Long bone shaft robusticity and body proportions of the Saint-Cesaire-1 Chatelperronian Neanderthal

The Chatelperronian Saint-Cesaire 1 Neanderthal partial skeleton exhibits an overall morphology similar to earlier Neanderthals, but it is associated with an early Upper Palaeolithic technological complex. To assess whether its habitual mechanical loading patterns from manipulative and locomotor behaviour were more similar to those of Middle Palaeolithic or earlier Upper Palaeolithic humans, we compared its long bone shaft geometric properties to those of European Neanderthals and early modern humans. As appropriate, body proportions of Neanderthals and European early modern humans were employed to scale diaphyseal strength. Saint-Cesaire 1 is similar to Neanderthals in its rounded proximal femoral shaft, lack of a femoral pilaster and rounded tibial crests, but it contrasts with Neanderthals in its pronounced humeral deltoid tuberosity and dorsally projecting medial femoral buttress. In other diaphyseal cross-sections it is similar to members of both samples. In the lower limb, Saint-Cesaire 1 resembles both samples in robusticity when given Neanderthal proportions, but it appears hyper-robust when earlier Upper Palaeolithic human proportions are used. Its femoral midshaft exhibits the greater medio-lateral rigidity of the Neanderthals but resembles early modern humans in its elevated antero-posterior strength. The femoral diaphyseal shapes fit best with a model of Neanderthal pelvic and hip proportions, combined with an early modern human emphasis on antero-posterior loading of the femoral midshaft. In the upper limb, its cortical area distribution is closer to those of the Neanderthals, but its proximal diaphyseal shapes provide a mixed pattern. This Chatelperronian hominid therefore provides a mosaic in terms of diaphyseal loading patterns, but the load levels and patterns are reasonable for a Late Pleistocene human only if it is provided with the hyper-arctic body proportions of a Neanderthal.