7 Million Years Old – New Secrets of the Oldest Representative of Humanity Revealed

The oldest representative species of humanity, Sahelanthropus tchadensis, was bipedal, according to a recent study.

Bipedalism is thought to have been the tipping point in human evolution. Although there are no fossilized remains, there is controversy on its methods and age. Three limb bones from Sahelanthropus tchadensis, the earliest known member of the human genus, were examined by scientists from the University of Poitiers, the French National Centre for Scientific Research (CNRS), and its collaborators in Chad. The study, which was just published in the journal Nature, lends support to the idea that bipedalism emerged very early in the history of humanity, when it was still thought that people could only travel on four limbs in trees.

At the PALEVOPRIM laboratory in Poitiers (CNRS/University of Poitiers), Franck Guy (left) and Guillaume Daver (right) are working on a collection. Franck Guy is to be credited with Paleoprim, CNRS, and the University of Poitiers.

With a 7 million-year age, Sahelanthropus tchadensis is regarded as the earliest representative species of humans. The bones of three humans, including one with an especially well-preserved cranium, were discovered near Toros-Menalla in the Djurab Desert (Chad) in 2001 by the Franco-Chadian Paleoanthropological Mission (MPFT). This skull shows evidence of two-legged mobility, suggesting that it was capable of bipedalism. This is especially true of the orientation and anterior location of the occipital foramen, where the spinal column is inserted.

The Toros-Menalla 266 (TM 266) site also produced two ulnae (forearm bones) and a femur in addition to the skull known as Touma and the jaw and tooth fragments that have already been reported (thigh bone). Because no other large primate was discovered at the location, these bones were also assigned to Sahelanthropus; however, it is impossible to tell if they come from the same person as the cranium. The whole analysis was recently published in Nature by paleontologists from the University of Poitiers, the CNRS, the University of N'Djamena, and the National Centre of Research for Development (CNRD, Chad).                                                                                                                     3D representations of Sahelanthropus tchadensis' postcranial bones. The right and left ulnae, in anterior and lateral view, and the femur, in posterior and medial view, are shown from left to right. Right: An illustration of a study done to interpret Sahelanthropus tchadensis's manner of locomotion. Sahelanthropus, a living human, a chimpanzee, and a gorilla are shown in the order of left to right on the 3D cortical thickness variation map for their femurs (in posterior view). We may interpret these restrictions in terms of locomotor mode thanks to our approach, which helps us understand how mechanical constraints on the femur vary. Franck Guy is to be credited with Paleoprim, CNRS, and the University of Poitiers.

Using microtomography imaging, a variety of measures and analyses were performed on the femur and ulnae to examine both their exterior morphology and interior structures. These included biometric measurements, geometric morphometrics, biomechanical indicators, etc. These findings were contrasted with those of a sizable sample of living and extinct apes, including chimpanzees, gorillas, orangutans, Miocene apes, and humans (Orrorin, Ardipithecus, australopithecines, ancient Homo, Homo sapiens).

Sahelanthropus was likely bipedal in trees as well as on the ground, according to the femur's anatomy. Results from the ulnae indicate that this bipedalism coexisted in arboreal habitats with a type of quadrupedalism, or arboreal clambering made possible by firm hand grips, which is obviously distinct from that of gorillas and chimpanzees who rest on the rear of their phalanges.

The fossil sites that produced Sahelanthropus tchadensis' postcranial bones are found in the Djurab Desert. University of Poitiers / CNRS / MPFT, PALEVOPRIM

The observations and comparisons of more than twenty features of the femur and ulnae formed the basis for this study's conclusions, which included the identification of habitual bipedalism. They are by far the most frugal interpretation of these characteristics combined. Even though other kinds of mobility were also used at this time, all of these facts support the idea of extremely early bipedal locomotion in human history.

The French Ministry of Europe and Foreign Affairs, the Chadian Government, the CNRS, the Nouvelle-Aquitaine Region, the University of Poitiers, and the French representative in Chad all provided funding for this project. It is dedicated to the late Yves Coppens, who started the MPFT's work in the Djourab Desert and served as its inspiration.

Postcranial evidence of late Miocene hominid bipedalism was discovered in Chad, according to a study published in Nature on August 24 by G. Daver, F. Guy, H. T. Mackaye, A. Likius, J. -R. Boisserie, A. Moussa, L. Pallas, P. Vignaud, and N. D. Clarisse.

The Région Nouvelle-Aquitaine, Université de Poitiers, and the Centre National de la Recherche Scientifique all provided funding for the study.                                        

By CNRS