Walk like a Cro-Magnon

Long ago our ancestors left the forests and began to walk tall on two feet - and now scientists think they might soon be able to pinpoint when.

A team of South African and other scientists, using advanced scanning technology and statistical analysis, have developed a new way of looking at bones that enables them to work out just how our distant relatives walked.

"This approach shows tremendous research potential for bone biologists and morphologists, particularly those interested in limb structure," said researcher Tea Jashashvili, of the Wits Evolutionary Studies Institute.

In a paper that appeared in the journal PLoS One, the interdisciplinary team analysed differences in the feet and legs of humans, chimpanzees and gorillas. The coloured maps generated by the scans showed different bone densities, which pointed to each species' unique locomotion.

"It's very exciting. We can capture differences inside bones and look at the internal structures," said Kristian Carlson, also from the evolutionary studies institute.

Bipedalism, walking upright on two feet, is seen as a unique human trait made possible, said Carlson, by a foot-loading mechanism in which the foot acts as a spring, propelling the human forward.

In the next phase of the study the team wants to go back in history and examine fossils of our ancestors. They want to find evidence of the foot-loading mechanism they used to establish whether they walked as we do today.

"We will be looking to see when the pattern changes, and looking for when the [modern] foot-loading mechanism appears," said Carlson.

Their technique could also be used to pinpoint when our ancestors abandoned their arboreal life.

They also plan to look into our more recent past, and study 100000-year-old skeletons excavated at the Klasies River mouth, near Humansdorp, in Eastern Cape. This will give them a glimpse of a time when humans were not seated behind desks wearing shoes.

Although they would be anatomically little different to modern humans, their more mobile lifestyle might be evident in scans of their bones.

"If they exhibit something different, that would be exciting," said Carlson.