Schematic representation of the two grids of demes representing South-Western Europe (SWE) and North-Western Africa (NWA). The whole simulated area is subdivided into 256 demes. The two crosses represent the demes where the settlement of the areas starts from a common genetic pool t generations ago. There are two different migration rates: m
is the migration rate between demes within a continent (either SWE or NWA) and m
is the migration rate between demes among continents. Continents are connected by 8 demes on each side.