The Face of Change

Discovery of new hominid revolutionizes human history

The dental paleoanthropology expert who helped verify the discovery as a new species is now building team to find clues to its habitat, diet.

The plastic baggie crinkles as Luke Delezene pulls out the casts of teeth he hauled back and forth across three continents for two years. To the untrained eye, the pink resin tooth molds look like those of a modern-day teenager.

That’s what makes them so remarkable.

The teeth are part of a major fossil discovery made in 2013 in the Rising Star Cave about 30 miles northwest of Johannesburg, South Africa. Scientists found more than 1,500 fossil remains of an early hominid. Some elements of the fossils seemed modern, like the feet, molar teeth and wrists. But other parts of the anatomy, like fingers, head size and tooth roots, were quite primitive.

Since the discovery, an international team of scientists — including Delezene, assistant professor of anthropology at the University of Arkansas and an expert in hominin dental anatomy — studied the remains to try to verify the species of origin.

“We were all in agreement that the fossils are different than anything found previously,” Delezene said.

National Geographic and NOVA announced the news in September 2015 that Delezene and the rest of the team led by Lee Berger, a National Geographic explorer-in-residence, had identified a new species of human ancestor — Homo naledi. Berger is a former adjunct professor at the University of Arkansas, son of alumni and currently a research professor at the University of Witswatersrand in Johannesburg.

It wasn’t his ties to Arkansas that led Berger to look to the U of A for someone to analyze the teeth from his discovery, however. The university is known for its resident experts on dental paleoanthropology and is home to the largest known collection of tooth casts.

“Historically, teeth are the primary thing people use to identify new species,” Delezene said, holding a 3D printed copy of a lower and partial upper jaw of Homo naledi. “They can tell us about diet, ecology and environment.”

The process of verifying a new species is arduous. For two years, Delezene carried the baggie of tooth molds back and forth from South Africa to England, Kenya and Arkansas while collaborating with an international group of scientists to compare them to all other known hominin teeth with fellow scientist Matt Skinner, research professor at the University of Kent in England.

Delezene and the other researchers who validated the find coauthored one of two papers on the discovery in the journal eLife. The other paper focuses on the geology and location of the find. Delezene and the dental analysis team are working on a suite of more detailed articles about the new species as their research continues.

“We’re trying to determine its ecological space in evolution and how it’s related to other extinct human-like species,” he said. “We want to know what it is, what it was eating, how it was living its life. And teeth can tell us a lot about that.”

They scraped the plaque from the teeth this summer and it is currently being analyzed for dietary clues. Plaque traps some food, and bacteria in the plaque can give information on the environment.

Further work will be done on the chemical isotopes within the teeth that will give even more information about Homo naledi’s diet and life.

Delezene and colleagues are working on grant proposals to expand their team of anthropological dental experts and return to South Africa where the remains are stored to dig deeper into the lives of Homo naledi.

“We have lots to do,” Delezene said. “We just need the time and the money.”