# odds of having 11 children of the same sex **URL:** \ **Category:** Factual Questions\ **Created:** [May 7, 2010, 7:19am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610 "2010-05-07T07:19:32Z")\ **Posts on this page:** 17\ **Page:** 3
**Author:** ![Electric\_Monk](https://avatars.discourse-cdn.com/v4/letter/e/2acd7d/32.png) [@Electric\_Monk](https://boards.straightdope.com/u/Electric_Monk)\ **Post date:** [May 7, 2010, 10:44pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/41 "2010-05-07T22:44:26Z")
My father was the oldest of 11 boys, no girls. Didn’t seem to be a gender bias in the next generation, though. ---
**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\ **Post date:** [May 7, 2010, 10:50pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/42 "2010-05-07T22:50:37Z")
This is a common statistical mistake (maybe even has a name, but can’t find it right now). The equation that states “the odds of X occurring are 1:Y therefore the odds of X occuring N times is Y to the power of N”, is only correct if the odds are always 1:Y. For most real world cases the odds of X occurring once may be 1:Y but once X has occurred the chances of it occurring again drop dramatically (and likewise for the third, fourth, etc. occurrence). Most likely as others have pointed out there is a genetic predisposition to producing children of a particular gender, so by the time she had 10 kids that were all boys the chances of the 11th one being a boy are nowhere near 50:50. ---
**Author:** ![Balance](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@Balance](https://boards.straightdope.com/u/Balance)\ **Post date:** [May 8, 2010, 12:20am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/43 "2010-05-08T00:20:34Z")
> [@Chronos](#): > > If that were the case, then the father would be already dead. It’s not that you need two copies of a recessive gene for it to be active; it’s that you need to not have a dominant gene. Since the Y chromosome contains almost nothing, a man with a recessive gene on his X will always express it. This is why hemophilia and colorblindness, among others, are so much more common in men than women. Fair point. For the sake of the hypothetical, I was assuming that the recessive was something that _could_ be masked by the Y chromosome somehow. It does seem highly unlikely that such a thing actually exists, though. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [May 8, 2010, 2:28am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/44 "2010-05-08T02:28:36Z")
> [@CookingWithGas](#): > > :dubious: If I do that, will my post count get that high too? Not have kids? Very likely. You’ll have more time for the Dope that way. 😉 ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [May 8, 2010, 3:32am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/45 "2010-05-08T03:32:13Z")
WOOOO! I’m not having kids like a motherfuck! ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [May 8, 2010, 4:18am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/46 "2010-05-08T04:18:10Z")
> [@Bosstone](#): > > First we must assume all the children are spheres. In a vacuum. Incidentally, if there was some biological mechanism in play, it isn’t necessarily on the father’s side. I can imagine a woman who spontaneous aborts XY embryos while keeping XX ones (or vice-versa) who may not even be aware of how many rejected embryos she is tossing. ---
**Author:** ![Autolycus](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Autolycus](https://boards.straightdope.com/u/Autolycus)\ **Post date:** [May 8, 2010, 7:39am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/47 "2010-05-08T07:39:48Z")
If a woman has 10 male children, what are the odds that the 11th will be Hitler? ---
**Author:** ![Hilarity\_N.Suze](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hilarity_n.suze/32/6223_2.png) [@Hilarity\_N.Suze](https://boards.straightdope.com/u/Hilarity_N.Suze)\ **Post date:** [May 8, 2010, 7:59am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/48 "2010-05-08T07:59:05Z")
I read somewhere–maybe here?–that having given birth to a child of one sex, you are slightly more likely to give birth to subsequent children of that same sex, whatever it is. In other words, that there are slightly more families with multiple siblings of the same sex than with multiple siblings of both sexes. This is certainly true in my family. Among my cousins there is a preponderance of boys. But the one who had girls had ONLY girls. The rest had only boys. (I have four.) ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 8, 2010, 11:46am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/49 "2010-05-08T11:46:22Z")
> [@Hilarity\_N.Suze](#): > > I read somewhere–maybe here?–that having given birth to a child of one sex, you are slightly more likely to give birth to subsequent children of that same sex, whatever it is. > In other words, that there are slightly more families with multiple siblings of the same sex than with multiple siblings of both sexes. The second statement doesn’t follow from the first, unless you confine the discussion to families with just two children. ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [May 8, 2010, 4:34pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/50 "2010-05-08T16:34:37Z")
> [@Cat\_Whisperer](#): > > I come from a family of five girls. Everyone I know with kids has one sex only, no mixed bags. The idea that men produce one sex over the other and resist regular probability seems plausible to me. You have never **in your life** met someone with kids of both genders? ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [May 8, 2010, 5:58pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/51 "2010-05-08T17:58:57Z")
Well, that isn’t what I said, was it? I said everyone I know - at the moment, I know a handful of people with kids, and every one of them has a single gender. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [May 8, 2010, 8:51pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/52 "2010-05-08T20:51:59Z")
> [@Cat\_Whisperer](#): > > I come from a family of five girls. Everyone I know with kids has one sex only, no mixed bags. The idea that men produce one sex over the other and resist regular probability seems plausible to me. Plausible maybe but your sample size is too small to be meaningful. ---
**Author:** ![Biffy\_the\_Elephant\_Shrew](https://avatars.discourse-cdn.com/v4/letter/b/e47c2d/32.png) [@Biffy\_the\_Elephant\_Shrew](https://boards.straightdope.com/u/Biffy_the_Elephant_Shrew)\ **Post date:** [May 8, 2010, 9:40pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/53 "2010-05-08T21:40:19Z")
> [@Bosstone](#): > > First we must assume all the children are spheres. > [@Bryan\_Ekers](#): > > In a vacuum. On a frictionless treadmill. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [May 8, 2010, 9:42pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/54 "2010-05-08T21:42:47Z")
> [@Biffy\_the\_Elephant\_Shrew](#): > > On a frictionless treadmill. Singing “Rio” by Duran Duran. ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [May 9, 2010, 1:15am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/55 "2010-05-09T01:15:11Z")
> [@CookingWithGas](#): > > Plausible maybe but your sample size is too small to be meaningful. Sure enough, but it’s the only sample size I got. 🙂 ---
**Author:** ![Autolycus](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@Autolycus](https://boards.straightdope.com/u/Autolycus)\ **Post date:** [May 9, 2010, 6:18am UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/56 "2010-05-09T06:18:14Z")
> [@Elendil\_s\_Heir](#): > > Singing “Rio” by Duran Duran. Ah, it’s 1920’s pregnancy rays. ---
**Author:** ![kimera](https://avatars.discourse-cdn.com/v4/letter/k/f0a364/32.png) [@kimera](https://boards.straightdope.com/u/kimera)\ **Post date:** [May 9, 2010, 2:45pm UTC](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610/57 "2010-05-09T14:45:48Z")
Let’s not forget that it isn’t just the male who controls the sex of the offspring. The Trivers-Willard Hypothesis states that high-quality females are more likely to produce male offspring while low-quality females are more likely to produce female offspring, especially in polygynous species. The reasoning for this is that a low quality female is still likely to at least produce some offspring, while a low quality male is unlikely to produce any offspring. This is seen in a variety of species such as red deer and macaques (although any primate data is still controversial). There’s even possible explanations for why this occurs: [high levels of glucose favor the survival of male blastocysts](http://www.pnas.org/content/98/17/9677.abstract) [Parental hormontal levels around time of conception control mammalian sex ratios](http://humrep.oxfordjournals.org/cgi/reprint/19/6/1250). [Female testosterone level is important](http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WMD-4N3P0CS-1&_user=10&_coverDate=06/21/2007&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=b7fd18e5da23128780bbdcf21f13609b) [Female mice fed a high-fat diet had a sex ratio of .67 (male preference) while mothers on a low fat, high carb diet had a ratio of .39 (female preference](http://www.pnas.org/content/100/8/4628.full.pdf+html) There is some evidence this occurs in humans (although it’s highly debated). See: [Sex-ratio biasing towards daughters among lower-ranking co-wives in Rwanda](http://rsbl.royalsocietypublishing.org/content/5/6/765.full.pdf+html). [A study on sex-ratios lowering after 9-11 due to evidence which suggests that the ratio of males to females falls when mothers are stressed](http://humrep.oxfordjournals.org/cgi/reprint/20/5/1221). Then, there are some species where the females have high rank which they pass down through their daughters; or females need to control large patches of land, so high quality females have a much greater reproductive success, etc, and in these species, we would find a preference for daughters expressed. Tawny owls, for example, lay [female-biased clutches on territories with more abundant prey](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1688563/). There’s also environmental factors to take into play, such that certain conditions are more likely to produce offspring of a certain sex. Males are more fragile than females and male babies are conceived more and aborted more. In areas with high levels of pollution, the male to female ratio drops. [Cite.](http://linkinghub.elsevier.com/retrieve/pii/S014067360002290X) [Cite.](http://www.ncbi.nlm.nih.gov/pubmed/1428486) It makes sense that certain females might express preferences for a sex of certain offspring. Sometimes, producing more of one sex can be highly beneficial and, if there are no selective pressures away from this sex preference, it will be maintained and passed on through the daughters. [Previous page](https://boards.straightdope.com/t/odds-of-having-11-children-of-the-same-sex/538610.md?page=2)