The most important metatarsal in history: Fossil shows man walked tall 3 million years ago



It was a small step for an apeman, but a giant leap for mankind.

Scientists have pinpointed the moment when our ancestors finally abandoned the trees to walk upright like modern people.

In a breakthrough that helps rewrite human evolution, researchers have found a fossilised foot bone from an early human relative who strolled confidently on two legs more than 3.2million years ago.

The finding ends decades of debate about when our ancestors first began to walk like modern man, rather than clambering around the trees like gorillas and chimps.

Breakthrough: Researchers have found a fossilised foot bone from an early human relative who walked on two legs more than 3.2million years ago Proof: The bone found is the fourth metatarsal, which helps connect the toes and foot muscle to the rest of the skeleton

The bone belonged to Australopithecus afarensis - a creature best known from the discovery of 'Lucy', whose partial skeleton was dug up in Ethiopia in 1974.



The fossil shows that Lucy’s feet had fixed arches, a trait only found in humans and which evolve to cope with the strains of running and walking long distances.



'Now that we know Lucy and her relatives had arches in their feet, this affects much of we know about them, from where they lived to what they ate and how they avoided predators,' said Dr Carol Ward, professor of integrative anatomy at the University of Missouri, who led the study.

'The development of arched feet was a fundamental shift toward 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.'

Lucy had a smaller brain and stronger jaw than a modern person. Her species lived between 3.7million and 2.9million years ago and were known to be able to walk on two feet.



However, researchers did not known whether she spent most of their time on all fours, climbing and swinging through trees like monkeys - or whether she walked upright like people.

A 3-D model of the 3.2 million-year-old hominid known as Lucy, whose partial skeleton was discovered in 1974. The new evidence proves she walked upright

The newly discovered bone is a complete fourth metatarsal - one of the long bones that connects the toe to the base of the foot.



The bone shows that Lucy’s family had stiff, arched feet strong enough to push off against the ground, and flexible enough to absorb shock.



With human-like arches in its feet, Australopithecus afarensis was able to roam the countryside and leave the forest to forage for food when necessary.



With its strong jaws, Australopithecus could also eat several types of food, including fruit, seeds, nuts and roots. Combining their strong jaws and their new skill of walking, Lucy and her relatives were able to live in open areas as well as wooded ones.

Australopithecus was a new kind of creature - very different from earlier species like Ardipithecus ramidus, which came before Lucy and which moved on all fours, or upright, depending on the situation.

Location: The fossilised foot bone from an early human relative who walked on two legs was found in Egypt

'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,' Dr Ward said.



'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 discovery of the bone, at Hadar Ethiopia, is reported in the journal Science.

Before the discovery of Lucy in the 1970s, fossil experts argued that Homo erectus - an ancestor living from 1.8 million to 70,000 years ago - was the first member of the family tree to walk properly upright.



The new study confirms that the date for confident upright walking is between one and two million years earlier.

Dr Ward said: 'We have know that Australopithecus were thus first committed upright biped, but have long debated whether they also spent significant time climbing trees, and whether their anatomy and movement reflected this compromise.

'This new fossil provides strong evidence that their stiff, arched feet were fully humanlike and that they had relinquished proficient climbing abilities in favor of a commitment to life on the ground.'

