Population variation in second metacarpal sexual size dimorphism.

Abstract

This paper contrasts levels of sexual size dimorphism in second metacarpal osteometric and geometric morphology in two bioculturally distinctive populations: 19th century Euro-Canadian settlers, and proto/historic central Canadian Inuit. Significant within-group sexual size dimorphism is found for all variables, though few show significant interpopulation differences. However, in every case the Euro-Canadian sample is more dimorphic than the Inuit sample. Notably, differences reside in geometric measures (total area, Imax) sensitive to variation in functional strain, and thus are interpretable in light of proximate causal models, i.e., activity profiles distinct from generalized mode of subsistence. Other proximate factors, such as nutritional stress acting to diminish Inuit sexual size dimorphism, may also play a role. However, models often cited to explain dimorphism, such as marriage practice (e.g., polygyny) or division of labor situated in mode of subsistence, do not. The higher sexual size dimorphism in the 19th century settler sample belies the notion that technological progress inevitably leads to reduced dimorphism.