The purpose of this study was to compare the mtDNA haplogroup data of elite groups of Jamaican and African-American sprinters against respective controls to assess any differences in maternal lineage. The first hypervariable region of mtDNA was haplogrouped in elite Jamaican athletes (N=107) and Jamaican controls (N=293), and elite African-American athletes (N=119) and African-American controls (N=1148). Exact tests of total population differentiation were performed on total haplogroup frequencies. The frequency of non-sub-Saharan haplogroups in Jamaican athletes and Jamaican controls was similar (1.87% and 1.71%, respectively) and lower than that of African-American athletes and African-American controls (21.01% and 8.19%, respectively). There was no significant difference in total haplogroup frequencies between Jamaican athletes and Jamaican controls (P=0.551 ± 0.005); however, there was a highly significant difference between African-American athletes and African-American controls (P<0.001). The finding of statistically similar mtDNA haplogroup distributions in Jamaican athletes and Jamaican controls suggests that elite Jamaican sprinters are derived from the same source population and there is neither population stratification nor isolation for sprint performance. The significant difference between African-American sprinters and African-American controls suggests that the maternal admixture may play a role in sprint performance.Reference: Deason et al. Scand J Med Sci Sports. 2011 Mar 16. doi: 10.1111/j.1600-0838.2010.01289.x. [Epub ahead of print]
[. . .]
Among African Americans, no individual haplogroup produced significant findings for Bonferroni-adjusted critical a of 0.003, presented in Table 3. Interestingly, the nonsub- Saharan paragroup was highly significant in overrepresentation within athletes. This may indicate an advantage possessed by more admixed individuals. While maternal admixture contributing any environmental and social advantages with regard to athletic training and development cannot be ruled out, further investigation into the amount of admixture in the autosomal genome is required to assess the overall non-African genomic component. In addition to assessing differences between athletes and controls in either group, the haplogroup distributions of Jamaican controls and African-American controls were also compared. These two populations were found to have significantly different haplogroup distributions (Po0.001), providing further mitochondrial evidence of different population histories. The matrilineal distribution of both athlete populations differs significantly, suggesting no discernable distribution of lineages indicative of elite sprinting in these genetically distinct groups of West African descent.
Elite Afr-Am sprinters more admixed than Afr-Am non-athletes?
Though hardly definitive, this study certainly lends no support to the notion that black dominance of short sprints in the US can be explained purely as a consequence of West African DNA.
The frequency of non-sub-Saharan haplogroups in Jamaican athletes and Jamaican controls was similar (1.87% and 1.71%, respectively) and lower than that of African-American athletes and African-American controls (21.01% and 8.19%, respectively).
ReplyDeleteIn simpler terms:
USA-Blacks, general: 8% non-Black
USA-Blacks, runners: 21% non-Black
.Jamaicans, general: 2% non-Black
.Jamaicans, runners: 2% non-Black.
These results do not make sense for two reasons.
1.) Why would non-Black genetic input improve sprinting ability?
2.) What sample of USA-Blacks would ever determine a mere 8% general non-Black input? Maybe the Louisiana Bayou, maybe South-Carolina, but generally USA-Blacks are 20% or so, according to every other study.
Hail,
ReplyDeleteThis study looks at only mtDNA. Almost certainly all 4 groups have higher levels of European autosomal DNA.
"Why would non-Black genetic input improve sprinting ability?"
The main point is that it certainly does not seem to diminish sprinting ability, though the result would have been more interesting had the authors also looked at autosomal DNA. Sprinting ability does not appear to be associated with any particular mtDNA haplogroup (only the non-African paragroup in the US black sample), so I doubt the effect has anything directly to do with mitochondrial energetics. Assuming black sprinters do have higher levels of white admixture than the general black population in the US, my guess would be the reason involves lung function or brain function (e.g., intelligence, work ethic) or nervous system efficiency more generally.
How about this: having white mtDNA indicates very recent mixture...and probably a flat-out white mother. Might this not signify superior nurture?
ReplyDeleten/a wrote:
ReplyDelete"This study looks at only mtDNA."
Thanks for the correction.
Maybe this study's results could be explained by a small share of US-Black sprinters having white mothers, rather than it being a general condition of the "average" USA-Black sprinter having noticeably-higher non-Black mtDNA.
In other words, how skewed are the results?
Of the study's population of 119 "elite African-American sprinters" 25 carry non-Black matrilineal lines (21.01%). If their mtDNA picture were identical to overall USA-Blacks' (8.19%), then only 9 or 10 of them would carry non-Black lines.
How to account for these 16 "extras"?
This is one way:
103 runners @ 8.2% avg non-Black mtDNA
16 runners @ 100% avg. non-Black mtDNA
...would give us a sample average of 20.5% non-Black mtDNA, near the 21% reported in the study. Yet, in this scenario, only a small few individuals (the 16 "biracials" with non-Black mothers) had any higher degree of non-Black mtDNA than the general population.
The ratio of ["Black-Sprinter mtDNA stock" to "Overall Black mtDNA stock"] is lopsided among USA-Blacks but equal among Jamaican-Blacks. This could be explained easily by lack of non-Black women in modern Jamaica, if my speculation outlined above is true.
If there is any validity to the speculation about skewed results from biracials, it points to cultural factors, not genetic ones.
George beat me to the punch by a few minutes with the same idea, although I'd point out: "having white mtDNA indicates very recent mixture" is not true. It could mean recent, or it could mean centuries ago, anytime after Blacks started to be brought west as slaves.
ReplyDeleteOne more thing, the study does not specify "white mtDNA", it includes all non-Black mtDNA lines.
So the football player Heinz Ward (Black father, South-Korean mother) would be part of this 21.1% non-Black mtDNA bloc.
Hi Hail. You have a nice blog.
ReplyDeleteI was too brief in my remarks. What I meant to imply is that in ostensibly full Blacks, there is a lot more white input along the patrilines since the offspring of slave women and white fathers would be incorporated into the black population, whereas black male-white female pairings were far more unacceptable in times gone by.
Contrariwise, these "African-Americans" with non-SSA mtDNA are more likely to have obvious, recent (maternal) Eurasian ancestry and are probably even self-identified as mixed.
George and Hail,
ReplyDeleteIf that turns out to be the case, it would still mean mulattoes are overrepresented compared to blacks in this sample of national-level US sprinters -- the conclusion again being that white genes seem strangely undetrimental to sprinting ability.
If that turns out to be the case, it would still mean mulattoes are overrepresented compared to blacks in this sample of national-level US sprinters -- the conclusion again being that white genes seem strangely undetrimental to sprinting ability.
ReplyDeleteThat is really interesting.
Any similar studies, or observations, on Mulatto/mixed-race sprinters from other parts of the world, ie - Africa, the Caribbean?
N/A, what can explain the fact that it is not seen in Jamaican Blacks? (Their sprinters have the exact same share of non-Black matrilineal lines as their general population). Simply a lack of sufficient non-black matrilineal ancestry among Caribbean Blacks?
ReplyDeleteI paid a lot of attention to sprinting in the 1990s, less since then. Most world class 100m men in the 1990s were quite black looking. Only Frankie Fredericks of Namibia, who looks a little like Alec Guinness, had obvious significant white ancestry.
ReplyDeleteOn the other hand, sociologically, sprinting in America is a more middle class black sport than is football or basketball. It's no longer a mainstream sport, and so it attracts men who don't like team sports or contact sports (gays, nerds, etc.)
It's no longer a mainstream sport, and so it attracts men who don't like team sports or contact sports (gays, nerds, etc.)
ReplyDeleteIs that an admission on your part, Steve?
Anonymous,
ReplyDelete"Any similar studies, or observations, on Mulatto/mixed-race sprinters from other parts of the world, ie - Africa, the Caribbean?"
None that I'm aware of. But I think it goes without saying that American and Caribbean blacks tend to be both more European-admixed and more competitive in sprinting than native West Africans (though for obvious reasons we shouldn't put undue weight on this fact).
Hail,
"Simply a lack of sufficient non-black matrilineal ancestry among Caribbean Blacks?"
Perhaps. Historic European admixture in Jamaicans is male-biased to an even greater degree than in the US; so if the Jamaican sprinters have more white admixture, we wouldn't necessarily expect it to show up in the mtDNA results. Or if the effect is entirely explainable by very recent admixture then obviously we would expect little in Jamaica.
Steve,
I do recall your statements to that effect. Even if elite US black sprinters (broadly-construed) are whiter than average US blacks, it's conceivable that at the very highest level, black sprinters tend to be very black. If that could be demonstrated, it would be interesting, and would go some way to proving a West African-specific genetic component to elite sprinting success. But for now, it has not been demonstrated.
You can see pictures of the last 9 world record setters in the men's 100m dash at http://sports.espn.go.com/oly/trackandfield/columns/story?columnist=fish_mike&id=4394250
ReplyDeleteI would say that at least six out of nine are significantly more African-looking than the average African-American.