INDO-EUROPEAN ORIGINS - A COMPUTER-SIMULATION TEST OF 5 HYPOTHESES

Allele frequency distributions were generated by computer simulation o f five models of microevolution in European populations. Genetic dista nces calculated from these distributions were compared with observed g enetic distances among Indo-European speakers. The simulated models di ffer in complexity, but all incorporate random genetic drift and short -range gene flow (isolation by distance). The best correlations betwee n observed and simulated data were obtained for two models where dispe rsal of Neolithic farmers from the Near East depends only on populatio n growth. More complex models, where the timing of the farmers' expans ion is constrained by archaeological time data, fail to account for a larger fraction of the observed genetic variation; this is also the ca se for a model including late Neolithic migrations from the Pontic ste ppes. The genetic structure of current populations speaking Indo-Europ ean languages seems therefore to largely reflect a Neolithic expansion . This is consistent with the hypothesis of a parallel spread of farmi ng technologies and a proto-Indo-European language in the Neolithic. A llele-frequency gradients among Indo-European speakers may be due eith er to incomplete admixture between dispersing farmers, who presumably spoke proto-Indo-European, and pre-existing hunters and gatherers (as in the traditional demic diffusion hypothesis), or to founder effects during the farmers' dispersal. By contrast, successive migrational wav es from the East, if any, do not seem to have had genetic consequences detectable by the present comparison of observed and simulated allele frequencies. (C) 1995 Wiley-Liss, Inc.