August 21, 2013
Human Feet Very Similar To Those Of Great Apes
Brett Smith for redOrbit.com - Your Universe Online
As humans, we tend to think of ourselves as much more evolved than our fellow primates. However, new research from biologists at the University of Liverpool has revealed the human foot is much closer to the feet of great apes than previously thought.
The study looked at the mechanics of the foot, the knowledge of which is based primarily on research conducted in the 1930s. Conventional models assert the evolution of arches in the mid-foot and the supposed rigidity on the outside edge of the foot causes our feet to function much differently than those of great apes.
In the new Liverpool study, scientists at the University’s Gait Laboratory analyzed more than 25,000 human steps made on a specially designed, pressure-sensitive treadmill. According to the team’s report, published in the Proceedings of the Royal Society B, the analysis showed our feet have maintained a surprising amount of flexibility like that found in other great apes that have remained largely tree-dwelling.
"It has long been assumed that because we possess lateral and medial arches in our feet - the lateral one supposedly being rigid and supported in bone, that our feet differ markedly to those of our nearest relatives, whose mid-foot is fully flexible and makes regular ground contact,” said co-author Robin Crompton, from the university's Institute of Ageing and Chronic Disease.
"This supposed 'uniqueness', however, has never been quantitatively tested,” Crompton continued. “We found that the range of pressures exerted under the human mid-foot, and thus the internal mechanisms that drive them, were highly variable, so much so that they actually overlapped with those made by the great apes."
Scientists have seen evidence of humans making contact with the ground in the mid-foot region as they walk, but those observations were primarily made of individuals with diabetes or arthritis, two conditions that can affect the structure of the foot.
However, the new study showed two thirds of healthy subjects made some footfalls that included some portion of the mid-foot touching the ground, causing the scientists to conclude this is typical of normal healthy walking.
"Our ancestors probably first developed flexibility in their feet when they were primarily tree-dwelling, and moving on bendy branches, but as time passed and we became more and more ground-dwelling animals, some new features evolved to enable us to move quickly on the ground,” said Karl Bates, from the University's Institute of Ageing and Chronic Disease.
"Our limbs, however, did not adapt to life on the ground anywhere near as much as those of other ground-dwelling animals such as horses, hares and dogs,” Bates added. “Our tests showed that our feet are not as stiff as originally thought and actually form part of a continuum of variation with those of other great apes.
"We hypothesize that despite becoming nearly exclusively ground dwelling we have retained flexibility in the feet to allow us to cope effectively with the differences in hard and soft ground surfaces which we encounter in long distance walking and running,” Bates concluded. “The next part of our study will be testing this theory, which could offer a reason why humans can outrun a horse, for example, over long distances on irregular terrain."