By Maina Kiarie
Sahelanthropus tchadensis lived sometime between 7 and 6 million years ago in West-Central Africa (Chad) and is one of the oldest known species on the human family tree. The fossil nicknamed Toumaï (“hope of life” in the local Dazaga language)was discovered in 2001 by a team led by French paleontologist Michael Brunet, in northern Chad. The discovery of Sahelanthropus fossils shows that the earliest humans were more widely distributed. Previously it was thought that the earliest humans were spread along the African Rift Valley.
Sahelanthropus is seen to have had a combination of human and ape features. A small brain (about 320cc – 380cc, like a chimpanzees), very prominent brow ridges, an elongated skull and sloping face made Sahelanthropus ape-like. Their human-like features are; small canine teeth, a short middle part of the face and a foramen magnum (the spinal cord opening on the occipital bone) which is beneath the skull instead of towards the back like in other non-bipedal apes. The position of the foramen magnum in Sahelanthropus is similar to the upright walking humans. Being able to walk upright helped Sahelanthropus survive in diverse habitats like forests and grasslands.
It is not yet known how big this species was as only cranial (head) bones have been found to date. Similarly, since there have not yet been studies of its teeth, scientists have not been specific about its diet. However, based on its environment and other early human species, it can be assumed that it ate a mainly plant-based diet including leaves, fruit, seed, roots, nuts and also insects.
There are still many questions about Toumai and some scientists are even doubtful that it walked on two legs (bipedal). Why did Sahelanthropus have small canines compared to chimpanzees and many other primates (the long canines are used to threaten others, especially when competing for mates)? Is Sahelanthropus tchadensis a common ancestor of humans and chimpanzees? A new generation of scientists will grapple with these and other questions for several years to come.