# Genealogy & Sexual Preference **URL:** \ **Category:** Factual Questions\ **Created:** [March 19, 2009, 3:00pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025 "2009-03-19T15:00:31Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [March 19, 2009, 3:00pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/1 "2009-03-19T15:00:31Z")
Have there been any studies that look at familial relationships and sexual preference? That is, “if you have a gay uncle you’re 12% more likely to be gay yourself”…something like that. I was watching a TV show where one of the characters is gay, has a gay uncle, and it was just revealed that his long-lost father (not related to the uncle) is gay as well. It brought to mind a person I know who has a sister and a brother who are both gay. So I was wondering if there have been many studies on the topic. I also had the thought that such a study might be hard to carry out because, to my knowledge, admitting one’s homosexuality doesn’t go back too many generations just yet. So it might be hard to know if someone’s great grandpa was gay or not. ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [March 19, 2009, 3:04pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/2 "2009-03-19T15:04:32Z")
I’d give that a higher probability than the one about sterility being inherited. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [March 19, 2009, 3:28pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/3 "2009-03-19T15:28:27Z")
The only statistic I’ve ever heard is that there’s a high probability that the mother of a gay man was previously pregnant with a male (not the same as “having an older brother”). ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [March 19, 2009, 3:56pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/4 "2009-03-19T15:56:02Z")
> **[Biology and sexual orientation | Twin studies](https://en.wikipedia.org/wiki/Biology_and_sexual_orientation#Twin_studies)** > > A number of twin studies have attempted to compare the relative importance of genetics and environment in the determination of sexual orientation. In a 1991 study, Bailey and Pillard conducted a study of male twins recruited from "homophile publications", and found that 52% of monozygotic (MZ) brothers (of whom 59 were questioned) and 22% of the dizygotic (DZ) twins were concordant for homosexuality. 'MZ' indicates identical twins with the same sets of genes and 'DZ' indicates fraternal twins A 2... ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [March 19, 2009, 4:16pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/5 "2009-03-19T16:16:28Z")
There was recent research announced finding that boys with a large number of older brothers were liklier to be gay. Don’t remember a cite, tho. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [March 19, 2009, 4:17pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/6 "2009-03-19T16:17:45Z")
Interesting **Sage Rat** , thanks. It seems like the studies done on twins shows that there’s so little genetic correlation between twins and siblings that it’s not worth looking outwards on the family tree for more connections. ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 19, 2009, 4:55pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/7 "2009-03-19T16:55:33Z")
> [@panache45](#): > > The only statistic I’ve ever heard is that there’s a high probability that the mother of a gay man was previously pregnant with a male (not the same as “having an older brother”). That’s strange. What could that possibly have to do with a child’s genetic makeup? Your genetic material is 50% from Mom and 50% from Dad regardless of the previous pregnancies of Mom. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 19, 2009, 4:59pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/8 "2009-03-19T16:59:01Z")
It wouldn’t have an impact on the subsequent child’s genetic makeup, but it could have an impact on the hormonal environment in the womb. Remember, there’s a difference between “homosexuality is genetic” and “homosexuality is inborn”. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [March 19, 2009, 5:00pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/9 "2009-03-19T17:00:52Z")
> [@jtgain](#): > > That’s strange. What could that possibly have to do with a child’s genetic makeup? Your genetic material is 50% from Mom and 50% from Dad regardless of the previous pregnancies of Mom. That’s got to be a social factor, not a bio factor. I’d suggest adultery as a factor, but there’s no reason to believe that the milkman’s kids would be any likelier gay than the guy who actually lives with mom… ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [March 19, 2009, 5:02pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/10 "2009-03-19T17:02:17Z")
> [@Chronos](#): > > It wouldn’t have an impact on the subsequent child’s genetic makeup, but it could have an impact on the hormonal environment in the womb. Remember, there’s a difference between “homosexuality is genetic” and “homosexuality is inborn”. Oood! Good save! Medicine and biology is weird. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [March 19, 2009, 5:19pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/11 "2009-03-19T17:19:27Z")
> [@ZipperJJ](#): > > Interesting **Sage Rat** , thanks. > > It seems like the studies done on twins shows that there’s so little genetic correlation between twins and siblings that it’s not worth looking outwards on the family tree for more connections. True, 30% between identical twins isn’t a big link. But it does show that there is a genetic factor to homosexuality. If there wasn’t that number would be 5%, the same as the rest of the population. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [March 19, 2009, 5:29pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/12 "2009-03-19T17:29:18Z")
The more I think about it, though, the more I think it’s just impossible to get a really solid study. Hair color, eye color, skin color, diseases, etc…all that stuff can’t be faked. Sexual preference can be suppressed or lied about…or just plain left out of record. Seems like the only people who can be in the study are people who are willing to admit their sexual preference but that leaves out a whole swath of folks who aren’t. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [March 19, 2009, 5:46pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/13 "2009-03-19T17:46:14Z")
> [@ZipperJJ](#): > > The more I think about it, though, the more I think it’s just impossible to get a really solid study. > > Hair color, eye color, skin color, diseases, etc…all that stuff can’t be faked. Sexual preference can be suppressed or lied about…or just plain left out of record. Seems like the only people who can be in the study are people who are willing to admit their sexual preference but that leaves out a whole swath of folks who aren’t. Well plus it could be that only 2% of anyone has a true, biological preference (for example), 1% homosexual, and 1% heterosexual, and everyone else is pretty free floating and just adopting whatever their brain latches onto via environment. In that case, with almost everyone being open to whatever, it would make it very hard to find the signal amongst the noise. 80% of everyone who listed themselves as gay would be non-genetically gay. But that would match up pretty closely with what the twin study is showing. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [March 19, 2009, 11:16pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/14 "2009-03-19T23:16:41Z")
> [@jtgain](#): > > That’s strange. What could that possibly have to do with a child’s genetic makeup? Your genetic material is 50% from Mom and 50% from Dad regardless of the previous pregnancies of Mom. I didn’t say it was genetic. It’s possible that there are certain hormones that either come into play (or stop coming into play) once a woman has carried a male fetus. Even if the fetus is aborted, or carried to term and adopted out, the statistic remains the same. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [March 20, 2009, 6:53am UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/15 "2009-03-20T06:53:57Z")
> [@ZipperJJ](#): > > Have there been any studies that look at familial relationships and sexual preference? Since most of your question has been answered by the various studies cited, it might be time to point out that the term you used, _sexual preference_ is considered as rather a loaded, almost derogatory term. (Not that I think you meant it that way.) The preference part asserts that this is a choice, rather than an inborn characteristic. And that is a hotly debated topic right now (though, IMO, studies like the ones cited seem to conclude that debate). The term _sexual preference_ is used mostly by right-wing fundamentalists now; otherwise the more neutral _sexual orientation_ is used. Or even the simpler term _sexuality_. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [March 20, 2009, 1:43pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/16 "2009-03-20T13:43:22Z")
Thanks, I do appreciate the correction. ---
**Author:** ![chaoticbear](https://avatars.discourse-cdn.com/v4/letter/c/f07891/32.png) [@chaoticbear](https://boards.straightdope.com/u/chaoticbear)\ **Post date:** [March 20, 2009, 2:00pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/17 "2009-03-20T14:00:40Z")
> [@t-bonham@scc.net](#): > > Since most of your question has been answered by the various studies cited, it might be time to point out that the term you used, _sexual preference_ is considered as rather a loaded, almost derogatory term. (Not that I think you meant it that way.) > > The preference part asserts that this is a choice, rather than an inborn characteristic. And that is a hotly debated topic right now (though, IMO, studies like the ones cited seem to conclude that debate). > > The term _sexual preference_ is used mostly by right-wing fundamentalists now; otherwise the more neutral _sexual orientation_ is used. Or even the simpler term _sexuality_. Lol, sometimes I hate the SDMB! I was going to post about the mother-carrying-another-male study and the identical twins study AND post a comment like this. 😉 Damn busy-work powerpoint presentations for liberal arts classes. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [March 21, 2009, 2:50pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/18 "2009-03-21T14:50:14Z")
There is another kind of inborn characteristic that is kind of between genetics and uterine environment, called epigenetics. As I recall reading a couple years ago, the point here is that there are mechanisms outside the standard so many chromosomes we’ve heard about for decades. This mechanism accepts influences from the environment and provides signals that get used for several generations. It sounds almost like that example of what does NOT happen, the one where chopping the tails off of 20 generations of mice does not cause the 21st generation to be genetically tailless. The example I remember from epigenetics was that if your great grandfather was almost starving through his adolescence and starting parenthood, you will have a measureably different inborn tendency for things like metabolic rate and fat storage and hunger. Not sure if I remember this correctly but I think this mechanism used DNA- or RNA-like molecules to carry its message. However, they were stray bits or attached elsewhere, not the nuclear chromosomes we all know about. ---
**Author:** ![booklover](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@booklover](https://boards.straightdope.com/u/booklover)\ **Post date:** [March 21, 2009, 6:31pm UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/19 "2009-03-21T18:31:56Z")
One of the studies that supports Napier’s comment about more older brothers being linked to a higher probability of homosexuality in men: [http://www.pnas.org/content/103/28/10771.full](http://www.pnas.org/content/103/28/10771.full) As a personal aside, I wish they would do cross-gender studies on this issue, or more studies with lesbians in them. I’m a lesbian with two bisexual grandparents and have often wondered whether there’s a link there. ---
**Author:** ![Moscow\_Discow](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Moscow\_Discow](https://boards.straightdope.com/u/Moscow_Discow)\ **Post date:** [March 22, 2009, 4:00am UTC](https://boards.straightdope.com/t/genealogy-sexual-preference/490025/20 "2009-03-22T04:00:37Z")
Anecdotally, of my generation in my own family (there are 5 of us), 3 are gay. My best (lesbian) friend’s girlfriend and her older brother were also both gay.