Scales and units of analysisOver the past forty years, a fascinating dialogue has been developing between archaeology and genetics, specifically in relation to the question of the dispersal of domesticated plants and animals into Europe and its relationship with the movements of human populations. This debate has often been marked by a degree of mutual confusion, owing largely to the different temporal and spatial scales at which the two disciplines operate, and the different questions that they address (Brown and Pluciennik 2001. 101). While genetics generally concerns itself with the global or continental scale, archaeology is often more focused on the regional and the local, with the result that phenomena that are described at different levels of magnitude may appear to contradict each other. Some common ground is now beginning to emerge, but from an archaeological point of view it is especially interesting to ask whether the finegrained patterns that we think we can discern in the evidence can be accommodated by the broader sweep of the genetic information, or whether there is a degree of dissonance between the two, whose investigation might prove fruitful.We are indebted to Albert Ammerman and Luca Cavalli-Sforza (1971;1973) for initially stimulating debate with their discussion of the expansion of agriculture into Europe through demic diffusion, developed in the first instance in relation to radiocarbon dates from Neolithic sites, and later used as a means of explaining the distribution of genetic markers across the continent. The model of farming communities gradually expanding as their population rose, fuelled by the productivity and reliability of their subsistence base was explicitly differentiated from migrationary arguments, in which communi-