This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A new study by the Department of Anatomy and Anthropology at Tel Aviv University, published in Scientific Reports, offers an explanation for one of the striking differences between men and women: the evolutionary development of the modern human pelvis. By comparing Neanderthal pelvises with those of modern humans, the researchers reached a surprising conclusion: The unusual structure of the pelvis may not be that of the Neanderthal, as has been assumed for decades, but rather that of the modern human male.
According to the researchers, the male pelvis evolved into a unique biomechanical shock-absorbing mechanism that stores energy and makes long-distance walking more efficient. Led by Professor Yoel Rak of the Department of Anatomy and Anthropology at Tel Aviv University and conducted in collaboration with researchers from Spain, the Technion, Bar-Ilan University and Ono Academic College, the study is based on a comparison of two nearly complete male Neanderthal pelvises, one from Kebara Cave in Israel and the other from the Sima de los Huesos site in Spain, with dozens of modern human pelvises. Surprisingly, despite their large size and robust construction, the Neanderthal pelvises were found to resemble those of modern human females in most measurements and proportions rather than those of modern human males.
For many years, the Neanderthal pelvis has been regarded as an anatomically unusual structure requiring a functional explanation of its own. The new findings, however, require a new look at Neanderthal pelvises. The ancestral configuration may have been retained in Neanderthals and in modern human females, while the modern human male pelvis underwent substantial evolutionary modification, giving rise to a distinctive anatomical configuration.
The central finding of the study is that the hip joints of modern human males are positioned farther forward on the pelvic ring than those of both modern human females and male Neanderthals. According to the researchers, this shift created a new mechanical system in which the anterior thigh muscles, attached to the front of the pelvis, function much like a spring, while body weight acts on the posterior part of the pelvis. Rak explains that during every step of bipedal walking, the body's center of mass drops downward.
This drop strains the joints and requires energy to raise the body again in preparation for the next step. According to the new model, the distinctive geometry of the male pelvis enables the thigh muscles to cushion the drop of the body's center of mass, store potential energy during the step and then release that energy immediately afterward—effectively "springing" the body upward into the next step. In this way, the pelvis functions as a natural shock absorber and energy-return system.
It may reduce energy expenditure, improve walking efficiency and thereby provide a significant advantage during long-distance travel on foot. The change in the position of the hip joints also required additional structural adaptations, including the thickening of the pubic bone and deepening of the anterior portion of the pelvis to withstand the new mechanical loads. Modern human females, by contrast, could not adopt the full suite of these modifications.
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