Neanderthal heel bones point to flatter feet than in Homo sapiens, Journal of Human Evolution study

Researchers have described the outer shape of a complete Neanderthal heel bone in detail for the first time and compared it with Homo sapiens bones, Naked Science reports. The work, published in the Journal of Human Evolution, used seven calcaneus bones of Homo neanderthalensis and 64 Homo sapiens samples naked-science.ruNaked Sciencenaked-science.ruOpen source ↗. The authors conclude that Neanderthals probably had a foot partly similar to that of people diagnosed with flat feet.

Heel bone: sample and method

The calcaneus is the largest bone of the foot, located directly under the ankle, and it absorbs the impact at every step. The Homo sapiens bones came from different periods: Pleistocene hunter-gatherers, Iron Age farmers and gatherers, and city residents of the industrial era. The bones were scanned with computed tomography and laser methods and carefully photographed. From these data the team built detailed digital models and compared the heels of the two species with three-dimensional geometric morphometrics.

What differed in the Neanderthal foot

The Neanderthal heel turned out to be shorter along the foot, wider and taller than the human one. According to the bone geometry, Neanderthals probably took a different approach to stability and posture and regularly stood in deeper pronation, in which the foot and heel tilt inward toward the central axis of the body. The authors also suggest a lower lateral longitudinal arch, which runs from the base of the little toe to the heel, and consider that it gave more flexibility in the central part of the foot.

Neanderthal bodies were muscular with a large bone mass, and the authors believe these people were constantly physically active. Their heel bone resembled samples of Homo sapiens with considerable excess weight naked-science.ruNaked Sciencenaked-science.ruOpen source ↗. The closest to Neanderthals were prehistoric hunter-gatherers, who covered long distances barefoot or in soft footwear. Industrial-era city residents have a weaker heel bone, which the researchers linked to a sedentary lifestyle and regular use of rigid footwear.

The authors read the robust heel as an adaptation to carrying loads and to flexibility between parts of the foot when walking on uneven surfaces. They stress that the hypothesis needs to be rechecked: conclusions cannot be drawn from the outer appearance of the heel bone alone, and further research is needed.

The publication adds that a flatter foot makes a stress fracture easier to get, especially when running long distances uphill or downhill. Examples of such fractures exist in early Neanderthals (Homo heidelbergensis). For Pleistocene Homo sapiens, skeletons with traces of stress fractures have not yet been found, although more of their skeletons are known than Neanderthal ones.