Genetics and Africa

[Guest guest]

Mel wrote:

<The interesting point also arises as to why " West Africans " excel in

these specific running events, but their genetically related cousins

from adjacent or distant parts of Africa do not. ..... >

This is not a good criticism against Entine's arguments. If I

recall, he mentions Kidd's work in a few of his articles.

[Note that Entine in one breath compiles lists of what he considers to be

" West African " athletes (without as much as a single reference as to the

genetic proof thereof) and in the next breath reiterates what Kidd has stated

about

the huge degree of variation in Africa. His implications about some form of

racial purity are questionable and the lumping together of so many West African

tribes, when he acknowledges that there is huge variety of race in all parts

of Africa. I will find his arguments more compelling when genuine genetic

and kinathropometric profiles are constructed for all of those athletes whom he

classifies as " West African " (note that he even classifies several

" Afro-Americans "

in this class, but he knows not a whit about their exact heritage). He has

embroided such a crafty tapestry of genuine science and opinion that many

people cannot easily distinguish between correlation, causation and association.

As I wrote before, this is precisely what von Daniken and Hancock have done in

their literary best-selling theories about man coming from outer space. Entine

is to racial superiority what Hancock is to pyramidology. Fascinating theory,

a jolly good, well referenced read, but very thin on definite proof! Mel Siff]

For those not familiar, Kidd's work suggests that in general, there

is more genetic diversity in africa than the rest of the world's

populations. Some have used Kidd's research (wrongly or rightly)

to argue that it may explain the high number of elite athletes that

have African heritage. I'm kinda skeptical of this argument but

here is one version of it:

" Kidd and his colleagues have been taking DNA samples from two

African Pygmy tribes in Zaire and the Central African Republic and

comparing them with DNA samples taken from populations all over the

world. What they have been looking for is variants-subtle differences

between the DNA of one person and another-and what they have found is

fascinating. " I would say, without a doubt, that in almost any single

African population-a tribe or however you want to define it-there is

more genetic variation than in all the rest of the world put

together, " Kidd told me. In a sample of fifty Pygmies, for example,

you might find nine variants in one stretch of DNA. In a sample of

hundreds of people from around the rest of the world, you might find

only a total of six variants in that same stretch of DNA-and probably

every one of those six variants would also be found in the Pygmies.

If everyone in the world was wiped out except Africans, in other

words, almost all the human genetic diversity would be preserved…

There is nothing particularly scary about this fact, and certainly

nothing to warrant the kind of gag order on talk of racial

differences which is now in place. What it means is that comparing

élite athletes of different races tells you very little about the

races themselves. A few years ago, for example, a prominent scientist

argued for black athletic supremacy by pointing out that there had

never been a white Jordan. True. But, as the Yale

anthropologist Marks has noted, until recently there was no

black Jordan, either. Jordan, like Tiger Woods or

Wayne Gretzky or Cal Ripken, is one of the best players in his sport

not because he's like the other members of his own ethnic group but

precisely because he's not like them-or like anyone else, for that

matter. Élite athletes are élite athletes because, in some

sense, they are on the fringes of genetic variability. As it happens,

African populations seem to create more of these genetic outliers

than white populations do, and this is what underpins the claim that

blacks are better athletes than whites. But that's all the claim

amounts to. It doesn't say anything at all about the rest of us, of

all races, muddling around in the genetic middle.

http://www.gladwell.com/1997/1997_05_19_a_sports.htm

Some references on Kidd's work:

http://info.med.yale.edu/genetics/kkidd/point.html

http://www.rps.psu.edu/0101/africa.html

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Gene 1997 Dec 31;205(1-2):161-71

Nuclear DNA diversity in worldwide distributed human populations.

Zietkiewicz E, Yotova V, Jarnik M, Korab-Laskowska M, Kidd KK,

Modiano D, Scozzari R, Stoneking M, Tishkoff S, Batzer M, Labuda D.

Nucleotide variation was examined in an 8 kb intronic DNA bordering

exon 44 of the human dystrophin gene on Xp21. Thirty-six

polymorphisms (substitutions, small insertions/deletions and one (T)n

microsatellite) were found using SSCP/heteroduplex analysis of DNA

samples from mixed Europeans, Papua New Guineans as well as from six

African, three Asian and two Amerindian populations. In this way the

European bias in the nuclear polymorphism ascertainment has been

avoided. In a maximum likelihood tree constructed from the frequency

data, Africans clustered separately from the non-African populations.

Fifteen polymorphisms were shared among most of the populations

compared, whereas 13 sites were found to be endemic to Africans and

four to non-Africans. The common sites contributed most to the

average heterozygosity (Hn=0.101%+/-0.023), whereas the endemic ones,

being rare, had little effect on this estimate. The F(ST) values were

lower for Africans (0.072) than for non-Africans (0.158), suggesting

a higher level of gene exchange within Africa, corroborating the

observation of a greater number of segregating sites on this

continent than elsewhere. The data suggest a recent common origin of

the African and non-African populations, where a greater geographical

isolation of the latter resulted in a smaller number of newly

acquired polymorphisms.

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Nat Genet 1996 Jun;13(2):154-60

Minisatellite diversity supports a recent African origin for modern

humans.

Armour JA, Anttinen T, May CA, Vega EE, Sajantila A, Kidd JR, Kidd

KK, Bertranpetit J, Paabo S, s AJ.

Department of Genetics, University of Leicester, UK.

In a study of human diversity at a highly variable locus, we have

mapped the internal structures of tandem-repetitive alleles from

different populations at the minisatellite MS205 (D16S309). The

results give an unusually detailed view of the different allelic

structures represented on modern human chromosomes, and of the

ancestral relationships between them. There was a clear difference in

allelic diversity between African and non-African populations. A

restricted set of allele families was found in non-African

populations, and formed a subset of the much greater diversity seen

on African chromosomes. The data strongly support a recent African

origin for modern human diversity at this locus.

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Gus Karageorgos

Toronto, Canada