New fossil discovery of an early human ancestor reveals that it walked upright, just like humans

Paranthropus robustus was a species of prehistoric human that lived in South Africa about 2 million years ago, alongside Homo ergaster, a direct ancestor of modern people. Fossils of Paranthropus robustus are found in abundance at Swartkrans Cave, situated about halfway between Johannesburg and Pretoria. Much has been revealed about the diet and social organization of this extinct species based on studies of its many skulls and hundreds of teeth, which have been recovered from Swartkrans since scientific excavations began there in 1948.

For instance, the extremely heavy jaws and thickly enameled teeth of Paranthropus robustus suggest that, when times were lean, it was capable of subsisting on low-quality foods that were difficult to chew. Moreover, some of the skulls and teeth of Paranthropus robustus are exceptionally large, while others are robust but not as large as those in the first group.

The fossil not only demonstrates that the species was, like modern humans, a habitual upright walker, but also confirms it was also extremely small.

The small size of the new Paranthropus robustus individual would have made it vulnerable to predators—such as sabertooth cats and giant hyenas—known to have occupied the area around Swartkrans Cave. This notion is confirmed by the team’s investigation of damage on the surface of the fossils, which includes tooth marks and other chewing damage identical to that made by leopards on the bones of their prey.