Fossilized Teeth Might Belong to a Newly Discovered Species of Early Hominins

In Ethiopia, 13 human teeth have been found within volcanic ash layers dating between 26 to 2.8 million years ago. Researchers indicate that some of these teeth are attributed to the genus Homo, hinting that others may belong to a newly identified human lineage, suggesting a coexistence of both species.

“They shared resources and everything was fine,” says Kay Reed from Arizona State University. “I cannot be certain at this point.”

Previous finds suggested that early members of several Homo species existed in this region about 3 million years ago, including Australopithecus afarensis, the species of the well-known Lucy Fossil.

The emergence of the first representatives of the genus Homo around 2.5 million years ago showcases characteristics increasingly reminiscent of modern human traits. So, what unfolded during that period? To delve into this, Reid and her colleagues have been excavating at Ledi-Geraru, an area rich with volcanic deposits from this pivotal epoch.

In 2013, her team unearthed a chin from a 2.8 million-year-old Homo species, pushing back the timeline for the origin of this genus. Recently, her team identified 13 teeth across three distinct layers of ash.

The oldest and youngest dental specimens (dated 2.79 and 2.59 million years) also belong to the genus Homo, as per the team’s findings. Nevertheless, they postulate that the teeth from the middle layer (dated 2.63 million years) are from Australopithecus. All excavation sites are within a kilometer of one another.

“We anticipated discovering more Homo specimens, yet we also encountered Australopithecus,” Reid remarks.

Moreover, Australopithecus teeth exhibit distinctive features when compared to A. afarensis and other members of the genus, leading the team to speculate that they may belong to a new species. If this hypothesis holds, it indicates a more intricate and expansive evolutionary tree leading to modern humans than previously assumed.

“This is a significant finding,” states John Hawks from the University of Wisconsin-Madison. However, he cautions against drawing firm conclusions based merely on a handful of teeth.

“When fossils span a timeframe of 200,000 years, as these teeth do, it’s challenging to assert that they coexisted,” remarks Hawks. “That’s a vast period.”

There are also concerns about the identification of distinct species from these teeth. “Many fossils exhibit characteristics that overlap with various species. It’s feasible to categorize smaller samples into distinct groups—some resembling Homo and others more akin to Australopithecus,” Hawks explains.

“The issue remains statistical; the measurements do not indicate that these teeth are substantially different. They fall within the overlapping size ranges of early Australopithecus and early Homo species.”

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