Oldest Human Ancestor Fossil Found in Ethiopia—2.8 Million Years Old

Close-up view of the Ledi-Geraru partial mandible close to where it was sighted, known as LD 350-1. (Image: Kaye Reed)
Close-up view of the Ledi-Geraru partial mandible close to where it was sighted, known as LD 350-1. (Image: Kaye Reed)

Researchers have found a human fossil in Ethiopia that is around 2.8 million years old. This is about 400,000 years older than the earliest known specimens on the Homo lineage. The find consists of a lower jaw bone and five teeth.The fossil, known as LD 350-1, was found by Chalachew Seyoum, an Ethiopian national on the team, at the Ledi-Geraru research area in the Afar region of Ethiopia.

Site, geography, and geological stratification where the fossil jaw (designated LD 350-1) was discovered.  Credit: Villmoare, et al.

Site, geography, and geological stratification where the fossil jaw, designated LD 350-1, was discovered. (Image: Villmoare, et al)

“One hill was particularly rich in fossils; it was probably a bend in a stream, where bones tended to gather after animals died,” research team co-leader and study co-author Brian Villmoare said.

We found this fossil coming out of that hill.

sieving-ledi-geraru

Scientists sieve through sand at the Ledi-Geraru site where they discovered the Homo mandible, known as LD 350-1. (Image: Brian Villmoare)

“There is a big gap in the fossil record between about 2.5 million and 3 million years ago—there’s virtually nothing relating to the ancestors of Homo from that time period, in spite of a lot of people looking,” Villmoare, a paleoanthropologist at the University of Nevada in Las Vegas, told Live Science. “Now we have a fossil of Homo from this time, the earliest evidence of Homo yet.

Close-up images of the Ledi-Geraru partial mandible, as seen from different angles and perspectives. Credit: William Kimbel

Close-up images of the Ledi-Geraru partial mandible, as seen from different angles and perspectives. (Image: William Kimbel)

The US-led research team believes the individual lived here when the now parched landscape was open grassland and shrubs nourished by tree-lined rivers and wetlands.

“This is the first inkling we have of that transition to modern behavior. We were no longer solving problems with our bodies, but with our brains,” said Villmoare. Researchers suspect a dramatic change in the environment transformed the landscape of eastern Africa. “It could be that there was some sort of ecological shift, and humans had to evolve or go extinct,” said Villmoare.

A caravan moves across the Lee Adoyta region in the Ledi-Geraru project area near the early Homo site. The hills behind the camels expose sediments that are younger than 2.67 million year old, providing a minimum age for the mandible.  Credit Erin DiMaggio

A caravan moves across the Lee Adoyta region in the Ledi-Geraru project area near the early Homo site. The hills behind the camels expose sediments that are younger than 2.67 million year old, providing a minimum age for the mandible. (Image: Erin DiMaggio)

Other fossils that were recovered nearby the new human remains suggest that the region was much wetter than Hadar, where Lucy was found. Remnants of antelopes, prehistoric elephants, primitive hippos, crocodiles, and fish were all recovered from the Ledi-Geraru site, researchers said. Details of the discoveries are reported in two papers published in Science, reported The Guardian.

Villamoare recalled the moment of discovery. “I heard people yelling Brian! Brian! And I went round the corner, and there was Chalachew. He recognized it, and said: ‘We’ve got a human.’ It had eroded out of the stratigraphy. It was in two pieces and was missing some of the teeth, but it was clearly of the genus Homo.”

Geologists Dr. Erin DiMaggio of Penn State (left) and Dominique Garello (ASU, right) sample a volcanic tuff near the early Homo site in the Ledi-Geraru project area.  Credit J. Ramón Arrowsmith

Geologists Dr. Erin DiMaggio of Penn State (L) and Dominique Garello (ASU, R) sample a volcanic tuff near the early Homo site in the Ledi-Geraru project area. (Image: J. Ramón Arrowsmith)

There is a separate paper published in NatureFred Spoor at University College, London, reports a virtual reconstruction of a Homo habilis skull. “By digitally exploring what Homo habilis really looked like, we could infer the nature of its ancestor, but no such fossils were known,” said Spoor. “Now the Ledi-Geraru jaw has turned up as if on request, suggesting a plausible evolutionary link between Australopithecus afarensis and Homo habilis.”

Without more remains, the mystery still exists. The U.S.-led team has been back to where they found the fossil, but Villamoare said he cannot yet talk about what they did or did not find.

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