Femoral neck-shaft angle and climate: Preliminary report on a global study

Variation in the angle of the femoral neck relative to the shaft (the collodiaphyseal or neck-shaft angle, or NSA) is the subject of ongoing debate as to whether differences between modern (Holocene) human groups as well as among Pleistocene hominins reflect climatic adaptation (in relation to body shape) or habitual activity patterns (as a reflection, for instance, of forager, agricultural, or urban lifestyles). Among late Pleistocene hominins, the lower NSA of Neanderthals, for example, has been interpreted as a corollary of their more stocky, cold-adapted body build and, alternatively, as an outcome of a more physically demanding lifestyle. Among modern humans, average NSA varies markedly between groups in different regions. Recent studies have explored variation in NSA in relation to climate, but interpretation of results has been limited by measurement issues, generally small sample sizes, and the use of weak climatic proxies (such as latitude). This chapter reviews measurement problems and sources of error, and reports findings based on extensive sampling of more than 8,000 femora from over 80 countries. Variation in average NSA is examined in relation to meteorological indices (including mean annual and seasonal temperatures). Results indicate that while climatic factors are implicated in inter-group and regional variation, additional factors such as cultural buffering from the environment – especially regular use of thermally-effective clothing (which alters the microenvironment of the body) – need to be considered before drawing conclusions.