Saturday, 31 March 2012

A Revolution In The Story Of Human Evolution

The Burtele remains
Three million years ago, the continent of Africa was covered in plains of tall grass inhabited by small apes. They were under constant threat from predators such as giant cats. As a result, they did something extraordinary: they changed their entire system of locomotion. By walking upright they could spot predators from afar over the tops of the grass. This simple change would eventually result in for our brain power, our ability to speak and our manipulation of tools.

This ape was Australopithecus. Nine species are known to science, but they all share the same characteristics: a skull with the a vertical, vertebral column, with strong hips, legs and feet designed for bipedal locomotion.

This caused excitement in the palaeontological and anthropological world as it provided a link in the chain from tree dwelling simians to ground dwelling, upright-walking apes. For a long time it was thought that they were the first human ancestors to walk in this way.

Recently, however, some scientists believe that an even older hominid, coming in at around five to three million years old, called Ardipithecus was also bipedal. Fragmentary fossils hinted at this, but it was still a tenuous hypothesis. Now fossil evidence shows that the australopithecines were not the oldest hominids to walk on two legs. In 2009, a team of anthropologists excavating at Burtele in the Woranso-Mille area of the Afar Triangle in Ethiopia found a fossil foot.

It was dated to 3.46 million years old using radioactive argon-argon dating, but the lack of cranial remains meant that the researchers did not assign it to a specific species. Yet its age shows that this creature sat somewhere between the ardipithicines and the australopithecines. The foot shows a similar bone structure to that of the australopithecines, but the opposable big toe is that of the ardipithecines. 'This discovery was quite shocking,' said co-author and project co-leader Dr. Bruce Latimer of Case Western Reserve University. 'These fossil elements represent bones we’ve never seen before.'

Analysis showed that the big toe could move from side to side, but there was little development in the joint which would allow for more complex locomotion, such as the push off the ground for upright walking. This would result in a rather lop-sided gait. Further analysis or more fossil remains will allow us to place this creature exactly on the tree of life. Yet its impact on how it may have affected the evolution of humans is revolutionary.