Representation of the modes of locomotion practiced by Sahelanthropus. Bipedalism was common among the earliest recognized agents of humankind, probably on the ground but also in trees. It existed side-by-side with other kinds of movement in a tree environment, including quadrupedal motion utilizing firm hand grips, clearly differing from that of gorillas and chimpanzees who use the back of their phalanges for assistance (” knuckle-walking”). Credit: Sabine Riffaut, Guillaume Daver, Franck Guy/ PALEVOPRIM/ CNRS– University of Poitiers
A new study reveals that Sahelanthropus tchadensis, the oldest representative types of humankind, was bipedal.
It is thought that the development of bipedalism was a turning point in human development. There is difference over its modalities and age, especially due to the reality there are no fossilized remains. Researchers from the University of Poitiers, the French National Centre for Scientific Research (CNRS), and its Chadian partners analyzed 3 limb bones from Sahelanthropus tchadensis, the earliest known representative of the human genus. The research study, which was just recently released in the journal Nature, supports the hypothesis that bipedalism was developed exceptionally early in human history, at a time still associated with the capability to proceed 4 limbs in trees.
Collection working session in between Franck Guy (left) and Guillaume Daver (best), at the PALEVOPRIM laboratory, Poitiers (CNRS/University of Poitiers). Credit: Franck Guy/ PALEVOPRIM/ CNRS– University of Poitiers
Sahelanthropus tchadensis is considered the earliest representative species of people, going back 7 million years. Its description goes back to 2001 when the Franco-Chadian Paleoanthropological Mission (MPFT) discovered the bones of 3 individuals at Toros-Menalla in the Djurab Desert (Chad), consisting of an especially unspoiled cranium. This cranium, especially the orientation and anterior place of the occipital foramen where the spine is placed, reveals a kind of mobility on 2 legs, implying that it can bipedalism.
In addition to the cranium, nicknamed Toumaï, and fragments of jaws and teeth that have already been released, the locality of Toros-Menalla 266 (TM 266) yielded two ulnae (forearm bone) and a thigh (thigh bone). These bones were likewise credited to Sahelanthropus due to the fact that no other large primate was found at the site; nevertheless, it is difficult to know if they belong to the very same person as the cranium. Paleontologists from the University of Poitiers, the CNRS, the University of NDjamena, and the National Centre of Research for Development (CNRD, Chad) recently published their total analysis in Nature.
Credit: Sabine Riffaut, Guillaume Daver, Franck Guy/ PALEVOPRIM/ CNRS– University of Poitiers
Scientists from the University of Poitiers, the French National Centre for Scientific Research (CNRS), and its Chadian partners examined three limb bones from Sahelanthropus tchadensis, the earliest recognized agent of the human genus. Paleontologists from the University of Poitiers, the CNRS, the University of NDjamena, and the National Centre of Research for Development (CNRD, Chad) just recently published their complete analysis in Nature.
: Example of analysis carried out to translate the locomotor mode of Sahelanthropus tchadensis. 3D cortical thickness variation map for the femurs of (from left to right) Sahelanthropus, an extant human, a chimpanzee, and a gorilla (in posterior view). Credit: Franck Guy/ PALEVOPRIM/ CNRS– University of Poitiers
The thigh and ulnae were subjected to a battery of measurements and analyses, worrying both their external morphology and their internal structures using microtomography imaging: biometric measurements, geometric morphometrics, biomechanical signs, etc. These information were compared to those of a relatively large sample of extant and fossil apes: chimpanzees, gorillas, orangutans, Miocene apes, and members of the human group (Orrorin, Ardipithecus, australopithecines, ancient Homo, Homo sapiens).
The structure of the thigh suggests that Sahelanthropus was usually bipedal on the ground, however probably also in trees. According to arise from the ulnae, this bipedalism existed together in arboreal environments with a type of quadrupedalism, that is arboreal climbing made it possible for by firm hand grips, plainly varying from that of gorillas and chimpanzees who lean on the back of their phalanges.
The Djurab Desert, where the fossil websites that yielded the postcranial remains of Sahelanthropus tchadensis lie. Credit: MPFT, PALEVOPRIM/ CNRS– University of Poitiers
The conclusions of this study, consisting of the recognition of habitual bipedalism, are based on the observation and comparison of more than twenty qualities of the femur and ulnae. They are, by far, the most parsimonious analysis of the mix of these qualities. All these data reinforce the concept of extremely early bipedal locomotion in human history, even if at this phase other modes of mobility were also practiced.
This work was supported by the French Ministry for Europe and Foreign Affairs, the Chadian Government, the French National Research Agency (ANR), the Nouvelle-Aquitaine Region, the CNRS, the University of Poitiers and the French representation in Chad. It is devoted to the memory of the late Yves Coppens, precursor and inspirer of the MPFTs operate in the Djourab Desert.
Referral: “Postcranial evidence of late Miocene hominin bipedalism in Chad” by G. Daver, F. Guy, H. T. Mackaye, A. Likius, J. -R. Boisserie, A. Moussa, L. Pallas, P. Vignaud, and N. D. Clarisse, 24 August 2022, Nature.DOI: 10.1038/ s41586-022-04901-z.
The study was funded by the Région Nouvelle-Aquitaine, Université de Poitiers, and the Centre National de la Recherche Scientifique..
3D cortical thickness variation map for the thighs of (from left to right) Sahelanthropus, an extant human, a chimpanzee, and a gorilla (in posterior view). Credit: Franck Guy/ PALEVOPRIM/ CNRS– University of Poitiers
