Fossil footprints discovered in Kenya reveal that at least eight Paranthropus boisei walked together along the edge of a lake about 1.43 million years ago. Some tracks indicate a stature reaching up to 1.80 m, higher than the estimates generally associated with this species.
Paranthropus boisei belongs to an extinct branch of the human family. This species is known mainly from particularly robust skulls, teeth and jaws. Bones from the rest of the body are rare, which until now limited estimates of its size.
Researcher Kevin Hatala studies fossilized footprints in the sediments.
The tracks studied come from the GaJi10 site, in the Koobi Fora formation, near Lake Turkana. They had been spotted in 1978, then protected under sediment. New excavation and recent analytical methods have made it possible to document them with greater precision.
The researchers compared the shape of the footprints, their orientation and the way the foot hit the ground. These characteristics match Paranthropus better than Homo erectus, another species present in the region. The attribution nevertheless remains based on the morphology of the tracks, for lack of a directly associated skeleton.
Twenty-one footprints appear to have been left by eight individuals moving across the same surface. Their proximity indicates that they were moving together. Most would have been adults, probably males, according to the size of the tracks and comparisons made with modern primates.
The largest footprints correspond to an estimated mass of around 75 kg and therefore a height close to 1.80 m. Paranthropus boisei could therefore have reached dimensions comparable to those of Homo erectus. This observation changes the image of a hominin that was systematically smaller and stockier.
The authors suggest a possible group of males, comparable to certain organizations observed in primates. This interpretation remains cautious, because the footprints capture a unique moment. Other lines of investigation will have to confirm whether this collective movement reflected a regular social structure or an exceptional situation.