The question of whether a 7-million-year-old primate, nicknamed 'Toumai,' walked on two or four legs has whipped up drama amongst palaeontologists - complete with a vanishing femur.
Since the discovery of Sahelanthropus tchadensis's first fossil back in 2001, it has often been cited as our earliest known hominin ancestor. Initial analysis suggested that Sahelanthropus regularly walked upright and had a combination of ape-like and human-like features.
These conclusions, however, were based on a single skull.
The skull has anatomical features that potentially indicate this primate had an erect spine, and therefore spent some of its time walking on two legs only. Its small teeth also appear more human than ape-like. A later reconstruction supported these findings.
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