Insights into Neanderthal development, childbirth, and locomotion from the Palomas and Dederiyeh pelves.

The human pelvis reflects evolutionary compromises among childbirth, bipedal locomotion, and other factors such as pelvic floor stability and thermoregulation. However, limited fossil evidence has hindered understanding of how these factors shaped pelvic morphology in Neanderthals, our closest extinct relatives. Here, we present new virtual reconstructions and morphometric analyses of nearly complete Neanderthal pelves from Sima de las Palomas del Cabezo Gordo (Spain) and Dederiyeh Cave (Syria), comparing them with other Neanderthals and modern humans. We find that Neanderthal and human pelves differ in overall shape from an early age but share similar sexual dimorphism patterns with humans. Pelvic regions associated with childbirth exhibit comparable functional morphology, suggesting similar birth mechanisms. Conversely, locomotor-related features such as hip joint orientation and muscle moment arm geometry differ, indicating distinct stance and gait adaptations. Our findings are consistent with the hypothesis that evolutionary constraints traditionally framed as an "obstetrical dilemma" may have involved a trade-off between childbirth and pelvic floor stability, rather than between childbirth and locomotor performance.