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January 28, 2022

Shorter legs helped Neanderthals hike

By Mo-Yu Zhou | November 2, 2011

It is well known that Neanderthals had legs that were lower and significantly shorter than those of the typical modern humans. However, most studies in the past concluded that this was due to the cold climate they lived in, as shorter legs reduce the surface area through which heat could escape. Yet new research at Hopkins recently revealed an alternative account: that their shorter lower legs might have been advantageous to Neanderthals, aiding them in moving over mountainous terrain.

This study, conducted by Ryan Higgins and Christopher B. Ruff of Hopkins's Center of Functional Anatomy and Evolution, was published in the online and print editions of the American Journal of Physical Anthropology.

Previous research using human subjects on flat treadmills showed that Neanderthals would have been less efficient than the average human in navigating flat land. However, past studies concerning Neanderthal navigation mostly pertained to their movement on flat land. At the same time, other studies have shown that Neanderthals were less likely to use plains and more likely to use rock shelters or caves than modern humans.

Keeping these studies in mind, the researchers focused on Neanderthal movement over more rigorous terrain. "[We] became interested in the following question: did Neanderthals have a locomotor disadvantage in the (sloped and rugged) areas that surround most of their sites?" Higgins wrote in an email to The News-Letter.

To investigate this, Higgins and Ruff mathematically modeled human walking patterns for both flat and uphill walking. Their results showed that the average Neanderthal would need to take more steps to walk on flat terrain, but not on sloped terrain. In other words, the disadvantage that Neanderthals had on flat land did not apply to mountainous terrain.

This phenomenon exists because people with shorter lower legs do not need to move their legs as high when walking uphill, which reduces the amount of effort they need to expend on swinging their legs and pulling their bodies up when walking. In the cold mountainous areas that Neanderthals tended to live in, this translated to a thermoregulatory advantage.

While this concept, according to Higgins, was "intuitive," he also comments that the impact had previously been uncertain. "It was completely unclear before the analyses if the effect would be big or small," Higgens wrote. However, the results showed that the disadvantage that lower leg lengths would have on flat terrain was completely cancelled out on sloped terrain, rather than just slightly diminished.

These results did not only apply to one species, but presented a pattern over multiple species, as the research also shows. Different types of bovids – for example, gazelles, antelopes, goats, and sheep – which have similar leg construction and experience both a mix of warm and cold weather and live in both flat and hilly terrain, were examined based on existing literature. It turns out that the bovids' leg patterns indicate that the bovids that live on mountainous terrain had shorter lower legs than bovids on flatter terrain, regardless of climate.

The research has several implications. It suggests that, contrary to what previous studies might suggest, Neanderthals were not at a disadvantage in terms of efficiency of movement. More broadly, this study hints at a wider biological rule. "Our study suggests that you can predict that animals who live in more mountainous environments will have shorter lower leg segments compared to their flat terrain counterparts (regardless of climate)," Higgens wrote.

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