In this project the investigators will take reproductive histories from men and women of an Indian society in Paraguay, in order to compare their demography with that of other hunter- gatherer (foraging) groups. The PI's hope to get data on the births and deaths in the past few years and access local records on births and deaths since 1971. They will also observe work patterns and social relationships among tribal members. The PI's will analyze the age-sex structure of the population, the causes and rates of mortality, women's fertility, men's fertility, and population growth rates. They will test hypotheses about reproductive tradeoffs among the tribesmen, including the role of food sharing, the age at first marriage for both sexes, the interbirth interval, the sex ratio of offspring, step-parenting, promiscuity and spouse-sharing. They will also analyse the causes and consequences of infanticide and homicide in the population. This research will contribute to the growing body of data on modern foraging peoples and is urgent because of the rapid disappearance of the foraging way of life. Only by collecting such data while it is still available can scientists construct and test models about the demographic parameters that characterized our ancestors until very recently.
