The March 4th Issue of PNAS will confirm a radiochronological date for Toumaï

I remember reading the announcement of Sahelanthropus tchadensis (a.k.a. Toumaï) in 2002.The Toumaï Cranium It was an exciting time. A cranium is hard to find and is a quite noteworthy for any early hominid. So, it wasn’t surprising that Nature published the findings, “A new hominid from the Upper Miocene of Chad, Central Africa.” But they did so without a firm antiquity for the fossil! See, the primary publication set an estimation of 6 to 7 million years old based upon associated fauna found in the same horizon. No other dating technique was published.

With the possibility of 7 million old date, this fossil threw a big spoke in our understanding of early hominid evolution. Critics weren’t shy to voice their protest. They said the cranium was too squashed to confirm it was a hominid. A virtual reconstruction of the cranium did little to convince anyone. Paleonathropology was still reserved and not willing to fully accept Toumaï as a hominid. If Toumaï was really a hominid, then that would mean when we considered the human-chimpanzee divergence occured to be wrong. All our molecular clocks would be wrong too.

Well, according to this AP release, our anticipation for a real tangible date for the Toumaï should be resolved in next week’s issue of PNAS,

“French fossil hunters have pinned down the age of Toumai, which they contend is the remains of the earliest human ever found, at between 6.8 and 7.2 million years old…

‘The radiochronological data concerning Sahelanthropus tchadensis … is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock,’ Brunet wrote in a study which will appear in the March 4 edition of the Proceedings of the National Academy of Sciences.

‘Thus, Sahelanthropus tchadensis testifies that the last divergence between chimps and humans is certainly not much more recent than 8 Ma (million years ago.)'”

Wow, I can’t wait. You can be sure to expect me hitting the refresh page and hammering PNAS servers to download a copy of the paper when it comes out. In the mean time, all we have to pine over is the press release, “Oldest hominid discovered is 7 million years old: study.”

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