach: there is no scientific argument that faith, bias, prejudice, privilege, or ignorance can't willfully refuse to honor. I'm very glad you are discussing this with your parents, and there are lots of resources out there to help them. But don't expect to win this fight with logic, at least not in the short term. It takes time for it to sink in, time for them to come to terms with their own doubts and concerns, time for you demonstrate consistently that you are you and not likely to change anytime soon.

My mom wasn't religious or anything, and it took her years. It simply wasn't how she imagined me, and she'd had about 20 years of imagination built up for me to combat. It was a hard fight because I didn't want her to lose that version of me she'd imagined -- i just wanted to reconcile it with the facts. In the end I'm not sure that was possible, but today she is very supportive and accepting and even made her first gay friend, reaching out to (I can't believe I'm saying this) her hairdresser and helping him adjust to their small-town environment.

It took years from the time my dad first snooped in my email when I was 18 to get to the point where I could actually discuss my life openly with him, or to the point where he would casually mention my partner to other people without even wondering what they would think.

So, choose your battles carefully for now, and I recommend choosing the ones which are all about you -- your life as it pertains to yourself, not to them. They will run around behind you playing catch-up, fretting and threatening and stonewalling, until one day something will crack and they'll just give up and love you.

Or else they won't. And if you want to play hardball, that's what this comes down to. "Do you really love me and want me to continue sharing my life with you -- even if I turn out to always be this way? Regardless of whether you think it's a choice?" Don't ask any questions you are not prepared to hear the answer to. And even if it doesn't work out and it all seems to fall apart, remember: time. A lot can change in a year or five. You are nothing if not evidence of that!
posted by hermitosis at 10:35 PM on August 17, 2010 [15 favorites]

A recent article titled 'Late-Life Lesbians' Reveal Fluidity Of Sexuality might be relevant to this discussion – it talks about how sexuality may not be as static as previously thought.
posted by halogen at 12:08 AM on August 18, 2010 [1 favorite]

> choose your battles carefully for now, and I recommend choosing the ones which are all about you -- your life as it pertains to yourself, not to them. They will run around behind you playing catch-up, fretting and threatening and stonewalling
This. OP, despite the positive aspect of being able to talk with your parents, they are essentially psychologically hurtful for the time being. While they adjust, be careful to not waste your youthful energy on a problem that is not yours (it's their problem to learn to deal with it). Instead, spend time with friends, succeed with your education, etc, etc.
posted by knz at 1:22 AM on August 18, 2010 [1 favorite]

Ask what he thinks about homosexuality found among a small percentage animals. That's about as natural as it gets, unless he thinks animals are capable of "choosing" a "lifestyle".
posted by windbox at 5:42 AM on August 18, 2010

There are many very informative and intelligent answers above. I want to suggest some other possible replies to the assertion "you can change if you really want to". It's very doubtful that you could change even if you really wanted to, but you could certainly pretend to do so (which is to day, go back into the closet). But you don't want to. Your father could then argue that you should want to, because homosexuality is unnatural, immoral, or contrary to God's will. All of these accusations are, of course, entirely false. It is just as natural for homosexuals to be homosexual as it is for heterosexuals to be heterosexual. I would add that very few people would be so perverse as to practice a form of sexuality that is not natural for them. Homosexuality in itself does not harm anyone (it can be practised in a harmful way, but it is no more susceptible to such abuse than heterosexuality is) and therefore it is perfectly moral. And as for God's will, we still have no clear evidence that such a being even exists, much less do we have definite knowledge of His will. There are a thousand different religions each with their own concept of God's will, some of which are even gay-positive. If necessary you can belong to Wicca and worship the Goddess, who has no objection to homosexuality (and who is at least as believable as Yahweh the Omnipotent, so beloved of bigots everywhere).

Another detail. I was once asked, if it is true that homosexuality is as natural for homosexuals as heterosexuality is for heterosexuals, is pedophilia natural for pedophiles? This is part of a general argument which is often made, that if society tolerates deviant forms of sexuality, the floodgates open up to every form of sexual perversion, such as pedophilia, bestiality, necrophilia, etc. Or in other words, it's the old familiar slippery slope argument. This, too, is a fallacious argument. Even though every form of sexuality, including pedophilia, appears to be natural to those who have that inclination or orientation, that is only half of the picture. When two homosexuals have sex, it is natural for both of them. When a pedophile inflicts his lust upon a child, it will seem natural to him but it will not be natural for that child. In this case, principles of morality do apply. Sex should not be harmful to any of the participants.

The issue of polygamy is also often raised and it is more complicated. In practice, polygamy usually involves some degree of abuse of the women who effectively form a harem for some sexually greedy male. However, if polygamy is done as a marriage with true informed consent by all parties concerned, in theory it is acceptable. Society has to be cautious about that.
posted by grizzled at 5:52 AM on August 18, 2010 [1 favorite]

Quoting myself, from a very similar question last December:


Firstly, it's worth pointing out that the whole "nature vs. nurture" debate is almost always a false dichotomy. Everywhere I've heard of people searching for genetic causes to phsychological phenomena has turned up with the answer "actually, it's a bit of both". Think of it like height: your parents' genetic information plays a big role in your height, and so does your diet, excercise, exposure to disease, etc. It's very rare for things to be purely nature or purely nurture.

I'm not an expert on this stuff, but it's something I've done a bit of reading around.

Finger length ratios are correlated with birth order, levels of sex hormones you were exposed to in the womb and your eventual sexual orientation. So it looks pretty certain that something that happens in the womb influences a person's sexuality. [Nature paper, free version, BBC News writeup]

As regards the birth order, it's not just the case that being raised with lots of older brothers makes a man gay. Being born to a mother who has already given birth to boys increases a boy's odds even if he's not raised with that family, so it really does seem to be a pre-natal event rather than post-natal (nature, not nurture). [PNAS paper]

About 8% of male sheep exhibit homosexual tendencies, suggesting that if homosexuality is purely cultural then sheep have a lot more culture than we previously thought. Further, brain scans and dissection show different brain structures in homosexual sheep as compared to heterosexual sheep, in areas of the brain thought to be formed very early in development (probably before birth, maybe in infancy). [Endocrinology paper, Endocrinology Editorial (more readable, better background), Medical News writeup, New Scientist]

Also noted in that Endocrinology paper is that stright men's "interstitial nucleus of the anterior hypothalamus (INAH3)" is bigger than straight women's, but that gay men's INAH3s are indistinguishable from women's, showing that this part of brain anatomy is strongly linked with orientation. (Big = attracted to women, small = attracted to men?) Science paper, New Scientist] Again, this brain development usually finishes before birth, strongly suggesting that this isn't due to a choice or a learned response.

There's a nice twin study in this Biological Psychology paper, which suggests that genetic factors account for a proportion of "potential for homosexual response" (in which they asked about hypothetical responses to various scenarios rather than actual sexual activity) - 37% in men, 46% in women. So genetics seems to play a big role, then womb conditions can be added to that, then environmental conditions on top of that.

So it might be (and probably is) the case that environmental conditions play a role in determining sexuality. But a person's genes, prenatal conditions (birth order, exposure to hormones) and pre-natal or infant brain development all play important roles in determining sexuality.

As a final note, even if you want to ignore this evidence and believe that homoseuality is not physiological on origin, can I suggest a change in your terminology? Calling it a "choice" would still only be true in the same sense that people "choose" to become depressed, or to have a New York accent, or to be phobic of something. You'd be talking about the way that someone's personality has developed in a given environment (generally shorthanded as referring to "nurture"). Talking about it as a "choice" implies to a lot of people that they just woke up one morning and thought "hey, from now on I'd be attracted to dudes!". As well as strawmanning your own argument, it also carries the implication that they're just doing it to be obstinate, for attention or whatever, and could snap out of it if they "chose", which is very insulting. I'm sure this isn't what you mean, but please bear in mind that it's what many people will think you mean which, in a conversation, is more important.
posted by metaBugs at 6:28 AM on August 18, 2010 [2 favorites]

It's not biological proof you need, it's tolerance from your parents.

Until the mid-60s homosexuality was illegal in Great Britain; considered a crime which carried a prison sentence. Many men tried to 'change' themselves and enter into marriage....many more visited glory-holes, kept their relationships secret, or were convicted by authorities. This still is the case in many other countries - Jamaica, for example, where gay men have sought asylum elsewhere; in Senegal, gay men who have died from AIDS are being dug up and dumped on their parents' doorsteps. Yet people, apparently, still 'choose' to be gay in the eyes of those who believe that sexuality is purely a choice. This is not how it works and people are being abused, assaulted, imprisoned and killed because of a part of themselves that is themselves, not a personal choice.
posted by mippy at 6:28 AM on August 18, 2010

I think when many social conservatives say that gay people could choose to be straight, they really mean "Get back in the closet and shut your perverted mouth. Why aren't you ashamed of yourself like any decent fairy was in my day? Is it really so hard for you to just pretend to like girls, get married, and hide? It worked for me and my uncles."

So, the important thing to remember is, some day people like that will be dead.
posted by General Tonic at 6:51 AM on August 18, 2010 [4 favorites]

Why the hell would anyone choose to be gay? What is your father's rationale for believing that someone would choose a sexual orientation that is so widely persecuted and reviled?
posted by Anonymous at 7:58 AM on August 18, 2010

You might want to steer your father towards research that is critical of "ex-gay" therapies.
There is now a large body of research evidence that indicates that being gay, lesbian or bisexual is compatible with normal mental health and social adjustment.[1] Because of this, the major mental health professional organizations do not encourage individuals to try to change their sexual orientation from homosexual to heterosexual. Indeed, such interventions are ethically suspect because they can be harmful to the psychological well-being of those who attempt them; clinical observations and self-reports indicate that many individuals who unsuccessfully attempt to change their sexual orientation experience considerable psychological distress. For these reasons, no major mental health professional organization has sanctioned efforts to change sexual orientation and virtually all of them have adopted policy statements cautioning the profession and the public about treatments that purport to change sexual orientation.[2][3][4]
posted by muddgirl at 8:12 AM on August 18, 2010

Here's more on Wikipedia about conversion therapy. "The American Psychological Association appointed the Task Force on Appropriate Therapeutic Responses to Sexual Orientation to review the available research. The Task Force reached in the following findings:
...There are no studies of adequate scientific rigor to conclude whether or not recent SOCE do or do not work to change a person’s sexual orientation. Scientifically rigorous older work in this area (e.g., Birk, Huddleston, Miller, & Cohler, 1971; James, 1978; McConaghy, 1969, 1976; McConaghy, Proctor, & Barr, 1972; Tanner, 1974, 1975) found that sexual orientation (i.e., erotic attractions and sexual arousal oriented to one sex or the other, or both) was unlikely to change due to efforts designed for this purpose. Some individuals appeared to learn how to ignore or limit their attractions. However, this was much less likely to be true for people whose sexual attractions were initially limited to people of the same sex.

Although sound data on the safety of SOCE are extremely limited, some individuals reported being harmed by SOCE. Distress and depression were exacerbated. Belief in the hope of sexual orientation change followed by the failure of the treatment was identified as a significant cause of distress and negative self-image (Beckstead & Morrow, 2004; Shidlo & Schroeder, 2002).

Although there is insufficient evidence to support the use of psychological interventions to change sexual orientation, some individuals modified their sexual orientation identity (i.e., group membership and affiliation), behavior, and values (Nicolosi, Byrd, & Potts, 2000). They did so in a variety of ways and with varied and unpredictable outcomes, some of which were temporary (Beckstead & Morrow, 2004; Shidlo & Schroeder, 2002). Based on the available data, additional claims about the meaning of those outcomes are scientifically unsupported.
posted by muddgirl at 8:17 AM on August 18, 2010

Why the hell would anyone choose to be gay? What is your father's rationale for believing that someone would choose a sexual orientation that is so widely persecuted and reviled?

Why? Rebellion, sympathy, masochism, fitting into an outcast group might be more comfortable than the alternative . . .

This argument that nobody would choose such a terrible life (being gay) always struck me as counterproductive, and lacking logical rigor. Plenty of people "choose" to engage in behaviors and take on identities that aren't exactly easy and widely admired.
posted by General Tonic at 10:20 AM on August 18, 2010 [1 favorite]

Another related AskMe: Research supporting that homosexuals are born homosexuals. It's chock full of info!

I recommend watching the 2008 BBC documentary The Making of Me. In it actor John Barrowman "sets out to unearth what the latest scientific research can tell him about the origins of his homosexuality." He travels to different science centers in Europe and the U.S and meeting with the scientists who are focused on this question. It's compelling what the studies show. -- YouTube - 1 | 2 | 3 | 4 | 5 | 6.

Also watch CBS NEWS | 60 Minutes: The Science Of Sexual Orientation
"There are few issues as hotly contested — and as poorly understood — as the question of what makes a person gay or straight. It's not only a political, social, and religious question but also a scientific question, one that might someday have an actual, provable answer.

The handful of scientists who work in this under-funded and politically charged field will tell you: That answer is a long way off. But as Lesley Stahl reports, their efforts are already yielding tantalizing clues. One focus of their research is twins." [video]
There's also PBS | Frontline: 'A Gay Gene?' The documentary looks at various studies, such as those conducted by neuroscientist Simon Levay who has been doing research on brain structures and sexual orientation for quite some time. Dr. Levay's website.

Articles of interest:
Gay twin brothers may hold genetic clues. [Previous AskMe on the topic

Homosexuality and Biology.

A single gene answers question of sex.

The big brother effect.

Homosexuality linked to genes.

A genetic theory of homosexuality.

Darwinian Paradox of Male Homosexuality [PDF]. Previous FPP on the topic.
Also, take a look at the animal kingdom at large:
The Fabulous Kingdom of Gay Animals.

The Gay Animal Kingdom.

Gay Animals: Alternate Lifestyles in the Wild.

Gay Animals Out of the Closet.
A first-ever museum display, ‘Against Nature?’ opened in October 2006 at the University of Oslo's Natural History Museum in Norway, presenting 51 species of animals exhibiting homosexuality.
posted by ericb at 10:31 AM on August 18, 2010 [4 favorites]

Just for my parents who are damn annoying.

BTW -- a resource for your parents, if they're interested at some point:
PFLAG NYC (Parents, Families and Friends of Lesbians and Gays)
Chapter 380
Van Duzer St. Staten Island, NY 10304-2733.

Phone: (718) 907-6163.
posted by ericb at 10:36 AM on August 18, 2010

For those who don't use the embedded AskMe video here are direct YouTube links for 'The Making of Me' -- 1 | 2 | 3 | 4 | 5 | 6.
posted by ericb at 10:59 AM on August 18, 2010

This argument that nobody would choose such a terrible life (being gay) always struck me as counterproductive, and lacking logical rigor. Plenty of people "choose" to engage in behaviors and take on identities that aren't exactly easy and widely admired.

You know, this is one thing if you're living in a country where homosexuality is at least tolerated in some sections, and glamorized depending on what facet of popular culture you're looking at. But once you exit that quasi-tolerant bubble, and enter, say, Senegal, or Uganda, or Nigeria, or many parts of the Middle East, or any other number of countries, the benefits of "choosing" to be homosexual quickly drop off. I mean, shit, if you're living somewhere where it's punishable by death then it becomes quite a bit more difficult to argue about the benefits of counterculture membership.
posted by Anonymous at 11:22 AM on August 18, 2010

schroedinger, the point is that "omigod why on earth would anybody choose to be gay!" is a kneejerk cliche that's not a positive way of framing the debate, in *any* culture.
posted by mediareport at 4:25 PM on August 18, 2010

I totally understand where you're coming from, but you're asking the wrong question.

One doesn't stake out a position first, and then go looking for evidence to support that position.

Rather, one evaluates the total available evidence, and then determines what conclusion it points to.

And as others have pointed out, we simply don't have conclusive evidence on this question yet.

But I think you're asking the wrong question for another reason, as well. Because, as far as how we treat other people is concerned, what does it matter whether homosexuality is a matter of biology or choice? Even if every gay person has made a 100% deliberate choice to be that way, does that justify treating them as less than fully human? Does it somehow make a person's preferences in the bedroom any more another person's business than they were in the first place? Where is the evidence that homosexuality (regardless of where it comes from) is a bad thing?

But, yes, I'd suggest making this argument.

And it's also notable that homosexual behavior, of various kinds, has been observed in dozens of animal species.

Also, tell your dad I said he's kind of an asshole, and a soon-to-be-extinct dinosaur to boot. That should convince him.
posted by s0ckpupp3t at 7:33 PM on August 19, 2010 [1 favorite]

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