Genetic demography of the amazonian Ticuna Indians

The Ticuna Indians of Brazil are now a largely acculturated and integrated tribe, situated for the most part in villages along the Solimões river. Demographic information collected in eight of their villages is reported here. For five of them detailed data concerning migration, fertility and mortality were obtained. They are characterized by a relatively large mobility, high fertility (mean number of livebirths per female of age 40 or more: seven), low (2·5%) frequency of sterile couples, and relatively low mortality for groups living at this cultural stage (25% of deaths before the age of reproduction). This low mortality, and a relatively small variance in the number of live-born children in completed families, lead to the lowest index of opportunity for selection obtained thus far in populations of South American Indians (0·54).