and, incidently, sex. from The Ancestor’s Tale — h/t to the person who linked to this on twitter the other evening. i forgot who it was! (*^_^*) (sorry!) [pgs. 406-408 — links added by me]:
“It is genuinely true that, if you measure the total variation in the human species and then partition it into a between-race component and a within-race component, the between-race component is a very small fraction of the total. Most of the variation among humans can be found within races as well as between them. Only a small admixture of extra variation distinguishes races from each other. That is all correct. What is not correct is the inference that race is therefore a meaningless concept. This point has been clearly made by the distinguished Cambridge geneticist A. W. F. Edwards in a recent paper called ‘Human genetic diversity: Lewontin’s fallacy’. R. C. Lewontin is an equally distinguished Cambridge (Mass.) geneticist, known for the strength of his political convictions and his weakness for dragging them into science at every possible opportunity. Lewontin’s view of race has become near-universal orthodoxy in scientific circles. He wrote, in a famous paper of 1972:
“‘It is clear that our perception of relatively large differences between human races and subgroups, as compared to the variation within these groups, is indeed a biased perception and that, based on randomly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals.’
“This is, of course, exactly the point I accepted above, not surprisingly since what I wrote was largely based on Lewontin. But see how Lewontin goes on:
“‘Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.’
“We can all happily aggree that human racial classification is of no social value and is positively destructive of social and human relations. That is one reason why I object to ticking boxes in forms and why I object to positive discrimination in job selection. But that doesn’t mean that race is of ‘virutally no genetic or taxonomic significance’. This is Edwards’s point, and he reasons as follows. However small the racial partition of the total variation may be, if such racial characteristics as there are are highly correlated with other racial characteristics, they are by definition informative, and therefore of taxonomic significance.
“Informative mean something quite precise. An informative statement is one that tells you something you didn’t know before. The information content of a statement is measured as reduction in prior uncertainly. Reduction in prior uncertainty, in turn, is measured as a change in probabilities…. If I tell you Evelyn is male, you immediately know a whole lot of things about him. Your prior uncertainty about the shape of his genitals is reduced (though not obliterated). You now know facts you didn’t know before about his chromosomes, his hormones and other aspects of his biochemistry, and there is a quantitative reduction in your prior uncertainty about the depth of his voice, and the distribution of his facial hair and of his body fat and musculature….
“Now to the question of race. What if I tell you Suzy is Chinese, how much is your prior uncertainty reduced? You now are pretty certain that her hair is straight and black (or was black), that her eyes have an epicanthic fold, and one or two other things about her. If I tell you Colin is ‘black’ this does not, as we have seen, tell you he is black. [he might be mixed race.-h.chick] Nevertheless, it is clearly not uninformative. The high inter-observer correlation suggests that there is a constellation of characteristics that most people recognise, such that the statement ‘Colin is black’ really does reduce prior uncertaintly about Colin. It works the other way around to some extent. If I tell you Carl is an Olympic sprinting champion, your prior uncertainty about his ‘race’ is, as a matter of statistical fact, reduced. Indeed, you can have a fairly confident bet that he is ‘black’.”
of course, don’t forget: there’s more to human biodiversity than just racial differences! see: most of this blog.
see also: Human Genetic Diversity: Lewontin’s Fallacy @wikipedia.
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