Toumaï: One of the Oldest Known Hominins

Discovery and Scientific Context

The fossil of Toumaï (Sahelanthropus tchadensis) was discovered in 2001 in the Chad Desert by the team led by Michel Brunet (1940-2021). Dated to about 7 million years ago, this skull is one of the oldest known hominins and provides key insights into the divergence between chimpanzees and hominins.

Significance of the Chimpanzee-Hominin Divergence

The divergence between chimpanzees and hominins is estimated at about 6 to 7 million years ago. This separation implies that some morphological and locomotor traits observed in Toumaï may represent an intermediate stage between great apes and early hominins. The study of Toumaï notably shows a more advanced position of the foramen magnum, suggesting partially bipedal locomotion.

N.B.: The foramen magnum is the occipital opening of the skull through which the spinal cord passes. Its position and orientation help estimate posture and mode of locomotion. In quadrupedal primates, it is located posteriorly, while in bipedal hominins, it is more advanced under the skull, indicating that the head is carried above the spine. Fossils like Toumaï have an advanced foramen magnum, suggesting partial bipedalism.

Source: Nature – Sahelanthropus tchadensis and Science Magazine.