Temporal changes in mobility and sexual division of labor in Holocene South Australians: An analysis of external bone metrics in the Roonka Flat sample

The Roonka Flat skeletal sample is an important contribution to our understanding of biological and behavioral adaptations in South Australians during the Holocene. The development of the El Niño Southern Oscillation (ENSO) ~ 4 kya caused significant changes in climate, vegetation, and faunal assemblages between the early Holocene and the late Holocene. A transition from wetter and warmer conditions pre-ENSO to cooler and dryer climate post-ENSO would have had an impact on human populations inhabiting South Australia. In fact, archaeological deposits across the continent denote a change toward a lighter, more flexible tool kit and a more diverse diet at the onset of the post-ENSO period. Further, present archaeological evidence supports predictions made by optimal foraging theory that South Australian Aboriginals became more mobile and demonstrated more marked sexual division of labor after the onset of ENSO.The purpose of this study is to use the framework of bone functional adaptation to test these predictions by examining changes in long bone diaphyseal metrics between pre-ENSO and post-ENSO skeletons from the Roonka Flat sample. If people became more mobile post-ENSO, then they should exhibit more ovular femoral and tibial diaphyses; and if they had marked sexual division of labor, then males and females should demonstrate differing patterns of upper limb bilateral asymmetry in the humerus, radius, and ulna. Results from the femur, humerus, and ulna support these predictions. The whole population becomes more mobile post-ENSO to better exploit less productive patches by expanding their foraging radii. This change toward increased mobility is more notable in females. Further, males and females demonstrate sexual division of labor withmales exhibiting a notable right-side bias reflecting the use of hunting implements such as spears, while females have relative symmetry between the right and left sides perhaps due to the increased use of technologies like grindstones and digging sticks used to gather and process high handling-cost foods.