# Gestation period different for different races? **URL:** \ **Category:** Factual Questions\ **Created:** [April 19, 2001, 9:48am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519 "2001-04-19T09:48:25Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Badtz\_Maru](https://avatars.discourse-cdn.com/v4/letter/b/e36b37/32.png) [@Badtz\_Maru](https://boards.straightdope.com/u/Badtz_Maru)\ **Post date:** [April 19, 2001, 9:48am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/1 "2001-04-19T09:48:25Z")
I heard that the average gestational period varies somewhat among different races of people, that it tends to be shorter by a week or two for Asians. I can’t seem to find anything about this on google so it’s probably false, but sometimes I miss things so…does anyone know if this claim has any basis in fact? ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [April 19, 2001, 1:09pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/2 "2001-04-19T13:09:16Z")
[sigh] calling Collounsbury… um, maybe the reason you couldn’t find anything is because there’s no such thing as “race” when it comes to _homo sapiens_? 😉 ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [April 19, 2001, 1:14pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/3 "2001-04-19T13:14:41Z")
Koreans tend to belive gestation for a fetus is 10 months… this is due to some Confusian deal…they think that, at conception, the fetus is one month old… it’s BS, IMHO, but there it is… Similarly, a baby, at birth, is 1 years old… leading to some confusian between foreign teachers and Koreans. Some Asian societies measure age based on the lunar calendar, not the solar calensar… ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [April 19, 2001, 2:08pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/4 "2001-04-19T14:08:50Z")
I was going to ignore this, but since I have been summoned: I have seen two citations to studies purporting to establish “racial” differences – in the cases I saw I did not see an adequate addressing of the assumed racial categories. Rather the researchers appear to have assumed human races as valid units and worked from there, without adequately addressing a range of environmental considerations. Poor research design. Rather like the Redheaded neandertal thingy. From a theoretical perspective, to have differences in racial gestation periods based on inherent biological differences one would expect that there were some kind of fixed differences between races. I think we’ve been over that ground rather enough to know the answer. However, “racial” differences may very well be capturing something non-genetic per se. It might be true that some specific populations, biologically defined, may have a tendency towards shorter or longer gestation period, but one would suspect that the issue is largely environmentally determined. I’ll leave it to medical professionals to expand upon this. So the short answer might best be stated as probably not true, although there may be a grain of truth insofar as regionally defined enviromental conditions (including cultural practices) might have a significant impact on average gestation times. ---
**Author:** ![labdude](https://avatars.discourse-cdn.com/v4/letter/l/5fc32e/32.png) [@labdude](https://boards.straightdope.com/u/labdude)\ **Post date:** [April 19, 2001, 2:10pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/5 "2001-04-19T14:10:52Z")
Are you confusing gestation with the onset of puberty. IIRC, the average on set of puberty is sightly different for blacks, whites, and asians. Sorry no source. * * * and off we go once again to GD/PIT to once again argue that race doesn’t exist. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [April 19, 2001, 2:15pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/6 "2001-04-19T14:15:25Z")
> [@](#): > > \*Originally posted by labdude \* > > * * * > > and off we go once again to GD/PIT to once again argue that race doesn’t exist. Shrug, biologically it doesn’t. I think we can stay out of GD or the Pit at this point. BM asked a factual question. It appears with perhaps one exception, the replies have addressed his question. ---
**Author:** ![Lamia](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lamia](https://boards.straightdope.com/u/Lamia)\ **Post date:** [April 19, 2001, 2:37pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/7 "2001-04-19T14:37:23Z")
Is it possible that a woman’s diet could affect the length of time she is pregnant? If there really is a difference in gestation periods between people from different places then that might be why. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [April 19, 2001, 3:08pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/8 "2001-04-19T15:08:47Z")
Lamia: One can certainly postulate that is the case, see e.g. Lindsay H. Allen _Biological Mechanisms That Might Underlie Iron’s Effects on Fetal Growth and Preterm Birth_ Journal of Nutrition. 2001;131:581S-589S. [http://www.nutrition.org/cgi/content/abstract/131/2/581S](http://www.nutrition.org/cgi/content/abstract/131/2/581S) (full text is subscription) That of course does not mean ipso facto this entirely explains regional/ethnic/population differences, only that the mechanism certainly appears to exist and must be accounted for. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [April 19, 2001, 6:12pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/9 "2001-04-19T18:12:59Z")
> [@](#): > > \*Originally posted by Astroboy14 \* > \*\*Koreans tend to belive gestation for a fetus is 10 months… this is due to some Confusian deal…they think that, at conception, the fetus is one month old… it’s BS, IMHO, but there it is… > \*\* Um, the gestation period for humans _is_ ten months, or 40 weeks. A baby born at 36 weeks is early. Arjuna34 ---
**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:** [April 19, 2001, 9:12pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/10 "2001-04-19T21:12:32Z")
Check your numbers, **Arjuna34**. 40 weeks is 9.2 months. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [April 19, 2001, 9:38pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/11 "2001-04-19T21:38:00Z")
Hmm, I guess it depends on how you define “month”. If you call a month “four weeks = 28 days”, then of course 40 weeks is 10 months. If you define a month as “365.25/12 = 30.42 days”, then it’s 9.2 months. Arjuna34 ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [April 19, 2001, 11:33pm UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/12 "2001-04-19T23:33:01Z")
**Arjuna34** That 40 week/10 month stuff is propagated by the medical profession because they fear their patients are mathphobic. (joke) Only one month of the calendar is 28 days, and that not all the time. And, actually, the gestation period is 38 weeks, from time of conception–they count the 40 week period from the start of the last menstruation, adding about two weeks. That’s all average anyway. **Astroboy14** Do you have some citations to back that all up? It seems off to me–why go to the trouble of saying a fetus is one month old at conception, then count nine more, and call it a year? ---
**Author:** ![Autumn\_Wind\_Chick](https://avatars.discourse-cdn.com/v4/letter/a/6a8cbe/32.png) [@Autumn\_Wind\_Chick](https://boards.straightdope.com/u/Autumn_Wind_Chick)\ **Post date:** [April 20, 2001, 12:43am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/13 "2001-04-20T00:43:18Z")
I wouldn’t be surprised if time of gestation varied a little by race. There is evidence that other things having to do with reproduction and fertility vary by race, such as the incidence of fraternal twins. (Blacks are more likely to have fraternal twins than whites; asians are less likely to have fraternal twins than whites.) ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [April 20, 2001, 3:07am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/14 "2001-04-20T03:07:07Z")
**Autumn Wind Chick** , if you have an actual citation to a genuine scholarly journal supporting that assertion, we would be very interested in seeing it. Otherwise, I believe we will consider your statement to be another example of the various folk tales that people keep attributing to different (ill-defined) populations. I am, in all seriousness, not trying to mock you, but we have been through a number of claims for “racial” identity in the last few months and have found no such statement that has stood up to rigorous scientific analysis. ---
**Author:** ![Zarathustra](https://avatars.discourse-cdn.com/v4/letter/z/898d66/32.png) [@Zarathustra](https://boards.straightdope.com/u/Zarathustra)\ **Post date:** [April 20, 2001, 3:25am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/15 "2001-04-20T03:25:53Z")
> [@](#): > > \*Originally posted by tomndebb \* > \*\*I am, in all seriousness, not trying to mock you, but we have been through a number of claims for “racial” identity in the last few months and have found no such statement that has stood up to rigorous scientific analysis. \*\* So there’s no such thing as an epicanthic fold? Or sickle-cell anemia? Or melanin, for that matter? ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [April 20, 2001, 4:01am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/16 "2001-04-20T04:01:57Z")
Epicanthic folds occur in a number of different populations, none of which can be construed as a race. Sickle-cell occurs among a large number of groups (many of whom would be classically described as “Caucasian” or “Mongoloid”) who live in areas of endemic malaria. In the U.S. it is considered a “black” disease because the majority of slaves were imported from the high-malaria regions of Africa while the majority of the “Caucasians” in the U.S. came from regions where malaria was not sufficiently prevalent to invoke that genetic trait. Dark skin occurs in every single group that was classically described as a “race” including “Caucasians” in the southern Indian subcontinent and “Mongoloids” in the Andaman islands as well as whatever different “races” one would choose to throw aboriginal Australians and natives of Fiji. Believe me, we _have_ been through this before. Before we get started on this one more time (dragging it inevitably to **Great Debates** and exhausting the patience of **Collounsbury** , **edwino** , and numerous others), please take the time to read over at least _some_ of the links provided on the FAQ on this page: [Does Race Exist? NO.](http://www.eneubauer.com/) Please note: the concept that there are populations of humans that have unique features that can be coherently identified is real. No one claims that “all people are exactly alike.” However, the problem occurs when one attempts to use the word “race” (which has a clear intention of describing a very few groups of people with very large populations) to classify people. No such large groups exist. There are enough differences among “blacks” or “whites” or whomever and enough shared characteristics _between_ “blacks” and “whites” or whomever that the word “race” has no useful biological meaning. Occasionally, one will see a “study” showing that some group of people in the Limpopo Valley in Africa or some other group of people among the Transylvanian Magyars have a genuine, genetically identified characterisitc. What usually happens at that point is that some unscholarly person with an agenda will point to the Riparian Limpopo study and say “blacks are _x_” or point to the montagnan Transylvanians and say “whites are _y_” when the reality is that only the Limpopoans or Transylvanians have the discovered characteristics. We are not being obtuse or PC or anything else. If you read the actual studies linked, you will discover that “race” does not have a valid, coherent biological meaning. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [April 20, 2001, 4:04am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/17 "2001-04-20T04:04:22Z")
> [@](#): > > \*Originally posted by Zarathustra \* > **So there’s no such thing as an epicanthic fold? Or sickle-cell anemia? Or melanin, for that matter?** That doesn’t follow. They’re apparently not indicative enough, though. ACK! **labdude** , I’m sorry. ---
**Author:** ![Terminus\_Est](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/terminus_est/32/3087_2.png) [@Terminus\_Est](https://boards.straightdope.com/u/Terminus_Est)\ **Post date:** [April 20, 2001, 4:30am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/18 "2001-04-20T04:30:51Z")
**tomndebb** Diamond, JM (1986) Variation in human testis size. Nature (London) 320: 488-489 > [@](#): > > The frequencies of dizygotic twins are even higher (up to 49 per 1,000 births) among African blacks. … Yoruba women, with the world’s highest frequency of dizygotic twins, have higher FSH and LH levels at the time of ovulation than do Japanese women, who have the lowest frequency of dizygotic twins. Rushton, J.P. & Bogaert, A.F. (1987) Race differences in sexual behavior: Testing an evolutionary hypothesis. Journal Research in Personality 21(4): pp. 534 > [@](#): > > While the monozygotic twinning rate is nearly constant at about 3 1/2 per 1000 in all groups, dizygotic twinning (the r-strategy) is greater among lower than upper social class women in both European and African samples (Golding, 1986; Nylander, 1981). Also, the rate per 1000 births among Mongoloids is \<4; among Caucasoids, 8; and among Negroids, \>16, with some African populations having rates as high as 57 per 1000 (Bulmer, 1970). The incidence of nonmonozygotic triplets and quadruplets shows comparable rank orders. Moreover, data from racially mixed matings suggest that the mother independently of the race of the father, as shown for Mongoloid-Caucasoid crossings in Hawaii, and Caucasoid-Negroid crosses in Brazil (Bulmer, 1970). Note that I have _not_ read the articles in question. I simply did a quick Google search and came up with this page: [http://www.neoteny.org/a/twins.html](http://www.neoteny.org/a/twins.html) ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [April 20, 2001, 4:57am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/19 "2001-04-20T04:57:52Z")
**Terminus Est** , I thank you for providing a real-life example of my point. (And I am not being sarcastic.) Note that in the 1986 _Nature_ article, the comparison is made between two specific _ethnic_ groups, the Yoruba and the Japanese (probably excluding the Ainu simply because they tend to get left out of these things–but that is my conjecture), but the conclusion drawn is to “African blacks” in general vs (probably?) Asians in general. Without similar studies of the Ibo, Masaai, etc. and the various ethnic groups among all the peoples of Southeast Asia, we do not really know what the incidence of twinning is for the larger populations. Note that these studies are all over 15 years old. Most of the genetic studies that have destroyed the concept of race are much more recent. It would have been “natural” for a researcher in 1986 (to say nothing of 1970) to extrapolate from small populations to what was, at that time, perceived to be the larger populations. However, with the studies of the last 10 years or so, we now know that those “natural” (actually, culturally based) assumptions and extrapolations are not based in fact. In the second citation, you will note that the general conclusion seems to be that _class_ (translated to quality of diet, perhaps?) is the significant factor, with further numbers drawn from supposed racial groups (which might possibly map out along dietary lines, as well). We also do not have the raw statistics in the second citation. If the small ethnic group, the Yoruba, have an extremely high rate of twinning (which _might_ be genetic), it is possible that their numbers elevated the overall numbers for Africa while a further study of Africa, broken down by each ethnic group, would show only the Yoruba as a high-twinning population. In other words, we have, indeed, been presented with observations that link twin births to (culturally identified) racial groups, (for which I thank you), but a review of the evidence seems to indicate that other factors than _race_ were the actual determinants. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [April 20, 2001, 8:18am UTC](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519/20 "2001-04-20T08:18:01Z")
Obviously these answers are not the sort the OP was looking for. Below I’ll quote the sort of answer he was looking for and after I’m gone you can debate the meaninglessness of it all. > [@](#): > > For some reason we do not understand, female babies on average spend a day longer inside their mother’s bodies than their male counterparts. And white babies on average spend five days longer inside than black babies. In India, the average gestation period is even longer, Indian babies spending six days more inside their mothers than typical white babies. These differences are purely racial and have nothing to do with the size of the babies, or the affluence or poverty of the families concerned. > Desmond Morris, _Babywatching_ For the record, Desmond Morris is not my preferred source of information on any subject, but it was the best I could find. [Next page](https://boards.straightdope.com/t/gestation-period-different-for-different-races/62519.md?page=2)