The wave-of-advance model is applied to the uptake of an advantageous technology through a population, such as the arrival of neolithic farmers in Europe, the domestication of the horse, the wheel, iron tools, political organisation or advanced weaponry. Any trait which preexists alongside the advantageous one could be carried along with it, such as genetics or language, regardless of any intrinsic superiority. Decoupling of the advantageous trait from other ''hitchhiking'' traits depends on its adoption by the preexisting population. Here we adopt a wave-of-advance model based on food production on a heterogenous landscape (Europe, India, South Africa) with multiple populations. Two key new results arise from geographic inhomogeneity: the ''subsistence boundary'' - land so poor that the wave of advance is halted, and the temporary ''diffusion boundary'' where the wave cannot move into poorer areas until its gradient becomes sufficiently large. At diffusion boundaries, farming technology may pass to indigenous people already in those poorer lands, allowing their population to grow and resist encroachment by farmers. Ultimately, this leads to the halt in spread of the ''hitchhiking'' trait and establishment of a permanent ''cultural boundary'' between distinct cultures with equivalent technology.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..