Abstract
The well known cline in ABO blood group gene frequencies in Japan was analysed based on the working hypothesis of a transient cline formed by the admixture of two heterogeneous populations by diffusion.Mathematically, the model corresponds to solving the diffusion equation with a step function as the initial condition. Using the A allele frequency data, the position of the initial discontinuity in the gene frequency is estimated by simulation as having been in the vicinity of present day Gifu City, and again assuming 20 km per generation of 25 years for a standard deviation of migratory distance the time as approximately 2, 000 years since the commencement of admixture. This and other results of simulation were discussed in the light of possible population movements induced by rice crop farming during the Yayoi era in western Japan.
