Paleontology: alongside Lucy, other bipeds ignored?


1976, Laetoli, in the middle of the Tanzanian savannah. In the volcanic tuff, five footprints are found. “Strange” and “Oddly formed”, the large footprints resemble those of an ursid (the bear family) which would move on its two hind legs.

Nearby traces attributed to Lucy’s species

Two years later, the unearth of another set of footprints nearby and identified as belonging to an Australopithecus afarensis, the same species as the famous Lucy, makes you forget the previous traces which are difficult to attribute. Dating the Laetoli site to more than 3.6 million years is boiling: bipedalism dates back to at least this time, long before the increase in brain size in the genus Homo.

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Since then, other discoveries, including that of the man from Toumaï in Chad in 2001, have come to thicken the mystery of the emergence of bipedalism. Hence a renewed interest in the strange footprints of Laetoli, re-examined in 2019.

An international team compared them to those of black bears, chimpanzees and humans. As might be expected, given the lack of ursid fossils in the area, the footprints do not match a bear, their results published on 1er December in the scientific journal Nature.

A slow gait with crossed feet

Closer to those of the chimpanzee or the hominin (a subfamily of Hominidae), these five steps are also different in their morphology from those of an australopithecine. afarensis. If the researchers do not rule out the hypothesis of a young Australopithecus, their analyzes favor the existence of another bipedal species. “The proportions of the foot, the parameters of the gait and the 3D reconstructions of the morphology indicate that two different hominins coexisted in Laetoli, Australopithecus afarensis and another “, describe paleobiologists.

What could this Tanzanian cousin of Ethiopian Lucy look like? With a height of 101 to 104 centimeters, he was slightly smaller. His gait, very slow, was made by crossing one foot in front of the other. Its feet, broad and short, presented an inch more independent than the modern feet. The question of whether this was an exceptional bipedalism remains open. If the existence of this other hominin species was confirmed, it would mean that it cohabited at the same time and on the same places as the australopithecines. afarensis.

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