Sahelanthropus, the oldest representative of man, is indeed a biped...but that's not all!

Sahelanthropus, the oldest representative of humans, is indeed a biped

Left: 3D model of the postcranial material of Sahelanthropus tchadensis. From left to right: femur, posterior and medial views; left and right ulna, anterior and lateral views. Right: An example of an analysis performed to explain movement patterns in Sahelanthropus tchadensis. (From left to right) 3D maps of cortical thickness changes in the femur of Sahel, extant humans, chimpanzees, and gorillas (posterior view). This analysis allowed us to understand changes in mechanical constraints on the femur and interpret these constraints in terms of motion patterns.Image credit: © Franck Guy / PALEVOPRIM / CNRS – University of Poitiers

The acquisition of bipedalism is considered a decisive step in human evolution. However, there is no consensus on its morphology and age, especially due to the lack of fossil remains. A team of researchers from CNRS, the University of Poitiers and their partners in Chad examined three limb bones from the oldest human representative identified so far, Sahelanthropus tchadensis.published in nature Aug. 24, 2022 This study reinforces the idea that bipedalism was acquired very early in our history, when it was still associated with the ability to move on all fours in trees.


Sahelanthropus tchadensis is 7 million years old and is considered to be the oldest representative species of humans. Its description dates back to 2001, when the French-Chad Paleoanthropological Survey (MPFT) discovered several human remains, including a well-preserved skull, in Toros-Menalla, Djurab Desert (Chad). This skull, particularly the orientation and anterior position of the occipital foramen that inserts into the spine, indicates the way the two legs move, suggesting that it was capable of bipedal walking.

The location of Toros-Menalla 266 (TM 266) yielded two ulna (forearm bones) and one femur (thighbone), in addition to the skull nicknamed Toumaï and the published fragments of jaws and teeth. The bones have also been attributed to the Sahel, as no other large primates have been found at the site; however, it is impossible to know if they belonged to the same person as the skull.Paleontologists from the University of Poitiers, CNRS, N’Djamena University and the National Centre for Development Research (CNRD, Chad) nature August 24, 2022.

  • Sahelanthropus, the oldest representative of man, is indeed a biped...but that's not all!

    Franck GUY (left) and Guillaume DAVER (right) at the collection work meeting at the PALEVOPRIM laboratory in Poitiers (CNRS/University of Poitiers).Image credit: © Franck Guy / PALEVOPRIM / CNRS – University of Poitiers

  • Sahelanthropus, the oldest representative of man, is indeed a biped...but that's not all!

    Representation of movement patterns practiced by Sahelanthropus. Bipedalism was common among the earliest known human representatives, either on the ground or in trees. It coexists with other types of locomotion in arboreal environments, including quadrupedal locomotion using a firm hand grip, and is markedly different from locomotion in gorillas and chimpanzees that use the back of the phalanges as support (“knuckle walking”).Image credit: © Sabine Riffaut, Guillaume Daver, Franck Guy / PALEVOPRIM / CNRS – University of Poitiers

A series of measurements and analyses of the femur and ulna were performed using microtomography, including their external morphology and internal structure: biometrics, geometric morphometrics, biomechanical indicators, etc. These data were compared with relatively large samples of living and fossil great apes: chimpanzees, gorillas, orangutans, Miocene apes and members of human groups (Orrorin, Ardipithecus, Australopithecus, Homo sapiens, Homo sapiens).

The structure of the femur suggests that the Sahel were usually bipedal on the ground, but may also be in trees. According to the results from the ulna, this bipedalism coexists with a form of quadrupedal walking in an arboreal environment, namely arboreal climbing with firm hand grip, which is markedly different from gorillas and chimpanzees who lean on the back of the phalanges.

  • Sahelanthropus, the oldest representative of man, is indeed a biped...but that's not all!

    The Chulab Desert, where the fossil site of the postcranial remains of the Sahel Chad Shah was unearthed.Image credit: © MPFT, PALEVOPRIM / CNRS – University of Poitiers

  • Sahelanthropus, the oldest representative of man, is indeed a biped...but that's not all!

    Humans split from the chimpanzee population in the most recent Miocene, likely between 10 and 7 million years ago. This difference leads to very different morphologies: for example, differences in the skeleton of the limbs correlate significantly with quadrupedal locomotion in chimpanzees and bipedal locomotion in extant humans.Image credit: © Franck Guy / PALEVOPRIM / CNRS – University of Poitiers

The conclusions of this study, including the identification of habitual bipedal walking, are based on the observation and comparison of more than two dozen features of the femur and ulna. They are by far the most concise explanations of these feature combinations. All of these data reinforce the concept of bipedal locomotion very early in human history, even as other modes of movement were practiced at this stage.


Study of part of left femur suggests Sahelanthropus tchadensis isn’t human after all


More information:
Franck Guy, Postcranial Evidence for Bipedal Walking in Late Miocene Homo sapiens from Chad, nature (2022). DOI: 10.1038/s41586-022-04901-z. www.nature.com/articles/s41586-022-04901-z

To stand up for the earliest bipedal humans, nature (2022). DOI: 10.1038/d41586-022-02226-5

Citation: Sahelanthropus, Oldest Representative of Humans, Bipedal indeed (24 Aug 2022) Retrieved 24 Aug 2022 from https://phys.org/news/2022-08-sahelanthropus-oldest-humanity -bipedal.html

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