Israeli study reveals: Why do men and women walk differently?
A study led by a researcher from Tel Aviv University offers an evolutionary explanation for the differences in pelvic structure: in the modern male, a spring-like biomechanical mechanism has developed that absorbs shocks, stores energy, and makes long-distance walking more efficient. So why is the situation different for women?
For many years, science has tried to understand why the pelvis of women and men developed into different structures. Now, a new study suggests changing the perspective: it is not the Neanderthal pelvis that is the exception, but rather that of the modern male. The researchers suggest that during evolution, a unique biomechanical mechanism developed in men that acts like a natural spring — absorbing shocks, storing energy, and returning it with every step, thereby potentially making long-distance walking more efficient. The study was published in the journal Scientific Reports.
The study, led by Prof. Yoel Rak from the Department of Anatomy and Anthropology at Tel Aviv University, was conducted in collaboration with researchers from Spain, the Technion, Bar-Ilan University, and Ono Academic College. The research was based on a comparison between two almost complete Neanderthal male pelves, discovered in the Kebara Cave in Israel and at the Sima de los Huesos site in Spain, and dozens of modern human pelves. Surprisingly, despite their large dimensions and massive structure, it was found that Neanderthal pelves are similar in most measures to the pelvis of modern women, rather than that of men.
According to the researchers, for many years the Neanderthal pelvis was perceived as an unusual anatomical structure requiring its own functional explanation. However, the new findings change the perspective: it is possible that the ancient structure was preserved precisely in Neanderthals and in human females, while the modern human male pelvis is the one that underwent a significant change and became a unique structure. The central finding of the study is that the hip joints of the modern human male are located more anteriorly on the pelvic ring compared to both the human female and the Neanderthal male. This change created a new mechanical system in which the anterior hip muscles, which attach to the front part of the pelvis, act like a spring, while the body weight acts on the back part of the pelvis.
Prof. Rak explained that with every step of a person walking on two legs, the body's center of gravity "falls" slightly downward. This fall creates shocks in the joints and requires energy expenditure to lift the body again for the next step. According to the new model, the unique structure of the male pelvis allows the hip muscles to absorb the fall of the center of gravity, store elastic energy during the step, and return it immediately afterward to "spring" the body for the next step. Thus, according to the researchers, the pelvis becomes a kind of natural shock-absorption system that saves energy, makes walking more efficient, and thereby provides a significant advantage in long treks.
The change in the position of the hip joints also required additional adjustments in the pelvic structure, including thickening of the pubic bone and deepening of the front part of the pelvis to cope with the new loads. The human female, however, cannot adopt the entirety of these changes. According to the researchers, birth constraints require maintaining a relatively shallow pelvis and a wide birth canal, and therefore the female pelvis remained closer to the ancient structure — the same structure found also in Neanderthal males.
Prof. Ella Been from Ono Academic College, who also participated in writing the study, added: "This study demonstrates how questions concerning human evolution are not just about the distant past. Understanding the evolution of our walking mechanism contributes to contemporary research in the fields of biomechanics, musculoskeletal medicine, rehabilitation, and injury prevention. The perspective provided to us by the Neanderthals helps us better understand the modern human body."
Prof. Rak concluded: "The study's findings change the way human pelvic evolution should be understood. It is not the Neanderthal pelvis that is the exception requiring explanation, but rather the modern human male pelvis. The mechanism that developed in it is the evolutionary innovation." The researchers emphasize that this is a new biomechanical model that may explain a significant part of the dimorphism between women and men in pelvic structure, and illustrate that even in human anatomy — the macroscopic one — a field that seems to have been fully researched, it is still possible to uncover unique structures and new, significant geometries.
