Aug. 24 () –
The modalities and the date of appearance of bipedalism continue to be the subject of debate, in particular due to a small number of very old human fossils. The Sahelanthropus tchadensisdiscovered in 2001 in Chad, is considered the oldest representative of humanity and a new study, published in the journal ‘Nature’, confirms that it was bipedal.
The research highlights that the shape of his skull suggests a bipedal station Y his description of three limb bones of Sahelanthropus confirms the usual but not exclusive bipedalism.
The acquisition of bipedalism is considered a decisive step in human evolution. The research team, which includes researchers from the National Center for Scientific Research (CNRS) and the University of Poitiers, in France, together with paleontologists from the University of N’Djamena and the National Research Center for Development, in Chad, has examined three limb bones from the oldest currently identified human representative, Sahelanthropus tchadensis.
This study reinforces the idea that bipedalism was acquired very early in our history, at a time still associated with the ability to move on four limbs in trees.
At 7 million years old, Sahelanthropus tchadensis is considered the oldest representative species of humanity. Its description dates back to 2001, when the Franco-Chadian Paleoanthropological Mission (MPFT) discovered in Toros-Menalla, in the Djurab desert (Chad), the remains of several individuals, including a very well-preserved skull.
This skull, and in particular the orientation and anterior position of the occipital foramen where the spinal column inserts, indicates a mode of locomotion on two legs, suggesting that it was capable of being bipedal.
In addition to the skull, nicknamed Toumaï, and the previously published jaw and tooth fragments, two ulnae (forearm bone) and a femur (thigh bone) were found at the Toros-Menalla 266 (TM 266) locality. These bones were also attributed to Sahelanthropus because no other large primate was found at the site; however, it is impossible to know if they belong to the same individual as the skull.
The femur and ulna were subjected to a battery of measurements and analyses, related to both their external morphology and their internal structures using microtomography images: biometric measurements, geometric morphometry, biomechanical indicators, etc. These data are
compared with 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 femur indicates that Sahelanthropus used to be bipedal on the ground, but probably also in the trees.. According to the results of the cubits, this bipedalism coexisted in arboreal environments with a form of quadrupedalism, that is, tree climbing made possible by the firm grip of the hands, clearly different from that of gorillas and chimpanzees that lean on the back of their hands. their phalanges.
The conclusions of this study, including the identification of habitual bipedalism, are based on the observation and comparison of more than twenty features of the femur and ulnae. They are by far the most parsimonious interpretation of the combination of these traits. All these data reinforce the concept of bipedal locomotion very early in human history, although other modes of locomotion were also practiced at this stage.
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