In the Koro Toro fossiliferous area, KT 12 locality (16°00′N, 18°53′E) was the site of discovery of (Toumaï).At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3–3.5 Ma) at KT 12 and late Miocene (≈7 Ma) at TM 266. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock. Localities investigated in this area include TM 266 and TM 254 (Fig. The Kollé (KL), Kossom Bougoudi (KB), and Koro Toro (KT) fossiliferous areas were specifically studied to calibrate the authigenic Be dating method by direct comparison with biochronological estimations of co-located mammalian assemblages.

sahelanthropus tchadensis dating techniques-76

U.) after a very common, large anthracotheriid, (5) that it contained. Recent investigations conducted at another locality, TM 254, ≈18 km west of the Ar dating, is not exposed at TM 266; therefore, 20 intermediate geological sections between TM 266 and TM 254 have been documented to determine its stratigraphic position within the A. The sections are uniform in facies across the transect. Geological correlations between TM 266 and TM 254 are firmly supported by the same continuity of stratigraphy between the sites, reflecting a similar environment and climate change history (5).

The base of the mapped sections consists of a well developed, thick, aeolian facies (8). U.) is composed of poorly cemented sand and argillaceous sandstone alternation characterized by dense networks of root tubules/root molds (palaeosols) and termite nests (9, 10). The uniform stratigraphy at the TM localities allowed us to use absolute ages from both TM 266, where Toumaï was discovered, and TM 254 to assign an age to Toumaï.

(Toumaï) (1, 2) have changed substantially the understanding of early human evolution in Africa (1–4).

The sedimentary unit from which Toumaï was unearthed was named the anthracotheriid unit (A. also contains a mammalian fauna that includes taxa that are more primitive than the Lukeino fauna [Kenya, dating from 6 Ma ago (6)] and similar to the fauna from the lower Nawata Formation of Lothagam [Kenya, 6.5–7.4 Ma ago (7)].

Walking upright may have helped this species survive in diverse habitats, including forests and grasslands.

Although we have only , studies so far show this species had a combination of ape-like and human-like features.

It was hoped that the tephra layer would contain material datable by the Be associates with continental particles, where it decays with a half-life of ≈1.4 million years.

This opens up the possibility to date sedimentary deposits in the range of 0.2 to 14 Ma.

To apply the radioactive decay equation described above, it is thus essential to know the regional initial authigenic Be ratio.

The best way to do this is to measure recent samples deposited in an environmental context similar to that in which the sediments of interest have been deposited, that is, in our case, during periods of major lacustrine extension.

The foramen magnum (the large opening where the spinal cord exits out of the cranium from the brain) is located further forward (on the underside of the cranium) than in apes or any other primate except humans. His small, flat canine teeth are unusual for a male primate -- one of the first unique human traits.