# African-Americans have dense bones & sink easily, Asians have porous bones & they float. T or F? **URL:** \ **Category:** Factual Questions\ **Created:** [September 11, 2013, 1:39am UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541 "2013-09-11T01:39:46Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 11, 2013, 11:53am UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/21 "2013-09-11T11:53:05Z")
> [@WhyNot](#): > > Weight? I know heavier people tend to less osteoporosis than underweight people, giving the bones the benefit of weight bearing and impact to stimulate the osteoblasts (if I recall my physiology classes correctly). African Americans certainly average a higher BMI than Asians. (Again, as a group, generalization, here, have this broad brush…) Weight was controlled for in most of the studies I found (and in the ones Tom linked to). Weight and BMI were associated with bone mineral density and indeed those differences explained some portion of the difference, but after controlling for those body composition variations most of the bone mineral denisty differences remained. > [@Tom's second link](#): > > Our large, population-based study had sufficient power to detect racial differences in clinical and biochemical variables on the order of 0.5 standard deviations. Clinical and biochemical assessment was extensive and enabled us to study a comprehensive list of variables that others have considered relevant to bone mass. After multiple adjustments for these variables, about half the racial differences in BMD still remained. This finding suggests that other factors than those controlling muscle mass and body size must act specifically on the skeleton. > > We conclude that racial differences in BMD are established early in childhood (33) and are not explained by clinical and biochemical variables measured in young adulthood. Studies of adolescents might find differences in metabolic or lifestyle factors that account for a larger share of the racial differences in bone mass than those that we observed. By midadolescence, black boys and girls have 10–15% greater bone density than their white counterparts (33). ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [September 11, 2013, 1:13pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/22 "2013-09-11T13:13:54Z")
Never heard this one. The A-A propensity to sink I have heard attributed to body fat. Unless you bone up(sorry) on a pizza and coke diet, all other things being equal, a race evolved for tropical conditions has significantly less body fat _ **on average** _ than one developed for northern climates. Of course, whoever dreamed up this excuse never considered some of the more interesting cases from Jersey city - but even if those ladies floated like an ice cream sundae, they ain’t winnin’ no swimmin’ speed race. However, ignoring bone density, muscle is more dense than fat, and having a decent body-fat ratio will help with buoyancy, while being lean and muscular helps with sinking and running and other strength contests. Or it may all be racial BS and very few black athletic types in high school have access to Olympic sized pools to do the 4-plus hours a day of training needed to be Olympic calibre, although there’s no shortage of basketball courts. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [September 11, 2013, 1:27pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/23 "2013-09-11T13:27:22Z")
Flotation isn’t a factor for competitive racers, so while those arguments might be meaningful for recreational swimmers it doesn’t really hold water for racers. While not extremely cut athletes in some other disciplines, swimmers have lots of muscle and relatively little fat, no matter their ethnic heritage. ---
**Author:** ![PoorYorick](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@PoorYorick](https://boards.straightdope.com/u/PoorYorick)\ **Post date:** [September 11, 2013, 1:39pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/24 "2013-09-11T13:39:33Z")
In forensic anthropology, we were trained that African Americans did indeed have denser bones in general than other populations. Also, the surface is described as “ivorine.” From looking at bones myself, I can bear this out. You can tell the difference by holding the femur of an African American in one hand, and one from a Native American, for instance. Now, why this is so, I have no idea. ---
**Author:** ![DCnDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dcndc/32/2842_2.png) [@DCnDC](https://boards.straightdope.com/u/DCnDC)\ **Post date:** [September 11, 2013, 1:53pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/25 "2013-09-11T13:53:45Z")
I’m Asian and I float like a brick. ---
**Author:** ![foopyx](https://avatars.discourse-cdn.com/v4/letter/f/3e96dc/32.png) [@foopyx](https://boards.straightdope.com/u/foopyx)\ **Post date:** [September 11, 2013, 2:04pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/26 "2013-09-11T14:04:35Z")
I know how much anecdotal evidence is shunned here, but I thought I’d chime in and saythat I can lay down flat on the bottom of a pool. 5’11 190lbs Korean (made in USA). Though my Korean girlfriend floats easily. 5’6 105lbs After my exhaustive reasearch, I’ve determined that 1 out of every 2 Asians float. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [September 11, 2013, 2:20pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/27 "2013-09-11T14:20:37Z")
> [@Telemark](#): > > Flotation isn’t a factor for competitive racers, so while those arguments might be meaningful for recreational swimmers it doesn’t really hold water for racers. While not extremely cut athletes in some other disciplines, swimmers have lots of muscle and relatively little fat, no matter their ethnic heritage. Even if an extra 1% or 2% effort is needed to prevent sinking, at olympic calibre events that’s probably the difference between winning and “close but no cigar”. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [September 11, 2013, 2:33pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/28 "2013-09-11T14:33:33Z")
> [@md2000](#): > > Even if an extra 1% or 2% effort is needed to prevent sinking, at olympic calibre events that’s probably the difference between winning and “close but no cigar”. An imperfect study, but [Sex differences in the centre of buoyancy location of competitive swimmers - PubMed](http://www.ncbi.nlm.nih.gov/pubmed/9663961) > [@](#): > > Therefore, our results do not support the notion that skilled male swimmers are at a performance disadvantage in terms of natural buoyancy characteristics. This study appears to better support the idea that added fat is not helpful for swimmers: [http://www.pponline.co.uk/encyc/0346.htm](http://www.pponline.co.uk/encyc/0346.htm) ---
**Author:** ![puddleglum](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puddleglum/32/137_2.png) [@puddleglum](https://boards.straightdope.com/u/puddleglum)\ **Post date:** [September 11, 2013, 3:05pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/29 "2013-09-11T15:05:57Z")
> [@md2000](#): > > Even if an extra 1% or 2% effort is needed to prevent sinking, at olympic calibre events that’s probably the difference between winning and “close but no cigar”. The latest theory I have read about is the “[belly button theor](http://www.slate.com/articles/health_and_science/human_nature/2010/07/lose_the_race.html)y”. This states that blacks have a higher center of mass when standing and that this gives them an advantage in sprinting and a disadvantage when swimming. The percentage difference is only 1.5% but at an Olympic level that is very large. ---
**Author:** ![bup](https://avatars.discourse-cdn.com/v4/letter/b/6bbea6/32.png) [@bup](https://boards.straightdope.com/u/bup)\ **Post date:** [September 11, 2013, 3:12pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/30 "2013-09-11T15:12:51Z")
> [@aceplace57](#): > > I’m not sure why, but I rarely (if ever) see African Americans in competitive swimming or diving competitions. ABC had a celebrity diving show last winter and a black football player made comments about not floating/swimming well. He struggled on that show. WAG - football players are gigantic (as are basketball players). Thus, the football player (don’t remember who that was) and Kareem Abdul-Jabar did not fare well on “Splash.” ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [September 11, 2013, 4:05pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/31 "2013-09-11T16:05:13Z")
> [@aceplace57](#): > > I’m not sure why, but I rarely (if ever) see African Americans in competitive swimming or diving competitions. …I wouldn’t be surprised to learn that bone density had something to do with it. Undoubtedly. It surely must also explain why I rarely see African Americans in competitive ice skating (hockey or figure) events. The small difference in average bone density must explain it, even if the range of individual variation within each group is much much greater than the difference in group averages. I suppose the dense bones keep them from skating as fast? Then again, I don’t see many people of Asian descent in competitive hockey either. Let’s see, it must be that their bones are too light and fragile? And of course the relative density of bones is why I rarely see people of African or European descent working in Chinese restaurants – the quick movements of cooking on a wok require less dense bones, right? And of course the U.S. Presidency requires bones of just the right density. ---
**Author:** ![tallcoldone](https://avatars.discourse-cdn.com/v4/letter/t/e9a140/32.png) [@tallcoldone](https://boards.straightdope.com/u/tallcoldone)\ **Post date:** [September 11, 2013, 4:25pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/32 "2013-09-11T16:25:23Z")
Breath management (in addition to the amount of body fat) is a large part of being able to float. The ability to relax and hold your breath when you’re in the water is very important (plus maybe total lung capacity). I have always been very comfortable in water and I can float easily, face up or down, with my lungs full. I sink quickly when I breathe out. If I was anxious, I would probably thrash around more, need to breathe more often, and have a harder time keeping my lungs full of air and be more likely to sink. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [September 11, 2013, 4:32pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/33 "2013-09-11T16:32:13Z")
Orthopaedic surgeons will tell you that the Young’s modulus (basically, stiffness) of Africans bones _tends_ to be higher than that of other ethnic groupings. IIRC the same is also true of Inuits. This doesn’t really tell you much, though, other than the fact that Africans are less likely to suffer fractures. ---
**Author:** ![biqu](https://avatars.discourse-cdn.com/v4/letter/b/7feea3/32.png) [@biqu](https://boards.straightdope.com/u/biqu)\ **Post date:** [September 11, 2013, 4:43pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/34 "2013-09-11T16:43:29Z")
In _Antifragile_, meanwhile, Nassim Nicholas Taleb cites a study like [this one](http://www.ncbi.nlm.nih.gov/pubmed/12856112) demonstrating a correlation between bone density and weight-bearing exercise (or lack thereof, in the case of master cyclists). If there’s a causal relation at work in such studies, equalizing the average bone density between populations might be as simple as getting more Africans interested in competitive cycling. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [September 11, 2013, 5:00pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/35 "2013-09-11T17:00:39Z")
Whoah. I can’t think of any mechanism by which that could occur. Body: “Hey, we’re on a bike again. Better shed some of this excess bone mass.” ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [September 11, 2013, 6:49pm UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/36 "2013-09-11T18:49:58Z")
> [@bup](#): > > WAG - football players are gigantic (as are basketball players). > > Thus, the football player (don’t remember who that was) and Kareem Abdul-Jabar did not fare well on “Splash.” Ndamukong “Cheap Shot” Suh? For awhile there I was thinking 😕 because I thought you were talking about Hines Ward, and he’s a bad example because he’s half Korean. But my mistake, he was on DWTS. Kareem is objectively huge. ---
**Author:** ![Honesty](https://avatars.discourse-cdn.com/v4/letter/h/f04885/32.png) [@Honesty](https://boards.straightdope.com/u/Honesty)\ **Post date:** [September 12, 2013, 1:40am UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/37 "2013-09-12T01:40:01Z")
> [@DSeid](#): > > Now why bone density varies is not immediately obvious to me … one would think with less sun getting through and lower vitamin D levels that density would be lower, not higher, in Blacks. The article speculates that there are hormonal differences. I don’t know. Since blacks require more sunlight to synthesize Vitamin D in the skin compared to whites, the accretion of calcium into bone must be a protective mechanism against bone loss from Vitamin D deficiency. - Honesty ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [September 12, 2013, 2:09am UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/38 "2013-09-12T02:09:04Z")
> [@Honesty](#): > > Since blacks require more sunlight to synthesize Vitamin D in the skin compared to whites, the accretion of calcium into bone must be a protective mechanism against bone loss from Vitamin D deficiency. > > - Honesty Not sure that theory holds up, because black pigmentation is apparently a defense against strong sunlight. So if you’re in a region with so much sunlight that you have to evolve a defense against it, vitamin D deficiency doesn’t seem like it would be a problem. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 12, 2013, 2:49am UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/39 "2013-09-12T02:49:50Z")
A point well made but there i[s this bit](http://onlinelibrary.wiley.com/doi/10.1359/jbmr.1999.14.5.740/full) > [@](#): > > Vitamin D Receptor Gene Fok1 Polymorphism Predicts Calcium Absorption and Bone Mineral Density in Children† > > … Children who were FF homozygotes had a mean calcium absorption that was 41.5% greater than those who were ff homozygotes and 17% greater absorption than Ff heterozygotes. BMD was 8.2% greater in the FF genotype than the ff genotype and 4.8% higher than the Ff genotype. These results suggest a substantial relationship between the VDR gene and bone metabolism at one or more levels, including dietary absorption of calcium and BMD in growing children. … > > … The prevalence of VDR alleles, as determined by the Fok1 polymorphism, has been determined for African-American women in one previous study.(21) We found 66.6% of the African-Americans in our study to be homozygous for the F allele and 33.4% to be Ff heterozygotes. This genotype distribution is similar to that reported by Harris et al.(21) (65% FF, 31% Ff, 4% ff). … It is interesting to speculate, however, that higher frequencies of the more favorable FF genotype (double that found for Caucasians and Mexican-Americans in our study) might partially explain the increased BMD seen in African-Americans, if similar allele frequencies are seen with larger study populations. Not sure if it has been followed up on. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [September 12, 2013, 4:39am UTC](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541/40 "2013-09-12T04:39:01Z")
> [@A\_nice\_guy\_with\_an\_opinion](#): > > Asian bones are good at math? Just trying to fit in here. No, [Napier’s bones](http://en.wikipedia.org/wiki/Napier%27s_bones) are good at math. [Previous page](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541.md?page=1) [Next page](https://boards.straightdope.com/t/african-americans-have-dense-bones-sink-easily-asians-have-porous-bones-they-float-t-or-f/668541.md?page=3)