Ancestors of modern man were walking on two feet up to 3.2 million years ago, new analysis of a fossilised foot bone has revealed.
Researchers studying a fourth metatarsal discovered in Ethiopia found that man’s predecessors had foot arches, meaning they walked as we do rather than swinging from trees. It is thought the discovery could change how scientists view human evolution.
Carol Ward, researcher in the department of pathology and anatomical sciences at the University of Missouri, which carried out the study with colleagues at Arizona State University, said: “Now that we know Lucy and her relatives had arches in their feet, this affects much of what we know about them, from where they lived to what they ate and how they avoided predators.
“The development of arched feet was a fundamental shift towards the human condition, because it meant giving up the ability to use the big toe for grasping branches, signalling that our ancestors had finally abandoned life in the trees in favour of life on the ground.”
The species, Australopithecus afarensis – often referred to as Lucy, the nickname of the most complete fossil of the kind yet found – had stiff, arched feet similar to humans, the research published in the journal Science confirmed.
The fact that the species could walk upright meant they could forage for food when needed instead of being restricted to the forest.
Dr Ward added: “Arches in the feet are a key component of human-like walking because they absorb shock and also provide a stiff platform so that we can push off from our feet and move forward.
“People today with ‘flat feet’, who lack arches, have a host of joint problems throughout their skeletons. Understanding that the arch appeared very early in our evolution shows that the unique structure of our feet is fundamental to human locomotion.
“If we can understand what we were designed to do and the natural selection that shaped the human skeleton, we can gain insight into how our skeletons work today. Arches in our feet were just as important for our ancestors as they are for us.”
The foot bone studied is the only one of its kind believed to be in existence. More excavation work being carried out in Hadar, Ethiopia, is “absolutely crucial for understanding how our species evolved”, Dr Ward said.