This 2.6-million-year-old jawbone changes the human story

"If we are to understand our own evolutionary trajectory as a genus and species, we need to understand the environmental, ecological, and competitive factors that shaped our evolution," said Alemseged, the Donald N. Pritzker Professor of Organismal Biology and Anatomy at UChicago. "This discovery is so much more than a simple snapshot of Paranthropus' occurrence: It sheds fresh light on the driving forces behind the evolution of the genus."

Why Paranthropus Seemed Absent From the Afar

After the split between human and chimpanzee lineages around 7 million years ago, early human ancestors followed a complex evolutionary path that eventually led to the emergence of Homo sapiens roughly 300,000 years ago.

"We strive to understand who we are and how we became to be human, and that has implications for how we behave and how we are going to impact the environment around us, and how that, in turn, is going to impact us," Alemseged said.

The fossil record includes more than 15 known hominin species, which generally fall into four broad groups:

• Facultative bipeds, e.g. Ardipithecus -- Occasionally bipedal but mostly living in trees and walking on all four limbs.
• Habitual bipeds: Australopithecus -- Retained arboreality to some degree but mostly practiced upright walking and experimented with stone tools.
• Obligate bipeds: Homo -- The genus to which modern humans belong, characterized by a larger brain, sophisticated tools and obligate bipedalism.
• Robust hominins: Paranthropus (also known as robust australopithecines) -- Habitually bipedal like Australopithecus but distinguished by extremely large molars capped by thick enamel and facial and muscular configurations that suggest a powerful chewing apparatus.

According to Alemseged, the lack of Paranthropus fossils in the Afar had long puzzled researchers. "Hundreds of fossils representing over a dozen species of Ardipithecus, Australopithecus, and Homo had been found in the Afar region of northern Ethiopia, so the apparent absence of Paranthropus was conspicuous and puzzling to paleoanthropologists, many of whom had concluded the genus simply never ventured that far north."

Some scientists proposed that Paranthropus was limited by a highly specialized diet, while others suggested it may have failed to compete with the more flexible Homo. Alemseged rejected both ideas. "Neither was the case: Paranthropus was as widespread and versatile as Homo and the new find shows that its absence in the Afar was an artifact of the fossil record."

A Jawbone That Changes the Map of Human Evolution

The newly reported fossil is a partial jaw dating to 2.6 million years ago, recovered from the Mille-Logya research area within the Afar region. It ranks among the oldest Paranthropus specimens ever discovered. After collecting as many fragments as possible at the site, researchers transported the material to Chicago, where they examined its internal structure and shape using high-resolution micro-CT scanning.

"It's a remarkable nexus: an ultra-modern technology being applied to a 2.6-million-year-old fossil to tell a story that is common to us all," Alemseged said.

The evidence shows that Paranthropus was not only widespread but also capable of thriving alongside early members of Homo, rather than being quickly displaced by them.

Rethinking the "Nutcracker" Hominin

Paranthropus has long been labeled the "nutcracker" genus, a nickname inspired by its massive jaws, thick tooth enamel, and oversized molars. These traits led researchers to believe the genus was limited to a narrow, specialized diet. The Afar fossil challenges that assumption, indicating that from its earliest stages, Paranthropus was both adaptable and capable of exploiting a wider range of food sources.

"The new discovery gives us insight into the competitive edges that each group had, the type of diet they were consuming, the type of muscular and skeletal adaptations that they had, whether they were using stone tools or not -- all parts of their adaptation and behavior that we are trying to figure out," Alemseged said. "Discoveries like this really trigger interesting questions in terms of reviewing, revising, and then coming up with new hypotheses as to what the key differences were between the main hominin groups."

Research Oversight and Publication Details

Field research and work conducted at the National Museum of Ethiopia took place with approval from the Ethiopian Heritage Authority of the Ministry of Tourism, along with additional authorization from the Afar Regional State Tourism and Culture Bureau. Funding for the project was provided by Margaret and Will Hearst and the University of Chicago.

The study, titled "First Afar Paranthropus fossil expands the distribution of a versatile genus," was published in Nature in January 2026. The co-authors are Zeresenay Alemseged, Fred Spoor, Denné Reed, W. Andrew Barr, Denis Geraads, René Bobe and Jonathan G. Wynn.