‘Flexible’ gibbon feet model for early humans

Scientists have found that early humans could have walked successfully on a flexible flat foot, similar to modern day gibbons.

Early Humans could have possessed a flexible foot, similar to modern day Gibbons

The arched rigid foot of modern humans – thought to have appeared approximately 1.8 million years ago – is best adapted for upright walking, but scientists at the University of Liverpool have found that early humans once had ‘flexible’ feet and could have walked on the ground some years earlier.

Dr Evie Vereecke, from the University’s School of Biomedical Sciences said: “Gibbons have a flexible joint mid-way along the foot that supports them in walking and climbing. Human ancestors also had this joint for tree dwelling and ground walking, but modern humans have now lost its flexibility in favour of a ‘rigid’ foot.”

To understand how successful or restrictive the flexible foot might have been for early humans the team set up a high-speed camera at Belgium’s Wild Animal Park to capture a gibbon’s foot movements. They built a computer model to digitise the footage and analyse the mechanisms employed in the foot and compare it to how humans walk today.

“We found that gibbons hit the ground with their toes first, similar to the ‘forefoot’ strike of professional sprint runners, which stretches the tendons in the toes. We also found that instead of lifting the foot at the end of a stride, the gibbon raised its heel first, making an upward arch and stretching the tendons in the sole of the foot,” explained Vereecke.

These stretched tendons allow storage of elastic energy and once the toe leaves the ground the tendons in the foot recoil, releasing the stored energy and generating the necessary propulsion to push off the ground and walk upright quite successfully.

The work - published in the Journal of Experimental Biology - shows that it is possible that human ancestors could have walked successfully with an upright-gait on a ‘flexible’ flat foot and may have similar energy storage mechanisms to modern humans.