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Le fémur de S. tchadensis.

Walking on two legs is at least seven million years old

What link can be proven between these remains and Toma’s skull?

Frank Jay: Like the skull, these bones belong to the lineage that gave rise to modern humans, hominins. The probability of having multiple hominin species in the same locus – called TM266 – is extremely low. So we think the most plausible is that all of these bones belong to the same species. Sahelanthropus tchadensisthat Thomas, but they represent at least three different individuals.

What features of the femur and ulna indicate bipedalism?

William Daffer: Our interpretation of femur morphology S. chadensis It is based on 16 characters and multiple analyzes of its structure, as well as statistical comparisons of geometric characters. It is clear from the latter that the femur is located in the morphological space of hominins – OrorinAnd the ArdipithecusAnd the AustralopithecusAnd the to turn down -, but beyond the scope of other ancient and current great apes. The same for the ulna. In the end, the femur and ulna bones discovered at the TM266 site were shown to resemble the same bones of the bipedal forms of our lineage.

The femur suggests walking on two legs, usually S. chadensis, that is, a distinct mode of movement on two legs; By comparison, a chimpanzee is essentially four-legged, although it can occasionally walk on two legs: it advances on its feet and hands by resting its second phalanges on the ground, which is called knuckle walking.

How does walking on two legs compare? S. chadensis For those of Ardipithecines, Australopithecines, chimpanzees and modern humans?

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FG: hard to say because the coast , Ardipithecus Other archaic hominins evolved in similar but not identical living environments: these forms shared two-legged walking on the ground which was undoubtedly combined with arboreal behaviours. However, even if millions of years of evolution separate them, bipedal walking for all (pre) humans is adaptive, meaning that our skeletons, muscles, and physiology reflect an adaptation to bipedal locomotion…Chimpanzees and most other primates that He can sometimes walk on two legs and does not show this kind of adaptation to the usual bipedal walk. Thus, at this point in thoughts, it is this skeleton adapted to walking on two legs that characterizes our group, and not just the possibility of moving on two legs.

Is the exploitation of a territory that mixes forests, savannahs and bodies of water the origin of walking on two legs?

GD: in part. The first walking on two legs is the one that is practiced in trees. The extension of land exploitation to the ground can be one of the important stages in the evolution of our movement. Chimpanzees, if they can occasionally descend on the ground, are above all arboreal, omnivores like us, but mostly herbivores and even carnivores. As soon as the former humans began searching for their resources on Earth, the tendency to exploit an ever larger area began. It can only lead to selective pressure in favor of increasingly bipedal walking. Tomai tells us that this process actually began seven million years ago.