# Does Anyone Believe Sexual Preference is 100% Genetic? **URL:** \ **Category:** Great Debates\ **Created:** [July 3, 2012, 2:26pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100 "2012-07-03T14:26:18Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 3, 2012, 3:54pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/21 "2012-07-03T15:54:47Z")
I’m not even sure if ‘congenital’ is exactly the right term - I mean sexuality appears to be nearly-immutable once established, but are we even sure it’s completely established at birth (as opposed to being still somewhat malleable (somehow) in early years. The argument is a red herring anyway. It doesn’t matter whether homosexuality is genetic, congenital, or especially immutable - or even if it is, as idiots are fond of claiming, a ‘lifestyle choice’. None of those factors are valid reasons for people to interfere with, oppress, or purposely disadvantage homosexuals who merely wish to go about their business. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [July 3, 2012, 3:55pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/22 "2012-07-03T15:55:59Z")
Can I be the 4th or 5th person to steer people away from using the word ‘genetic’ in this argument? It makes the whole thread sound dumb although you may not understand why if you don’t know much about sexual differentiation in mammals. We have this problem in every thread of this type. Sexual differentiation is caused directly by the _sex hormones_ like testosterone, estrogen and DHT. Genetics only play an indirect role in sexual differentiation and there are many ways that the process go wrong at multiple stages. The fact that you have the body type of a male or female (or some combination of those) isn’t because you have XX or XY (or XYY etc) chromosomes. It is because you were exposed to a certain set of sex hormones prenatally. Genetics is usually the trigger for cascade of events that lead to the appropriate sex hormone exposure but all of that goes out the window when we look at anomalies in prototypical or brain sexual differentiation. I went to graduate school in the behavioral neuroscience of sexual differentiation. The literal answer to the question is that genetics probably have very little to do with sexual preference but it is mostly biological and predetermined before birth especially in males. ---
**Author:** ![NojNoj](https://avatars.discourse-cdn.com/v4/letter/n/2bfe46/32.png) [@NojNoj](https://boards.straightdope.com/u/NojNoj)\ **Post date:** [July 3, 2012, 4:01pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/23 "2012-07-03T16:01:05Z")
> [@Shagnasty](#): > > The fact that you have the body type of a male or female (or some combination of those) isn’t because you have XX or XY (or XYY etc) chromosomes. It is because you were exposed to a certain set of sex hormones prenatally. That’s an antiquated idea that’s been soundly disproven. Genetics leads directly to differences in brain structure between genders. Also, overall body type (while secondary sex characteristics may act in accordance with what you say about hormonal control.) Besides being wrong, this theory also led to the famous tragedy of David Reimer ([David Reimer - Wikipedia](http://en.wikipedia.org/wiki/David_Reimer)) To me, it is an example of a political agenda trumping sound science. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [July 3, 2012, 4:04pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/24 "2012-07-03T16:04:26Z")
> [@NojNoj](#): > > That’s an antiquated idea that’s been soundly disproven. Genetics leads directly to differences in brain structure between genders. Also, overall body type (while secondary sex characteristics may act in accordance with what you say about hormonal control.) > > Besides being wrong, this theory also led to the famous tragedy of David Reimer ([David Reimer - Wikipedia](http://en.wikipedia.org/wiki/David_Reimer)) > > To me, it is an example of a political agenda trumping sound science. Well there goes all of my PhD work out the window then. Looks like I got hooked up with some a group of Ivy League charlatans posing as experts in the field of sexual differentiation. Please straighten us all out then in detail please. Start with the basics because I doubt anyone here knows as much as you do. Hint: Your example shows you didn’t understand a single word I wrote. It is a correct example but demonstrates MY point. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [July 3, 2012, 4:04pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/25 "2012-07-03T16:04:38Z")
> [@NojNoj](#): > > To me, it is an example of a political agenda trumping sound science. I think you’re on the verge of hijacking your own thread. Are you not actually interested in the issue you were originally discussing (genes and sexual preference)? ---
**Author:** ![Minnie\_Luna](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@Minnie\_Luna](https://boards.straightdope.com/u/Minnie_Luna)\ **Post date:** [July 3, 2012, 4:05pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/26 "2012-07-03T16:05:56Z")
> [@Marley23](#): > > People who study the subject see it differently. 😉 I understand this the same way **Ruken** does: the leading theory is that as a woman carries more sons to term, the prenatal hormone environment changes. The result is that the more sons a woman has, the greater the chance the younger sons will be gay. I think the odds increase something like 33 percent each time, which means the chances are fairly low even after several births. There are a lot of studies about birth order and homosexuality. A number of these studies also look at handedness. [Biodemographic and physical correlates of sexual orientation in men. Archives of Sexual Behavior [0004-0002] Schwartz, Gene yr:2010 vol:39 iss:1 pg:93 -109](http://www.springerlink.com/content/m232wur016t3nu37/) > [@](#): > > To better understand sexual orientation from an evolutionary perspective, we investigated whether, compared to heterosexual men, the fewer direct descendants of homosexual men could be counterbalanced by a larger number of other close biological relatives. We also investigated the extent to which three patterns generally studied separately––handedness, number of biological older brothers, and hair-whorl rotation pattern––correlated with each other, and for evidence of replication of previous findings on how each pattern related to sexual orientation. We surveyed at Gay Pride and general community festivals, analyzing data for 894 heterosexual men and 694 homosexual men, both groups predominantly (~80%) white/non-Hispanic. The Kinsey distribution of sexual orientation for men recruited from the general community festivals approximated previous population-based surveys. Compared to heterosexual men, homosexual men had both more relatives, especially paternal relatives, and more homosexual male relatives. We found that the familiality for male sexual orientation decreased with relatedness, i.e., when moving from first-degree to second-degree relatives. We also replicated the fraternal birth order effect. However, we found no significant correlations among handedness, hair whorl rotation pattern, and sexual orientation, and, contrary to some previous research, no evidence that male sexual orientation is transmitted predominantly through the maternal line. The 33% number you quoted is correct, from a 1996 study. [Homosexuality in Men and Number of Older Brothers](http://www.ncbi.nlm.nih.gov/pubmed/8540587) > [@](#): > > OBJECTIVE: > > This study investigated whether homosexual men have a higher mean birth order than heterosexual men primarily because they have more older brothers or because they have more older siblings of both sexes. > METHOD: > > For the main analyses, 302 heterosexual men were individually matched on year of birth with an equal number of heterosexual men. Each completed a self-administered, anonymous questionnaire concerning family background and other biodemographic information. > RESULTS: > > Logistic regression analysis showed that homosexuality was positively correlated with the proband’s number of older brothers but not with older sisters, younger brothers, younger sisters, or parental age at the time of the proband’s birth. Each additional older brother increased the odds of homosexuality by 33%. > CONCLUSIONS: > > These results restrict the range of possible theories of the birth order phenomenon to those that can explain not only why older brothers increase the probability of homosexuality in later-born males but also why older sisters neither enhance this effect nor counteract it. [This paper may explain the why.](http://www.ncbi.nlm.nih.gov/pubmed/9156085) > [@](#): > > In men, sexual orientation correlates with the number of older brothers, each additional older brother increasing the odds of homosexuality by approximately 33%. It is hypothesized that this fraternal birth order effect reflects the progressive immunization of some mothers to Y-linked minor histocompatibility antigens (H-Y antigen) by each succeeding male fetus, and the concomitantly increasing effects of H-Y antibodies on the sexual differentiation of the brain in each succeeding male fetus. This hypothesis is consistent with a variety of evidence, including the apparent irrelevance of older sisters to the sexual orientation of later-born males, the probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring. Evolutionarily, this could easily be explained by the first and older males wanting to ensure their genes are passed along so they try and make sure that any younger male siblings are less reproductively capable. ---
**Author:** ![Simplicio](https://avatars.discourse-cdn.com/v4/letter/s/c37758/32.png) [@Simplicio](https://boards.straightdope.com/u/Simplicio)\ **Post date:** [July 3, 2012, 4:09pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/27 "2012-07-03T16:09:58Z")
> [@NojNoj](#): > > That’s an antiquated idea that’s been soundly disproven. Genetics leads directly to differences in brain structure between genders. Also, overall body type (while secondary sex characteristics may act in accordance with what you say about hormonal control.) Cite. > [@](#): > > Besides being wrong, this theory also led to the famous tragedy of David Reimer ([David Reimer - Wikipedia](http://en.wikipedia.org/wiki/David_Reimer)) That wikiarticle says the opposite of what you claim > [@article](#): > > It supported the arguments of those who feel that prenatal and early-infantile hormones have a strong influence on brain differentiation, gender identity and perhaps other sex-dimorphic behavior. > [@](#): > > To me, it is an example of a political agenda trumping sound science. What a surprise :rolleyes: ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [July 3, 2012, 4:16pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/28 "2012-07-03T16:16:45Z")
> [@Minnie\_Luna](#): > > Evolutionarily, this could easily be explained by the first and older males wanting to ensure their genes are passed along so they try and make sure that any younger male siblings are less reproductively capable. Or by the mother trying to ensure that one or more of the younger males will be unentangled with a woman and free to support & protect her and her daughter(s). ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 3, 2012, 4:29pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/29 "2012-07-03T16:29:04Z")
> [@NojNoj](#): > > To me, it is an example of a political agenda trumping sound science. So what? Politics and science aren’t the same thing, or trying to achieve the same goals as one another. ---
**Author:** ![yorick73](https://avatars.discourse-cdn.com/v4/letter/y/b5a626/32.png) [@yorick73](https://boards.straightdope.com/u/yorick73)\ **Post date:** [July 3, 2012, 4:47pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/30 "2012-07-03T16:47:05Z")
> [@Minnie\_Luna](#): > > Evolutionarily, this could easily be explained by the first and older males wanting to ensure their genes are passed along so they try and make sure that any younger male siblings are less reproductively capable. > [@Der\_Trihs](#): > > Or by the mother trying to ensure that one or more of the younger males will be unentangled with a woman and free to support & protect her and her daughter(s). Even if true I don’t see why we need to have some kind of evolutionary “explanation” for the phenomena. It may just be the way it works out regardless of whether it provides some sort of benefit for anyone involved. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [July 3, 2012, 4:53pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/31 "2012-07-03T16:53:35Z")
> [@yorick73](#): > > Even if true I don’t see why we need to have some kind of evolutionary “explanation” for the phenomena. It may just be the way it works out regardless of whether it provides some sort of benefit for anyone involved. If a trait lasts a long time and is seen in a wide variety of species, it’s likely that it is associated with some type of benefit or other. I’ve never heard the idea that **Minnie Luna** proposes - in fact I’m not sure it even makes any sense because it makes it sound like the male fetuses are involved in selecting traits for younger siblings and I have trouble believing that - but I have often seen the theory that a homosexual tribe member could improve the group’s chances of survival by helping raise children and not competing for mates, for example. ---
**Author:** ![grude](https://avatars.discourse-cdn.com/v4/letter/g/e47774/32.png) [@grude](https://boards.straightdope.com/u/grude)\ **Post date:** [July 3, 2012, 4:59pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/32 "2012-07-03T16:59:52Z")
The “100% genetic” meme started as a defense mechanism by the gay community against the conversion therapy places and “gay is a choice” propaganda which I guess was being bought by some members of the public? Before the conversion therapies and “gay is a choice” thing came into wide discussion no one was pushing “100% genetic”. If you want to blame someone blame the people pushing conversion therapy and trying to paint gays as sinners. ---
**Author:** ![grude](https://avatars.discourse-cdn.com/v4/letter/g/e47774/32.png) [@grude](https://boards.straightdope.com/u/grude)\ **Post date:** [July 3, 2012, 5:01pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/33 "2012-07-03T17:01:59Z")
> [@Marley23](#): > > I’ve never heard the idea that **Minnie Luna** proposes - in fact I’m not sure it even makes any sense because it makes it sound like the male fetuses are involved in selecting traits for younger siblings and I have trouble believing that . There is no intention involved, rather the theory holds that it is a “side effect” of multiple pregnancies. That previous pregnancies with male fetuses change the womb. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [July 3, 2012, 5:07pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/34 "2012-07-03T17:07:08Z")
> [@grude](#): > > The “100% genetic” meme started as a defense mechanism by the gay community Do you have a cite for that? ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [July 3, 2012, 5:08pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/35 "2012-07-03T17:08:33Z")
> [@grude](#): > > The “100% genetic” meme started as a defense mechanism by the gay community against the conversion therapy places and “gay is a choice” propaganda which I guess was being bought by some members of the public? Before the conversion therapies and “gay is a choice” thing came into wide discussion no one was pushing “100% genetic”. > > If you want to blame someone blame the people pushing conversion therapy and trying to paint gays as sinners. Also, I’ve heard people say they don’t want to bring up the possibility of non-genetic in-the-womb influences because they fear it’ll be twisted into blaming the mother. ---
**Author:** ![grude](https://avatars.discourse-cdn.com/v4/letter/g/e47774/32.png) [@grude](https://boards.straightdope.com/u/grude)\ **Post date:** [July 3, 2012, 5:13pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/36 "2012-07-03T17:13:26Z")
> [@Marley23](#): > > Do you have a cite for that? In a single link? Nope but others who have the time could deluge you with examples of the public controversy from the last few years. Look at this for example: [http://thinkprogress.org/lgbt/2011/09/16/320808/boehner-claims-homosexuality-is-a-choice-in-effort-to-preserve-defense-of-marriage-act/](http://thinkprogress.org/lgbt/2011/09/16/320808/boehner-claims-homosexuality-is-a-choice-in-effort-to-preserve-defense-of-marriage-act/) [http://www.alternet.org/sex/153877/is\_gay\_a\_choice\_the\_science\_behind\_actress\_cynthia\_nixon's\_controversial\_remarks](http://www.alternet.org/sex/153877/is_gay_a_choice_the_science_behind_actress_cynthia_nixon%27s_controversial_remarks) > [@](#): > > Activists have long combated attacks on LGBT identities by highlighting the science showing that homosexuality is genetic ---
**Author:** ![NojNoj](https://avatars.discourse-cdn.com/v4/letter/n/2bfe46/32.png) [@NojNoj](https://boards.straightdope.com/u/NojNoj)\ **Post date:** [July 3, 2012, 5:14pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/37 "2012-07-03T17:14:40Z")
> [@Der\_Trihs](#): > > Also, I’ve heard people say they don’t want to bring up the possibility of non-genetic in-the-womb influences because they fear it’ll be twisted into blaming the mother. Problem with that line of thought is the same people end up attacking innocents, like Cynthia Nixon: [http://www.cbsnews.com/8301-207\_162-57367836/actress-gay-by-choice-claim-riles-activists/](http://www.cbsnews.com/8301-207_162-57367836/actress-gay-by-choice-claim-riles-activists/) simply for saying something about her personal life that doesn’t happen to agree with the talking-point of the day. ---
**Author:** ![heathen\_earthling](https://avatars.discourse-cdn.com/v4/letter/h/13edae/32.png) [@heathen\_earthling](https://boards.straightdope.com/u/heathen_earthling)\ **Post date:** [July 3, 2012, 5:15pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/38 "2012-07-03T17:15:15Z")
> [@Sofis](#): > > think part of the reason for this is that congenital is a “bad” word, in that it is frequently followed by such things as “disease”, “disorder” or “heart defect”. And it contains the naughty word “genital”! ---
**Author:** ![Inner\_Stickler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inner_stickler/32/318_2.png) [@Inner\_Stickler](https://boards.straightdope.com/u/Inner_Stickler)\ **Post date:** [July 3, 2012, 5:17pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/39 "2012-07-03T17:17:15Z")
We talked abut that when it happened. I don’t see why Nixon forgetting the word bisexual is relevant. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [July 3, 2012, 5:20pm UTC](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100/40 "2012-07-03T17:20:44Z")
> [@grude](#): > > In a single link? Nope but others who have the time could deluge you with examples of the public controversy from the last few years. I’m aware of the controversy. I’m asking if you can cite the idea that the gay community _came up with_ the idea that homosexuality is genetic. I think the main reason people boil the issue down to ‘it’s genetic’ is a poor understanding of science. > [@NojNoj](#): > > Problem with that line of thought is the same people end up attacking innocents, like Cynthia Nixon So, about the genetic thing? There’s nothing about that in the article. [Previous page](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100.md?page=1) [Next page](https://boards.straightdope.com/t/does-anyone-believe-sexual-preference-is-100-genetic/627100.md?page=3)