Comments on: Africa's genetic diversity revealed by full genomes of a Bushman and a Tutu

By: Ethnic diversity 'breeds mistrust'

Ethnic diversity 'breeds mistrust' — Fri, 19 Nov 2010 17:19:01 +0000

[...] their genomes and you’d see more variety than you would between a European and an Asian. Africa’s genetic diversity revealed by full genomes of a Bushman and a Tutu | Not Exactly Rock… In a nutshell, this is an argument that could be used to say that races do not exist. After all, [...]

By: Trond Engen

Trond Engen — Sat, 20 Feb 2010 01:17:09 +0000

It’s a large, large language family, easily comparable to Indo-European at the very least.

If at all. Isn’t it more of a convenient cultural/geographical lumping?

By: DrYak

DrYak — Thu, 18 Feb 2010 22:19:49 +0000

I think that you will find that Archbishop Tutu is of Twsana, not “Twsama” origen.
I also question “scientist’s” description of “Africa” having a mild climate. Africa is a very large continent with a huge variety of climatic zones. Even just in Southern Africa you have the mediterranian climate of the southern Cape, the tropical climate of northern Kwazulu-Natal and Mozambique, the velt of the central plateau and the extreme desert of the Namib. It is also subjected to periodic drought conditions that have waxed and waned based on oceanic and climate cycles. I can assure you that the Kalahari where the majority of the San peoples live is in no way a mild climate. Extremely hot with very scarce water and major fluctuations of food availability based on animal migrations and a growing season based on the very seasonal rains. I agree with the authors of the study that the genetic diversity is primarily based on the age and ancestral nature of the populations rather than relaxed selection pressure. Having spent a considerable amount of time out in the Southern African bush including the kalahari I challenge anyone who things that the climate and selection pressure are “mild” to live like the San peoples do for a month…

By: travc

travc — Thu, 18 Feb 2010 21:39:32 +0000

One interesting implication (not quite enough data for a result, yet) is that this group has managed to avoid inbreeding.
It seems pretty common to assume aboriginal groups (especially when they have small populations today) were somehow always isolated. Logically, that should be the exception, not the rule, since inbreeding isn’t exactly a good thing for the long term success of a population. Yeah, the exceptions are cool simplified cases we can make more interesting conclusions about, but again, not the rule.
Maybe we still have too many geneticists trained on lab strains.
Also, as I mentioned elsewhere, these results seem to be exactly what we should expect for a species which has undergone a recent radiation. We’ve seen the same sort of thing numerous times in other clades.

By: scientist

scientist — Thu, 18 Feb 2010 03:35:59 +0000

With regard to African athletic performance, the prevalence of myostatin mutations ranges from ten to twenty percent in Africa, while only 1% in Europe and Asia. As well the slavers culled for heavily muscled slaves because they fetched a better price and were more likely to survive the arduous journey bound and shackled, stacked like cordwood in the hold of a ship.

By: Scientist

Scientist — Thu, 18 Feb 2010 03:28:41 +0000

Genetic diversity increases where there is low selection pressure. Africa has a mild climate without seasonal food scarcity. It is also true that the founder effect decreases genetic diversity the farther a population migrates from their origins.

By: Henry Harpending

Henry Harpending — Thu, 18 Feb 2010 00:18:44 +0000

What does it mean for a SNP to ‘match’ since a SNP is a locus at which there is variation. Presumably one allele or the other is ancestral at every SNP.
The ‘old lineage’ stuff doesn’t quite seem sensible either. Pick an allele at a locus from me, an allele from the same locus from a Bushman, follow them back to their common ancestor. The length of the two branches, hence the probability of a mutation have happened is exactly the same on each branch. Hence the probability of the ancestral state (or the expected frequency of the ancestral state if we extend the sample of size 2 to larger samples)is exactly the same in both of us. Alan Rogers recently published a nice paper showing this in greater detail.

By: Ed Yong

Ed Yong — Wed, 17 Feb 2010 23:57:34 +0000

Aw hell. You can tell I wrote this in a rush, can’t you? Fixed the “Bushman language” thing and Watson’s nationality. Thanks to everyone for the constructive feedback.

By: zackoz

zackoz — Wed, 17 Feb 2010 23:53:59 +0000

James Watson is British?

By: JBC

JBC — Wed, 17 Feb 2010 22:23:24 +0000

Not only have chimps obviously evolved somewhat since our divergence with the last common ancestor (although not nearly enough to account for only 6% similarity! Even 87% is a bit low…) but the state of the chimp genome within the databases is a bit miserable. The assembly is simply wrong in some places.