Australian researchers discover two-million-year-old skull of human cousin that sheds light on evolution

Paranthropus robustus

Credit: La Trobe University

Archaeologists exploring a cave system in South Africa have found the well-preserved skull of an ancient human-like creature that roamed the planet at the same time as our director ancestor Homo erectus.

The two-million-year old skull belonged to an adult male Paranthropus robustus, a small-brained member of the human family tree.

The discovery of the skull in the Drimolen cave system near Johannesburg in 2018 contributes to the understanding of human evolution.

The skull, which was painstakingly reconstructed from hundreds of fragments of bone, was found by Australian archeologists from La Trobe University in Melbourne.

Paranthropus robustus existed at the same time as Homo erectus, said palaeoanthropologist Dr Angeline Leece.

“But these two vastly different species – Homo erectus with their relatively large brains and small teeth, and Paranthropus robustus with their relatively large teeth and small brains – represent divergent evolutionary experiments,” she said.

Hominids of the Australopithecus robustus or Paranthropus robustus genus

Credit: DeAgostini/Getty Images

The fact that enough fragments of bone were found to be able to rebuild the skull was extremely rare, she said.

Paranthropus robustus may have died out as climate change produced a wetter environment that impacted their plant-based diet of tubers and roots.

Homo erectus, in contrast, which ate meat as well as plants, survived the changes.  "We believe these changes took place during a time when South Africa was drying out, leading to the extinction of a number of contemporaneous mammal species," said Andy Herries, an archeologist involved in the discovery. "It is likely that climate change produced environmental stressors that drove evolution within Paranthropus robustus."

Fossil discoveries suggest that while Homo erectus was ultimately more successful as a species, Paranthropus robustus was more common but then died out.

The creatures were small — males are thought to have been around 3ft 9in tall and to have weighed 120lbs, while females were 3ft 3in tall and weighed around 90lbs.

The skull was found close to where the skull of a Homo erectus child was discovered five years ago.

The findings were published in the journal Nature, Ecology and Evolution.