Similarly, the sacrum is broad (providing a stable element between the sacroiliac and coxofemoral joints) and curved inwards (in humans and probably in Lucy too), thus helping to improve not only balance in a bipedal posture by lowering the centre of gravity, but also support for the viscera by reducing the surface area of the perineum. The broad spread of the iliac wings in Lucy and Homo sapiens is likely a sign of evolution to support the viscera. The pelves of Lucy and the modern woman are anteroposterior in orientation, unlike those of the great apes, which are cranio-caudal. As described above, the pelvic morphology of Lucy, great apes and Homo sapiens differs considerably: Lucy ’ s pelvis is described as being platypelloid, while the planes in those of the great apes are seen to be aligned one beneath the other, forming a cylinder. However, insight into the pelvic anatomical evolution from a quadruped posture (where viscera are mainly sustained by the abdominal wall) to an upright position with walking (where viscera are supported by the pelvic floor) may contribute to a better understanding of the genesis of genital prolapse. Of course, we know that genital prolapse is multifactorial. In the current study, we present an evolutionary aspect of the bony pelvis and its relationship with genital prolapse. We had studied the obstetrical mechanics of Lucy s pelvis previously and concluded that delivery was likely dystocic, but possible in this platypelloid pelvis with some adaptive processes (overlapping of the sutures of the foetal skull, asynclitism, cephalic flexion, nutation and counter-nu- tation, and specific delivery positions such as standing or squatting). 3) and fairly small ischial tuberosities made Lucy more similar to Homo sapiens and less like the great apes. The exis- tence of a protruding ischial spine (Fig. The sacrum was larger than in great apes with a small concavity (probably underestimated because of post-mortem damage). By contrast, the Australopithecine pelvis of Lucy was short and very broad (all the transverse diameters were considerably greater than the anteroposterior diameters) and was termed platypelloid. However, their sacrum was narrow (compared with Lucy and the modern woman) and the sacral concavity (estimated on the basis of the sacral curvature) was shallow in chimpanzees and deeper in gorillas. All the anteroposterior diameters of the three pelvic planes were large in great apes owing to the lengthened caudal portion of the ilium. Gorillas had a long, broad pelvis, while in chimpanzees it was long and narrower. Sacral curvature was the least in the chimpanzee (0.82 cm) and the greatest in modern females (2.01 cm). The sacrum was the broadest in modern females (11.64 cm). The subpubic angle was the narrowest in Lucy, while it was greater than 90° in great apes. Lucy ’ s pelvis shape was the most transversely oval at each plane (index 100 %) except for the gorilla, where the outlet was round or slightly transversely oval (index 3 = 92.11). The results are shown in Table 1 and Fig. Variables were compared using the Wilcoxon rank sum test. analysis was performed on SAS statistical software (SAS 9.1 SAS Institute, Cary, NC, USA).
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