A new model for calculating the lumbar lordosis angle in early hominids and in the spine of the Neanderthal from Kebara

The debate over the posture of early hominids is longstanding, perhaps because the absence of a reliable method for reconstructing the lumbar lordosis angle (LA) in early hominid spines has made it difficult to determine whether their posture resembled or differed from that of modern humans. We have developed a new model for predicting the lordotic curvature of the lumbar spine of early hominids based on the relationship between the lordotic curvature and the orientation of the articular processes in the lumbar spines of living primates (modern humans and nonhuman primates). The orientation of the inferior articular processes explains 89% of the variation in lordotic curvature among living primates and, thus, should be a reliable predictor of the lumbar LA in disarticulated hominid spines. Based on this model, we calculated a LA of 25-26 degree angle for the Kebara 2 Neanderthal. The calculated value for Kebara 2 is below the normal range of lordosis for modern humans (30-79 degree angle).