1Anthropology, University of Massachusetts, 2Center for Functional Anatomy and Evolution, Johns Hopkins University, 3Archaeology, University of Oulu, Finland, 4Anthropology and Human Genetics, Charles University, Czech Republic, 5Anthropology, Natural History Museum, Vienna.
Thursday Afternoon, Forum Suite
The postcranial skeleton of contemporary humans exhibits significantly reduced robusticity compared to Late Paleolithic ancestors. Little is known, however, of this gracilization process over the intervening period. We analyzed measures of long bone (femur, tibia, humeri) robusticity and shape for 2170 skeletons distributed broadly across Europe and ranging from 30,000 BP to 1900s. Polar modulus (Zp) and ratios of anteroposterior (AP) and mediolateral (ML) bending moments were used as estimates of diaphyseal rigidity and shape, respectively.
Lower limb robusticity decreases significantly for both sexes until around 2,000 BP, with small but significant increases in Medievals, followed by further declines into modern times. Tibia and femora become increasingly circular in cross-section until 5,000 BP, with little ulterior change. Upper limb robusticity, however, follows more complex trajectories. Male humeral robusticity fluctuates substantially, significantly decreasing between 30,000 and 2,000 BP, increasing again in Medievals, with little net change over the entire period. Females, however, show sharp robusticity declines, particularly after the Neolithic. Humeral shape for both sexes becomes increasingly more circular in post-Paleolithic groups.
The combination of reduced lower limb robusticity, albeit with some fluctuation (increases in Medievals), with increased circularity, suggests that, while physical activity levels remained high in some periods, this activity did not engender the high AP bending moments associated with elevated mobility. Similarly, the increase circularity characterizing the upper limb of post-Paleolithic groups probably reflects reduced use of technologies placing high AP bending stresses on the humerus. Results focusing on regional and finer temporal differences will also be discussed.
This study was funded by NSF grant number 1124775 and NSF grant number 0642297.