What clues does pregnancy provide toward our evolution?
Hominin females have evolved with lumbar morphology that allows them to “self-select” a more curved spinal posture. Morphological differences were previously hypothesized to mechanically balance the trunk about the hip while carrying a ventral abdominal load (fetus during pregnancy) by allowing for repositioning of the center of mass over the hip joints through pregnancy. This support hypothesis implicates that the driving force behind female lumbopelvic morphology is gravitational vertical forces, which has distinct implications for the evolution of hominin bipedalism. Based on the support hypothesis, we would expect all pregnant women to choose a more curved spinal posture since every human pregnancy involves trunk mass growing anteriorly to the hip joints. Instead, there are reports indicating that the range of self-selecting a lumbopelvic posture during pregnancy is not consistently toward more curvature. Findings from this study will help us understand the evolution of H. sapiens sexual dimorphisms.
- Catena RD, WC Wolcott (2021). Self-selection of gestational lumbopelvic posture and bipedal evolution. Gait and Posture. 89:7-13.