>Eurasian populations have been "dense" from the perspective of disease transmission for only an eyeblink of Darwinian time.(posted 8758 days ago)I'm not sure this argument doesn't equivocate between "Darwinian time" in the sense of the time required for speciation, and the process of natural selection itself. Surely, for example, if you're in the half of the population which doesn't have the sickle-cell gene and there's a malaria epidemic going on, then "Darwinian time" is *right now*.
I actually find Diamond's argument quite a convincing explanation for the lack of genetic diversity in populations outside Africa -- that it is the result of regular removal of all non- resistant genes from the pool through epidemic, rather than through in-breeding from an originally small gene pool.
Although, of course, the conclusion that JD wishes to establish does seem a bit too politically convenient to be true. I don't see how there could be a gene for "general resistance to epidemic diseases" (the fact of evolution among germsn ought to see to this), and piecewise elimination of sections of the population by epidemics would be as likely to increase genetic intelligence as to decrease it. This would suggest that no amount of Darwinian time would be sufficient for differences in intelligence to predictably evolve as a result of exposure to infectious disease.
regards
dd Contributed by Daniel Davies (daniel.davies@flemings.com) on January 4, 2000.