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.
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.
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.
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.
I’m Asian and I float like a brick.
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.
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
This study appears to better support the idea that added fat is not helpful for swimmers: http://www.pponline.co.uk/encyc/0346.htm
The latest theory I have read about is the “belly button theory”. 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.
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.”
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.
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.
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.
In Antifragile, meanwhile, Nassim Nicholas Taleb cites a study like this one 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.
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.”
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.
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.
A point well made but there is this bit
Not sure if it has been followed up on.
No, Napier’s bones are good at math.