The feet of humans and apes are more similar than we once thought.
A 1930s study concluded human's feet were much different from apes. Researchers put people on treadmills to prove them wrong, a University of Liverpool press release reported.
Scientists formerly believed primates had more flexible feet than humans; this new study shows our feet have retained much of the suppleness from our tree-dwelling days.
The team analyzed over 25,000 human steps taken on special pressure-sensitive treadmill.
"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," Professor Robin Crompton, from the University's Institute of Aging and Chronic Disease, said. "This supposed 'uniqueness', however, has never been quantitatively tested. 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."
The researchers believe human ancestors most likely developed flexibility in their feet to move quickly through trees. Once they transitioned to land, they developed new features for easy movement instead of losing the old ones.
"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. 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," Dr. Karl Bates, also of the Institute of Aging and Chronic Disease, said.
"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. 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," he said.
