It's the Modern Human Male Pelvis That's Unusual, Not the Neanderthal's, Study Finds

For decades, the Neanderthal pelvis has been treated as an anatomical puzzle requiring its own explanation. A new study by the Department of Anatomy and Anthropology at Tel Aviv University, published in Scientific Reports, suggests the opposite: it is the modern human male pelvis that is the unusual one. Comparing two nearly complete male Neanderthal pelvises, one from Kebara Cave in Israel and one from Sima de los Huesos in Spain, with dozens of modern human pelvises, the researchers found that despite their large size and robust build, Neanderthal pelvises resemble those of modern human females in most measurements and proportions, not modern human males.

The study, led by Professor Yoel Rak with researchers from Spain, the Technion, Bar-Ilan University and Ono Academic College, found that the hip joints of modern human males sit farther forward on the pelvic ring than in modern human females or male Neanderthals. According to the researchers, this shift created a new mechanical system in which the thigh muscles at the front of the pelvis act like a spring, storing energy as the body's center of mass drops with each step of walking and releasing it to help propel the body into the next step, functioning as a shock absorber that may reduce energy expenditure over long-distance travel.

The shift in hip-joint position also required other structural changes, including a thicker pubic bone and a deeper front portion of the pelvis to withstand the new mechanical loads. Modern human females could not adopt this full set of changes because childbirth requires a relatively shallow pelvis with a wide birth canal, so the female pelvis stayed closer to the ancestral configuration also seen in male Neanderthals, the researchers say.

"This study demonstrates that questions about human evolution are not confined to the distant past," said co-author Professor Ella Been of Ono Academic College. "Understanding the evolution of our walking mechanism can contribute to contemporary research in biomechanics, musculoskeletal medicine, rehabilitation and injury prevention." Rak said the findings show that even in human anatomy, a well-studied field, there remains potential to uncover previously unrecognized structures and mechanisms.