A reconstruction of the unwarped skull should make Toumai's features clearer. Credit: © M.Brunet

Toumaï, this summer's celebrity skull, has drawn a bitter accusation - that the human-like creature was actually a female gorilla.

When the 6-7-million-year-old fossil was unveiled earlier this year, its face glowered from cover pages worldwide. Toumaï was proclaimed as the oldest fossil from a member of the human family - a desperately sought lead into the murky dawn of human evolution.

But Milford Wolpoff and his colleagues dispute the claim that Toumaï is human-like, or hominid. They argue that the skull's features are more like those of an ancestral gorilla1. The case that Toumaï's discoverers make for it being hominid is "unconvincing", says Wolpoff, an anthropologist at the University of Michigan in Ann Arbor.

Other experts, however, are not swayed by the ape argument. "I don't think there's any chance it's a gorilla,'' says anthropologist Bernard Wood of George Washington University in Washington, DC.

Two of the accusing group last year unearthed a 6-million-year-old fossil, Orrorin tugensis. This find's hominid status also met with scepticism.

Head to head

The row centres on Toumaï's skull, particularly a flat plane at the back, where the neck muscles once attached. Wolpoff claims that the plate is at a steep angle - a sign that the muscles must have pointed along the back of a four-legged animal.

Toumaï's discoverers, Michel Brunet and his team of the University of Poitiers in France, counter that the actual skull is warped and that, when undistorted, the plane leans towards the horizontal. This suggests that the attached muscles threaded down the spine, as they would for a creature walking upright2.

Toumaï doesn't have to be related to something alive today Bernard Wood , George Washington University

Other features are also causing clashes. Brunet thinks that Toumaï's teeth, for example, are characteristic of a hominid. Wolpoff and his colleagues argue that they could be those of a female ape. "We're looking at the same features and weighing their importance differently," admits Wolpoff.

In fact, Toumaï may not be a direct predecessor of either human or gorilla, points out Wood - it could lie on an evolutionary dead-end that sprouted from one of the lineages. "It doesn't have to be related to something alive today."

A forthcoming model of the undistorted skull should help to resolve the debate, thinks anthropologist Daniel Lieberman of Harvard University in Boston, Massachusetts. "A lot of people are rightly ambivalent," he says. "People need to see the reconstruction."