Evidence for genetic and behavioral adaptations in the ontogeny of prehistoric hunter-gatherer limb robusticity
Résumé
Biomechanical analyses of past populations have primarily focused on adults and interpreted variation in
limb bone robusticity as indicative of differences in behavior. However, prior to skeletal maturity large
changes occur in limb bone robusticity and shape. During ontogeny, the accrual of bone is regulated by
differences in genetics and nutrition as well as mechanical loading. We consider how long bone
robusticity changes from birth to young adulthood in order to understand when population differences
appear during development and why this occurs.
We analyzed the femoral and humeral midshafts of four prehistoric hunter-gatherer skeletal samples
from four regions: Cis-Baikal, Siberia, Point Hope, Alaska, the central Japanese coast, and the South African
Cape. Some statistically significant differences between populations manifest at birth or soon after.
Some of this systemic patterning likely reflects adaptation of body shape to climate. Later Stone Age
South Africans also appear to demonstrate low limb rigidity residuals as a result of growth towards a
unique body type. Differentiation between populations also increases with age, pointing to functional
adaptation as a result of behavioral differences. This proves largely concordant with other lines of evidence
for differing levels of terrestrial and aquatic mobility in these populations.