Nature reports:

A battered fossil leg bone discovered more than 20 years ago in Chad is finally making its scientific debut. Researchers say that the remains, described today in Nature, show that a species called Sahelanthropus tchadensis was an ancient human relative that walked on two feet.

At seven million years old, S. tchadensis is a candidate for the earliest known member of the hominin lineage — the evolutionary branch that leads from the common ancestor of humans and chimpanzees to modern humans.

A French and Chadian team discovered S. tchadensis in July 2001, during an expedition in the Lake Chad basin. The key find was a nearly complete, but heavily damaged, skull that was described in Nature the following year.

The skull was nicknamed Toumaï, which means ‘hope of life’ in the Chadian Daza language. Researchers led by palaeoanthropologist Michel Brunet at the University of Poitiers, France, argued that, despite the small, chimp-like size of its brain, Toumaï possessed other features of later hominins, such as in its teeth and face. The probable angle at which the base of Toumaï’s skull would have met its spine also hinted at upright walking on two feet. [Continue reading…]