Sahelanthropus tchadensis is the name of a Hominidé Bipède whose first specimen was called Toumaï. Discovered with the Chad, its age is estimated at 7 million years.

Conditions of the initial discovery

The discovery of Sahelanthropus tchadensis is the fruit of a search for several years undertaken by Michel Brunet, paleoanthropologist, professor at the university of Poitiers. It explores the West Africa and in particular the Cameroun in the search of sedimentary geological layers old from 6,5 to 7 million years likely scientifically to test the theory of the “East Side Story” proposed by Yves Coppens, which describes the appearance of the first Hominides in East Africa. In 1992, the National center of Support to the Research of the Ministry for the Higher education of the Republic of Chad invites it for a conference and proposes to him to take part in missions of ground. Its first mission will take place in 1994. In 1995, at the time of his second mission, a driver of the Management of the Mines will discover Abel ( Australopithecus bahrelghazali ).

Systematic excavations will develop then in the sector of Koro-Toro and will allow a team of four men in service the National center of Support the Research of Chad (Alain Beauvilain, doctor d' État), Fanoné Gongdibé (field engineer of the Ministry for the Mines), Ahounta Djimdoumalbaye (laid off in natural science, free-lance with the CNAR) and Mahamat Adoum (not graduate, employee with the CNAR) to put at the day on July 21st, 2001 the cranium of Toumaï in the sector of Toros-Menalla on a new site, TM 266.

Characters of the species

For the characteristics of the first discovered specimen, to see the detailed article Toumaï

To date, the known morphological elements remain limited. A complete cranium, isolated mandibles and teeth having been put at the day, it is possible to reconstitute the head but not to have that a more general idea for the remainder of the body. Its cranial capacity, about 350 cm ³, is equivalent to that of the current chimpanzees.

The fastening of Toumaï to the branch of the Hominidé S is not a doubt for the free-Chadian team which put it at the day (of which Alain Beauvilain). For Brownish Pr, which undertook the scientific study of the fossil Toumaï , the analysis of the Canine S and the know-orbital pad shows it clearly. Moreover, although its low cranial capacity (about 350 cm ³) brings it closer to the Chimpanzé, certain characters of the face of Sahelanthropus tchadensis are more advanced than those of more recent Hominides. Finally, the teeth (in particular incisors and first premolars) indicate a food more varied than that of the majority of the monkeys (rather fructivores and herbivores).

However, certain scientists, like Brigitte Senut, Martin Pickford,… , suggest that the Sahelanthropus tchadensis would not be a precursor of the man but an ancestor of the large current monkeys. The absence of other elements of skeleton indeed returns the analysis of professor Brunet difficult to support. But even if Toumaï were the ancestor of a monkey, this discovery would remain an extraordinary event. On the other hand, if Sahelanthropus tchadensis one is hominidé, it is very close to the divergence man/monkey evaluated with - 7 million years.

The Bipédie of Sahelanthropus tchadensis is not a doubt for its discoverers. Indeed the occipital foramen corresponds to that of a rectified spinal column. However the current absence of remainders other than cranium, the fragments of mandibles and the isolated teeth does not make it possible yet to be categorical on this point (the bipédie is not confirmable as long as the analysis of a bone of the leg or basin is not carried out).

Sahelanthropus tchadensis and Australopithecus

It seems well established that the difference in age and the differences morphological between Sahelanthropus tchadensis and the Australopithèque S are important and that they are two different kinds. That contradicted the theory of the East Side Story of Yves Coppens and makes it possible to imagine a development of the Hominidé S in several parts of the Africa rather than in its only area Is.

The phylogenetic bonds are undeniable, but their true nature remains so discussed that it is difficult to carry out a kind of Family tree. Undoubtedly it will still be necessary many discoveries to make it possible to bind precisely the kinds Homo and Australopithecus with what one calls the “Hominides of higher Miocène”, of more than 5,5 million years.

“Hominides of higher Miocène”

An important matter remains posed: is it necessary to gather Sahelanthropus tchadensis , Orrorin tugenensis and Ardipithecus kadabba in only one kind?

Today (in 2006), nothing makes it possible to answer. Indeed, the remainders found for these three forms are hardly recut (cranium for Sahelanthropus tchadensis , jawbone, teeth, shoulder, femurs for Orrorin tugenensis , teeth, arm and some other small bones for Ardipithecus kadabba ). Research in progress in the three countries of discovered (Chad, Kenya and Ethiopia) should help to solve this problem in the years to come.

See too

• Paléoanthropologie

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