In the News: New Paranthropus Robustus Fossils Discovered in South Africa

Source: 2025. The SWT1/HR-2a hominin left os coxae shown in medial (superior up; anterior right) (A), lateral (superior up; anterior left) (B), and inferior (lateral up; anterior left) (C) views. Bar scale = 1 cm. Journal of Human Evolution. [cited 2025 March] https://www.sciencedirect.com/science/article/pii/S0047248424001556?via%3Dihub

Every so often, a missing piece of time and history’s puzzle is uncovered. To the untrained eye, these shapeless forms may look like nothing more than rocks on the side of the road. This particular discovery warrants more than a cursory glance. Scientists in South Africa have stumbled upon new fossil remains of Paranthropus robustus, a hominin that lived two million years ago.

Paleoanthropologists are no strangers to piecing together a great deal with only a few bones. The initial discovery of Paranthropus robustus was by Robert Broom in 1938. His find was based on nothing more than a jaw and a molar, which didn’t quite align with his understanding of similar species from that time in history. The detention and jaws were significantly larger than the Au. africanus fossils Broom found earlier in his career. After further exploration of the initial excavation site in Kromdraai, South Africa, Broom and his team collected enough bones to confidently name a new member of our family tree—Paranthropus robustus.

Source: The original complete skull (without mandible) of a 1,8 million years old Paranthropus robustus (SK-48 Swartkrans (26°00'S 27°45'E), Gauteng,), discovered in South Africa . Collection of the Transvaal Museum, Northern Flagship Institute, Pretoria South Africa. [cited 2025 March]

Though plenty of craniodental fossils had been collected, postcranial fossils were largely absent—until now. At Swartkrans, a fossil bearing cave in South Africa, scientists have found the first known virtually complete femur and complete tibia, a partial os coxae (hip), and other articulating elements. These findings add to our limited understanding of P. robustus locomotion and posture.

The size and orientation of these lower back and leg fragments indicate two things about P. robustus. First, the species was quite small. According to Professor Pickering from the University of Wisconsin-Madison, P. robustus is almost similar in size to Australopithecus afarensis (‘Lucy’) and Homo floresiensis (‘Hobbit’). The female that was found was only about a meter tall and 27 kg when she died. That’s about as tall as a baseball bat! Scientists believe this female was well-suited for terrestrial bipedalism. Evidence includes a high femoral angle, the stable construction of the ankle, and the presence of a large and capable hip-extending muscle, all of which play a role in stabilization during orthograde and bipedal loading. The crural index, or the ratio of the length of the lower leg to the length of the thigh, aligns precisely with those of humans and gorillas. Despite this, climbing behavior cannot yet be ruled out.

These bones, though damaged and sparse, support our understanding of our human past and Paranthropus robustus’ role in evolutionary history. Explorations in the cradle of humankind are ongoing and promising.