A sharp eyed reader, Stuart Ritchie, who on forensic examination will be revealed as a member of the Deary gang, has drawn my attention to a paper entitled: “Genetic Similarities Within and Between Human Populations” by D. J. Witherspoon, S. Wooding, A. R. Rogers,E. E. Marchani, W. S. Watkins, M. A. Batzer and L. B. Jorde
(2007) Genetics Society of America. DOI: 10.1534/genetics.106.067355 http://www.genetics.org/content/176/1/351.full.pdf+html
This paper shows that the debate about “variation within races is bigger than variation between races” depends largely on the number of loci being analysed, and the assumptions being made about the significance of the revealed differences. They concentrate “on the frequency, v, with which a pair of random individuals from two different populations is genetically more similar than a pair of individuals randomly selected from any single population. We compare v to the error rates of several classification methods, using data sets that vary in number of loci, average allele frequency, populations sampled, and polymorphism ascertainment strategy. We demonstrate that classification methods achieve higher discriminatory power
than v because of their use of aggregate properties of populations. The number of loci analyzed is the most critical variable: with 100 polymorphisms, accurate classification is possible, but v remains sizable, even when using populations as distinct as sub-Saharan Africans and Europeans. Phenotypes controlled by
a dozen or fewer loci can therefore be expected to show substantial overlap between human populations. This provides empirical justification for caution when using population labels in biomedical settings, with broad implications for personalized medicine, pharmacogenetics, and the meaning of race.
I have abstracted the key distribution shown above. It seems to me a balanced presentation of the issue, and the heated debate may revolve round “it depends what you mean about race” as well as “it depends how good your data are when carrying out a discriminant function analysis”.
have you seen this study you might find it interesting. tons of differentiation in some brain related genes, much higher than genes for skin color. these are just some genes we know the purpose of so far. so brain differentiation definitely exists in some capacity it's just a matter of knowing which traits
ReplyDeletehttp://www.biomedcentral.com/1471-2148/11/16
http://www.biomedcentral.com/content/figures/1471-2148-11-16-1.gif
thanks, an interesting study, and very relevant to this debate.
DeleteIs this v-measure used to decide taxonomical questions in other species?
ReplyDeleteI do not know, yet the measure is a logical one. By the way, the author used lowercase omega, and Live Writer transcribed it as v.
Deletehttp://westhunt.wordpress.com/2012/01/26/lewontins-argument/
ReplyDeleteThis argument is so profoundly ignorant that you would have to do away with the concept of species if you were to take it seriously:
"there is less mtDNA difference between dogs, wolves and coyotes than there is between the various ethnic groups of human beings, which are recognized as belonging to a single species."
The only person I know of which has made a convincing argument against the classic concept of race is the social psychologist Jonathan Haidt. He made the point that since evolution has accelerated so greatly over the last 40k years (Hawks et al: http://www.pnas.org/content/104/52/20753.abstract) there can be significant differences between adjacent populations and hence which continent group (i.e. traditional definition of race) you belong to might not be that informative. I find the argument persuasive.
I don't think that continent of origin, however traditional, is strictly enough. All than is required is a strong barrier to inter-marriage, which could include a major geographical feature or even a very strong religious or cultural divide. European Jews can be distinguished genetically from other Euroeans, despite their many generations together in the same continent.
DeleteI always encourage people to think about how much difference can be found among siblings, much less cousins.
ReplyDeleteA good point. I will have to think about that, and the various ways of making the point. (I will probably have to read back over several of your posts). Another general approach is to look at all genetic group differences in term of cousin distance, first and second cousins being pretty well related, down to seventh cousins which applies to just about anybody, if I understand the maths correctly.
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