Polygyny and Fertility Among the Sereer of Senegal

The population laboratory of Ngayokhème, in Senegal, has been observed longitudinally since 1962. Information on marital status at the time of birth (rather than at the time of a survey) is used to examine the effect of polygyny on fertility. Although plural marriages are less fertile and the rank order of the wife has an effect, the mechanism appears to operate through the age difference of the spouses and the greater likelihood of temporary separate residence in the case of polygynous marriages. An examination of birth intervals suggests that the lower fecundity of older men, rather than a reduction of the frequency of intercourse, is the main factor. However, there is little relation between the fertility of different wives of the same polygynists.