The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Fluctuating and Directional Asymmetry: skeletal evidence for life history theory and human evolutionary ecological variation in an archaeological South Dakota Arikara population


Anthropology, Northwestern University

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The majority of human infant long bones are physically symmetrical at birth with factors such as use preference, malnutrition, and disease contributing to asymmetrical growth during development. The present research uses life history theory and evolutionary ecology to explore fluctuating and directional asymmetry in South Dakota Arikara skeletal remains (700-1862CE).

Right and left maximum lengths of the humerus, radius, femur, and tibia were recorded for 308 individuals. Data were separated by age range and sex in order to analyze whether skeletal asymmetry changes over development and whether adult males and females are equally asymmetrical. Comparison with an archaeological New Mexico Ancestral Puebloan sample (n=198) was also performed in order to assess differing cultural impact on asymmetry.

Our results contribute to and reaffirm previous research showing that infants are predominantly symmetrical. In turn, children exhibit fluctuating asymmetry while adolescents and adults exhibit directional asymmetry. Among the adults sampled, females are more asymmetric than males in humeri and radii (p= 0.209; p= 0.189) while males are significantly more asymmetric than females in femora and tibiae (p= 0.023; p=0.048). Adult male and female Arikara exhibit significantly more asymmetric humeri than their same-sex Ancestral Puebloan counterparts (p=0.000; p=0.002). As a whole, this research presents asymmetry as a single biological manifestation resulting from cultural activities and environmental stressors on an archaeological population.

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