Tendencies in the Tempo of Prehistoric Agricultural Expansions

Abstract This paper reviews the data and some models of premodern farming expansions. Comparison of archaeological data and models makes it possible to estimate the relative importance of demic and cultural diffusion, as well as the number of hunter-gatherers that were incorporated in the populations of early farmers per farmer and generation. At continental and large scales, most inland spread rates around the world were about 1 km/year and driven mainly by demic diffusion. However, the 1 km/year general rate is an average, which is useful as a metric that can be contrasted with the regional variation to understand the processes that sped or slowed expansion. At regional scales, estimations of spread rates performed so far refer to the Neolithic in Europe and Anatolia, the areas from which more radiocarbon dates are available. Along the inland European route, early farmers found increasing densities of hunter-gatherers and the wave of advance slowed down. Competition for space explains this slowdown reasonably well. In contrast, along the western Mediterranean, the expansion was extremely fast and can be explained by very long dispersal distances, about 300 km per generation. Other factors such as non-isotropic dispersal, mountains, soils, climate, diseases, etc. could have also affected spread rates.