A new Israeli-Spanish study challenges a long-held assumption about one of the major physical differences between men and women: the shape of the human pelvis.
Published in the peer-reviewed Scientific Reports, the study compares Neanderthal pelvises with those of modern humans and suggests that the major evolutionary change may have occurred in the modern male pelvis.
The study was led by professor Yoel Rak of Tel Aviv University’s Department of Anatomy and Anthropology, with researchers from Spain, the Technion, Bar-Ilan University and Ono Academic College.
The team compared two nearly complete male Neanderthal pelvises with dozens of modern human pelvises. One Neanderthal pelvis was found at Kebara Cave on Mount Carmel in northern Israel, while the other came from the Sima de los Huesos (“Pit of Bones”) site in northern Spain.
Despite their large size and robust bones, the Neanderthal pelvises were more similar in most measurements and proportions to modern human female pelvises than to male ones.
For decades, scientists have viewed the Neanderthal pelvis as unusual. The new study suggests that it may instead have retained an ancestral form also found in modern human females, while the modern human male pelvis underwent significant evolutionary changes.
The key difference involves the hip joints. In modern human males, the joints are positioned farther forward than in modern human females and male Neanderthals. According to the researchers, this shift created a natural shock-absorbing system. As a person walks upright, the body’s center of mass moves downward with each step. The thigh muscles absorb some of this movement, storing energy and releasing it to help propel the body into the next step.
The researchers say this system may reduce the energy required for walking, particularly over long distances. The shift also resulted in a thicker pubic bone and a deeper front section of the male pelvis, helping it withstand additional forces.
The researchers say the female pelvis could not undergo the same changes because childbirth requires a relatively shallow pelvis and a birth canal wide enough for a baby to pass through. As a result, it remained closer to the ancestral form also seen in male Neanderthals.
“Understanding the evolution of our walking mechanism can contribute to contemporary research in biomechanics, musculoskeletal medicine, rehabilitation, and injury prevention,” said professor Ella Been of Israel’s Ono Academic College. “The perspective provided by the Neanderthals helps us better understand the modern human body.”
