the University of Liverpool has shown that the mechanisms of the human foot are
not as unique as originally thought and have much more in common with the
flexible feet of other great apes.
understanding of the evolution of human walking is based on research from the
1930s, which proposes that human feet function very differently to those of
other apes, due to the development of arches in the mid-foot region and the
supposed rigidity of that on the outside edge of the foot.
In a study
of more than 25 000 human steps made on a pressure-sensitive treadmill at the
University's Gait Laboratory, scientists at Liverpool have shown that despite
having abandoned life in the trees long ago, our feet have retained a
surprising amount of flexibility, the type seen in the feet of other great
apes, such as orangutans and chimpanzees, that have remained largely
Robin Crompton, from the University's Institute of Ageing and Chronic Disease,
explains: "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 – our feet differ markedly to those of our nearest
relatives, whose mid-foot is fully flexible and makes regular ground contact.
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."
previously been thought that humans who make contact with the ground with the
mid-foot region are primarily those that suffer from diabetes or arthritis,
both of which can impact on the structure of the feet. Research showed,
however, that two thirds of normal healthy subjects produced some footfalls
where the mid-foot touches the ground, with no indication that this is other
than an aspect of normal healthy walking.
Some new features
Bates, from the University's Institute of Ageing and Chronic Disease, said:
"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.
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.
hypothesise 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."