Selective female infanticide by the Dene hunting tribes of Subarctic Canada is noted in the historical and ethnographic record. Unusually extensive and complete census data on two generations of Mackenzie Dene in the infanticide era manifest male-skewed sex ratios that suggest that the number of females in those generations was reduced through infanticide by 20 percent or more. These and later census data falsify the assumption of depopulation of the Mackenzie Dene by exogenous disease in the historic era, rendering invalid the depopulation theory on which arguments for the "loss" of putative aboriginal unilocal-unilineal organization have been based. Diagrammatic population models are employed to explore the capacity of the population to sustain mortality from introduced diseases when counterbalanced by the elimination of selective female infanticide as a mortality factor.