MICROSATELLITE DIVERSITY AND THE DEMOGRAPHIC HISTORY OF MODERN HUMANS

Wt have examined differences in diversity at 68 microsatellite loci am ong human population samples from three major continental groups to ev aluate the hypothesis of greater African diversity in this rapidly evo lving class of loci, Application of a statistical test that assumes eq ual mutation rates at all loci fails to demonstrate differences in mic rosatellite diversity, while a randomization test that does not make t his assumption finds that Africans have significantly greater microsat ellite diversity (P < 10(-8)) than do Asians and Europeans. Greater Af rican diversity is most apparent at loci with smaller overall variance in allele size, suggesting that the record of population history has been erased at repeat loci with higher mutation rates. A power analysi s shows that only 35-40 microsatellites are needed to establish this d ifference statistically, demonstrating the considerable evolutionary i nformation contained in these systems. On average, African populations have approximate to 20% greater microsatellite diversity than do Asia n and European populations. A comparison of continental diversity diff erences in microsatellites and mtDNA sequences suggests earlier demogr aphic expansion of the ancestors of Africans.