Linking structural variability in long bone diaphyses to habitual behaviors: Foragers from the southern African Later Stone Age and the Andaman Islands

The cross-sectional distribution of cortical bone in long bone diaphyses is highly responsive to mechanical loading during life, yet the relationship between systemic and localized influences on skeletal structure remains unc lear. This study investigates postcranial robustness throughout the body am ong adults from two groups of foragers with different patterns and modes of mobility, to determine whether there is evidence for upper vs. lower body localization of skeletal robustness. The samples used for this comparison a re from the southern African Later Stone Age (LSA; n = 65, male = 33, femal e = 28) dating from ca. 10,000 to 2,000 B.P., and 19th century indigenous A ndaman Islanders (AI; n = 36, male = 17, female = 16). The LSA were highly mobile foragers who did not exploit offshore marine resources. In contrast, the AI had tightly constrained terrestrial, but significant marine, mobili ty. Geometric properties of cortical bone distribution in the diaphyses of the clavicle, humerus, femur, tibia, and first metatarsal are compared betw een the samples, providing a representation of skeletal robustness througho ut the body. Multivariate ANOVA shows the AI to have significantly stronger clavicles and humeri, while the LSA femora, tibiae, and first metatarsals are stronger than those of the AI. These patterns, in which upper and lower limbs show biomechanical properties that are consistent with habitual beha viors, suggest localized osteogenic response. Although postcranial robustne ss appears to be correlated with overall limb function, the results suggest that more proximal elements within the limb may be more responsive to mech anical loading. (C) 2001 Wiley-Liss, Inc.