Patterns of Sexual Dimorphism in North American Indian Groups

This study examines patterns of sexual dimorphism in 26 North American Indian and Siberian groups. Past research on sexual dimorphism has looked into possible causative factors such as nutritional status, settlement type, marriage systems, sexual division of labor, and climate. No one explanation can be universally applied to all populations. Three measurements of height; standing height, sitting height, and sub-ischial height were examined for variation in sexual dimorphism. Univariate and multivariate statistical tests were performed to determine which component of stature contributes more to the variability in sexual dimorphism.

Results of this study indicate that the groups of the Northwest coast and Siberia both exhibited a pattern of low sexual dimorphism relative to the inland North American groups. It is suggested that a more recent ancestry between the Northwest coast and Siberian groups is partly responsible for a similar pattern of dimorphism. Further, it is suggested that a long-standing adaptation to a cold climate in Siberia is evidenced in the low dimorphism of the Northwest coast and Siberian groups. Leg length contributed more to group variability, but it is known that leg length is more susceptible to environmental changes. This study suggests that the differences in sexual dimorphism patterns in North America and the similarities in patterning of the Northwest Coast groups and Siberian groups are a reflection of the involvement of a combination of genetic and environmental factors.