Bipedalism and musculoskeletal stress markers: Variation and what it reveals about adaptation, environmental stress, and reconstructing activity patterns

Abstract

Understanding the origins of bipedalism has been an important part of anthropological research. Many traits have been used to determine bipedalism, but musculoskeletal stress markers (MSMs) have not received much attention by paleoanthropologists. MSMs are observable locations on bone where muscles, tendons, or ligaments attach. Bioarchaeologists use MSMs to reconstruct activities. Using MSMs, anthropologists have addressed issues regarding differences in activity patterns (within and between populations) related to subsistence patterns, sex differences in specific activities, and the effects of terrain types. However, age and body weight are confounding factors of MSMs. Regardless of activity, it seems that older and larger individuals have greater MSM scores than younger and smaller individuals. Since these two factors are difficult to control for in the fossil record, paleoanthropologists may be reluctant to use MSMs to determine bipedalism. This chapter looks at the evidence of nonhuman primate research and modern human variation to deduce whether MSMs on fossils can be successfully analyzed to aid in understanding the evolution of bipedalism.