Researchers have uncovered tooth fossils in Ethiopia dating back approximately 2.65 million years, belonging to a previously unknown species in the human evolutionary lineage. Remarkably, this species lived alongside the earliest-known members of the genus Homo, which includes modern humans.
Image used for illustrative purposes: Ledi-Geraru paleoanthropological research area/Ji-Elle/Wikimedia Commons
The discovery occurred in the Ledi-Geraru research project area of northeastern Ethiopia’s Afar Region. Scientists found 10 teeth — six molars, two incisors, one premolar, and one canine — from two individuals. Based on their features, the team concluded they belonged to a new species of Australopithecus, as reported by TimesLive.
Until now, six species of Australopithecus, early human ancestors showing a mix of ape-like and human-like traits, were known from fossil sites across Africa. Researchers say the newly discovered teeth exhibit traits that suggest a seventh species existed.
A genus is a group of closely related species with shared characteristics. For example, lions and tigers belong to the same genus but are different species.
Earliest homo species teeth found nearby
In addition, the team uncovered three teeth dating to 2.59 million years ago that display traits of the oldest-known Homo species, first identified from a jawbone found in the same area in 2013.
Because the fossil evidence is incomplete, scientists have not yet formally named either the Australopithecus or Homo species represented by these 13 teeth. Modern humans, Homo sapiens, appeared roughly 300,000 years ago in Africa before spreading worldwide.
Insights into coexistence and competition
These dental fossils provide a window into a poorly understood period in human evolution. Their close age suggests that the new Australopithecus species coexisted with early Homo, raising questions about whether they competed for the same resources.
The teeth also indicate that four hominin species lived in East Africa at the time. Previous fossils show another Australopithecus species and a Paranthropus species, a hominin with a skull adapted for heavy chewing, inhabited East Africa. Another Australopithecus species lived in Southern Africa, bringing the total number of contemporaneous hominins on the continent to five.
“This reinforces the idea that the story of human evolution is not of a single lineage changing slowly through time,” said University of Nevada, Las Vegas palaeoanthropologist Brian Villmoare, lead author of the research published Wednesday in the journal Nature.
“Rather, the pattern of human evolution is similar to that of other organisms, repeatedly branching into multiple species throughout the fossil record, many of whom lived at the same time,” Villmoare added.
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Investigating diet and resource use
Researchers are exploring possible interactions between the Australopithecus and Homo species.
“We are analysing teeth to see if we can tell if they ate the same thing,” said Arizona State University paleoecologist and project co-director Kaye Reed.
If their diets overlapped, the species may have competed for resources, Reed noted. Crude stone tools from the same period were previously discovered nearby, likely made by the Homo species.
Dating the fossils
The age of the teeth was determined using a method that dates feldspar crystals in volcanic ash, measuring the radioactive decay of argon.
Ancient afar: A Lush Landscape
Today, the Afar region is one of Earth’s hottest and lowest areas, characterized by arid badlands. During the time of these species, however, rivers flowed into shallow lakes amid a vegetated landscape, home to giraffes, horses, pigs, elephants, hippos, and antelopes, along with predators such as sabre-toothed cats and hyenas.
Homo is generally believed to have descended from an Australopithecus species, though the exact lineage and timing remain debated. Australopithecus eventually became extinct.
This genus includes the famous fossil Lucy, a member of Australopithecus afarensis who lived about 3.18 million years ago and was discovered in 1974 in the Afar Region. The newly found teeth show traits that distinguish them from Lucy’s species.
“This new Australopithecus species is in no way some ‘missing link,’ and we actually don’t think that it was necessarily ancestral to any known species,” Villmoare said.
“Species arose and many went extinct,” Reed added. “Each find is a piece of the puzzle that puts human evolution into a twiggy tree, rather than a linear graphic.”
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