Document Type



Four ethnically, cultural-historically and linguistically distinct subsets of the Sells Reservation Papago population are identified using ethnographic and demographic data. Breeding patterns of these four isolates are described and compared with fertility and mortality parameters. Isolates which experienced greater ethnic and isolate admixture were those less geographically remote from western influences and showed greater fertility than those more endogamous and geographically remote isolates. Overall population replacement rates of all the isolates, however, were similar. Several possible explanations for the observed fertility differentials are discussed and evaluated. It is argued that population-biological constraints on survival, high rates of emigration and adverse economic conditions require that fertility rates be appropriate within narrow limits for continued survival of the reservation population.