The Brain of Sahelanthropus Tchadensis

Sahelanthropus Tchadensis was a hominin species that lived between 6 and 7 million years ago. In this video we will examine all research related to it's brain size, brain shape and brain function.

Sahelanthropus Tchadensis is a hominin species that is based on the fossil remains of a single skull, several teeth and jaw bones, and a femur. A word of caution: Since only a single skull is available any conclusions we draw from these analyses are tentative.

Analyses after the discovery of S. Tchadensis suggested that it may have walked upright. The foramen mangum, which is the opening where the spinal cord enters the brain, is perpendicular to the skull. In modern chimpazees it is in an acute angle. This may have suggested that S. Tchadensis natural posture was upright. However, analyses on the femur bone do not support the hypothesis that it was a habitual biped.

Furthermore, the brain of S. Tchadensis is long and narrow. This is very different from chimpanzees, but also different to later hominins such as A. Africanus. However, it is similar to another australopithecine, A. Anamensis. Whether there is a link between the species is unknown, but differences in facial features suggest it is unlikely.

The relative size of the cerebellum of S. Tchandensis is very similar to great apes, but different from later hominins and humans. Since the cerebellum is crucial for posture, balance and movement learning, movements of S. Tchadensis were probably not that much different from other great apes. This seems to be in line with the hypothesis that it did not habitually walk on two legs.

Finally, there are aspects of S. Tchadensis brain that are unique, such as the flat shape and horizontal temporal region. It may suggest that it is not in our direct ancestoral path, but this is uncertain.

Time stamps:
0:00 Sahelanthropus Tchadensis skull, fossils and brain
1:40 Sahelanthropus Tchadensis walkig upright?
3:30 Sahelanthropus Tchadensis brain compared to other hominins
7:20 Sahelanthropus Tchadensis cerebellum size
9:28 Sahelanthropus Tchadensis nuchal crest and temporal lobe
10:33 Sahelanthropus Tchadensis brain and behavior

References:
Bienvenu, T. (2010). L'Endocrâne de Sahelanthropus Tchadensis (Hominidae, Miocène supérieur du Tchad) : reconstitution 3D et morphologie : comparaison avec les hominoïdes actuels et fossiles. Thèse de doctorat en Paléoprimatologie et paléontologie humaine. http://www.theses.fr/2010POIT2301

Brunet, M., Guy, F., Pilbeam, D., et al. (2002). A new hominid from the Upper Miocene of Chad, Central Africa. Nature 418, 145-151. https://doi.org/10.1038/nature00879

Guy, F., Lieberman, D.E., Pilbeam, D., et al. (2005). Morphological affinities of the Sahelanthropus tchadensis (Late Miocene hominid from Chad) cranium. PNAS 102(52), 18836-18841. https://doi.org/10.1073/pnas.0509564102

Haile-Selassie, Y., Melillo, S.M., Vazzana, A., et al. (2019). A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia. Nature 573, 214-219. https://doi.org/10.1038/s41586-019-15...

Zollikofer, C.P.E., Ponce de Leon, M.S., Lieberman, D.E., et al. (2005). Virtual cranial reconstruction of Sahelanthropus tchadensis. Nature 434, 755–759. https://doi.org/10.1038/nature03397

Video material sources:
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Angela Redmon (YouTube)
Octavio Mateus (YouTube)
PLOS Media (YouTube)
SlicerMorph SlicerMorph (YouTube)
Tokyo Zoo (YouTube)
What's in John's Freezer (YouTube)

Narrated by: Miles Wischnewski

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