University of Liverpool - How we did the funky gibbon

Researchers are citing the feet of gibbons as the modern-day equivalents of those on which prehistoric man may have moved about around 2 million years ago. Scientists at the University of Liverpool examined early humans' "flexible" feet, similar to those of today's gibbons, before the arched, rigid foot evolved 1.8 million years ago. It was thought that before human feet developed we would have struggled to walk upright. However, gibbons can do so both on the ground and in trees.