Demographic characteristics and their genetic implications in a small island

Abstract

SummaryThe family registration records from a village population in a small island of Japan are used to assess the effect of demographic differentiation within a population on genetic measures. When the couples studied are classified by birth cohorts and origins, wives of the couples where one spouse came from elsewhere were older at marriage and had a shorter duration of marriage or registration than wives where both spouses were natives of the village. The mean number of offspring is statistically smaller in the former except for the latest cohort, due mainly to out-migration during the reproductive ages which also resulted in low rates of marriage among the offspring within the village. This leads to a small effective population size and an increased likelihood of genetic drift in the overall population.