Archaeologists discover the ancient skull of distant human cousin Paranthropus robustus

A two-million-year-old skull of a distant broad-toothed human cousin has been unearthed in an archaeological dig led by Australia deep into a South African cave system.

The discovery is the earliest known and best preserved example of a small-brained hominin called Paranthropus robustus, say researchers from the University of La Trobe.

The nearly complete male skull, found in the Drimolen cave system near Johannesburg in 2018, could also lead to a new understanding of human microevolution.

Paranthropus robustus walked the Earth around the same time as our direct ancestor Homo erectus, paleoanthropologist Angeline Leece said, referring to hominins, a small-brained member of the human family tree.

“But these two very 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,” he said.

“While we were the lineage that eventually won, fossil records suggest two million years ago that Paranthropus robustus was much more common than Homo erectus in the landscape.”

Until recently, scientists believed Paranthropus robustus existed in gorilla-like social structures, with large dominant males living in a group of smaller Paranthropus robustus females.

This rare male fossil is more similar in size to female specimens previously found at the site, providing the first high-resolution evidence for microevolution in early hominid species.

The researchers say this discovery could lead to a revised system for classifying and understanding the paleobiology of human ancestors, a significant development for their field.

Archaeologist Andy Herries said the skull, which was carefully reconstructed from hundreds of pieces of bone, represented the start of a highly successful Paranthropus robustus lineage that has existed in South Africa for a million years.

“We believe these changes occurred during a period when South Africa was drying up, leading to the extinction of a number of contemporary mammal species.

“Climate change is likely to have produced environmental stressors that drove evolution within Paranthropus robustus.”

The results of the new discovery in South Africa’s Cradle of Humankind were published Tuesday in Nature Ecology and Evolution.

AAP