July 20, 2011

Humans May Have Walked Upright 2 Million Years Earlier

Scientists at the University of Liverpool discovered ancient footprints that show human-like features of the feet and gait existed two million years earlier than previously thought.

Earlier studies suggested that the characteristics of the human foot, such as the ability to walk upright, emerged in early Homo, which was about 1.9 million years ago.

However, the Liverpool researchers have shown that footprints of a human ancestor dating back 3.7 million years ago show features of the foot with more similarities to modern humans than with the type of bipedal walking used by chimpanzees, orangutans and gorillas.

Dr Bill Sellers, from the University of Manchester's Faculty of Life Sciences, said in a statement:  "The Laetoli footprint trail is a snapshot of how early human ancestors used their feet 3.7 million years ago."

The footprint site contains the earliest known trail made by human ancestors and includes 11 individual prints in good condition.  Previous studies based their results on single prints and have been liable to misinterpret artificial features like erosion and the environmental factors.

The researchers used a new technique based on methods employed in functional brain imaging.  They also compared data from studies of footprint formation and under-foot pressures generated from walking in modern humans and other living great apes.

"By using a new technique for averaging footprints, foot pressure information from modern great apes, and computer simulation of walking in the proposed Laetoli printmaker, we can see that the evidence points to surprisingly modern foot function very early on in the human lineage," Sellers said in a statement.

Professor Robin Crompton, from the University of Liverpool's Institute of Ageing and Chronic Disease, said in a statement: "It was previously thought that Australopithecus afarensis walked in a crouched posture, and on the side of the foot, pushing off the ground with the middle part of the foot, as today's great apes do.

"We found, however, that the Laetoli prints represented a type of bipedal walking that was fully upright and driven by the front of the foot, particularly the big toe, much like humans today, and quite different to bipedal walking of chimpanzees and other apes.

The research was published in the Royal Society journal Interface and funded by the Leverhulme Trust and the Natural Environment Research Council.


Image 2: Computer simulation was used to predict the footprints that would have been formed by the likely printmaker, a species called Australopithecus afarensis


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