Standard image of the new scientist

Our supposedly earliest human relative may have walked on four legs

By Michael Marshall

The shape of the femur of Sahelanthropus tchadensis is typical of monkeys such as chimpanzees

Franck Guy / University of Poitie

After more than a decade in the limbo, a crucial fossil of an early human relative has finally been scientifically described. The leg bone suggests that Sahelanthropus tchadensis, the earliest species commonly considered early human or hominin, did not walk on two legs and therefore may not be a hominin at all, but was more related to other monkeys such as chimpanzees.

A paper by a competitive group that has not yet been reviewed by experts denies this. The studies are the latest twist in …