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Sahelanthropus tchadensis is a fossil hominin classified as the oldest possible member of the human family tree, thought to have lived between approximately 7 and 6 million years ago in the Miocene. The fossils found indicate a relatively small cranium, five pieces of jaw, and some teeth, make up a head that has a mixture of human and chimpanzee features were discovered in the desert of Chad, Djurab erg. A team of four people, three chadian, Mahamat Adoum, Ahounta Djimdoumalbaye, who found the skull the 19 july 2001, Fanone Gongdibe, and the french Alain Beauvilain, leader of this team, found all the fossils of sahelanthropus from july 2001 to march 2002. The braincase suggests a chimpanzee-like intelligence, being only 340cc to 360cc in volume, but the teeth are closer to those of humans, and the face includes brow ridges, a human feature not found on any living great ape. Due to the distorted matrix of the cranium, a 3D computer reconstruction has been produced. The point at the back of the skull where the neck muscles attach (mastoid process) suggests that this species walked upright or likely in between human and chimp posture.

The discoverers claim that S. tchadensis is the oldest known human ancestor after the split of our line from that of chimpanzees. The bones were found in Chad, far from most previous hominin fossil finds, i.e. Eastern and Southern Africa. However, an australopithecine mandible was also found in Chad by Sahelanthropus' discoverers in 1993 belonging to Australopithecus bahrelghazali.

Perspective

The fossil skull BH-029, nicknamed "Toumaï" ("hope of life" in the local Goran language of Chad), may be a common ancestor of humans and chimpanzees, though unlikely to be the most recent common ancestor, as evidence from the molecular clocks suggest humans and chimps diverged 1-2 million years after S. tchadensis (5mya). This find complicates the picture of the human family tree. In particular, if Toumaï is a direct human ancestor, his facial features bring the status of Australopithecus into doubt. Another possibility is that Toumaï is anatomically related to both humans and chimpanzees, but the ancestor of neither. Brigitte Senut, the discoverer of Orrorin tugenensis claims that the features of S. tchadensis are consistent with a female proto-gorilla. Even if Senut's claims are true the find would still be significant; there have been no chimp or gorilla ancestors to be found anywhere in Africa and light would be shed on their family trees.

References

• Michel Brunet, Franck Guy, David Pilbeam, Hassane Taisso Mackaye, Andossa Likius, Djimdoumalbaye Ahounta, et al. "A new hominid from the upper Miocene of Chad, central Africa". Nature, 418:145-51, 2002.
• Nature, "The look of Toumaï", 7 April 2005, pp. 752-755, ISSN 00280836

External links

• Fossil Hominids: Toumai
• National Geographic: Skull Fossil Opens Window Into Early Period of Human Origins

• Early hominids
• Miocene