The age of a mutant gene was studied under various cases of population size fluctuation. A Monte Carlo method was used to simulate a branching process under the assumption that the probability distribution of descendant gene numbers follows a Poisson distribution. It is shown that a population with a constant population size tend to have larger age of a mutant gene than populations in which the size is fluctuating. It was also shown that for a Negrito population of Luzon Island, the observed distribu tion of gene transmission estimated through pedigree data agrees well with a Poisson distribution.
The Anthropological Society of Nippon