Researchers Discover Fossilized Teeth That May Have Come From an Unknown Hominin Species
The find suggests that as many as four different hominin lineages lived in eastern Africa between 2.5 million and 3 million years ago
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Modern humans, technically called Homo sapiens, are the only surviving species of the genus Homo, which also includes extinct close cousins such as Homo neanderthalensis and Homo erectus. The oldest Homo fossil remains date back to between around two million and three million years ago, which is the same time period during which Australopithecus afarensis, a potential ancestor of Homo, vanishes. Unfortunately, it’s also a time period with an incomplete fossil record, leaving many questions unanswered about the origin of our genus and its contemporaries.
“You’ve got a more or less 500,000-year gap in the record,” Jessica Thompson, a paleoanthropologist at Yale University who was not involved in the study, tells Science’s Bridget Alex. “All you know is, at the end of it, we’ve got Homo and Australopithecus is mostly gone. Something interesting happened in that window.”
Now, an international team of researchers working in Ethiopia’s Afar Region has discovered hominin fossils from exactly that time period: teeth between 2.6 million and 3 million years old. Hominin refers to a broader group of humans and close human ancestors that includes the genera Homo, Australopithecus, Paranthropus and Ardipithecus. If the researchers’ identification of the fossils is true, they include the oldest known Homo remains, from 2.8 million years ago, as well as evidence of Homo overlapping with Australopithecus at the site 2.6 million years ago.
“They either shared resources, and everything was hunky-dory, or maybe one of them was marginalized,” Kaye Reed, a co-author of the study published last week in Nature and a paleoecologist at Arizona State University, tells New Scientist’s Michael Le Page. “We just don’t know at this point.”
The Australopithecus teeth are significantly different from those of A. afarensis and A. garhi, whose remains researchers had already discovered in the area. If Australopithecus sounds familiar, you’re probably thinking of Lucy, a now-famous A. afarensis who lived sometime between 3 million and 3.7 million years ago and whose remains were found nearby.
“It doesn't match any of these, so it could be a new species," Reed says to Live Science’s Olivia Ferrari. Nevertheless, Reed and her colleagues haven’t yet named it as a new species, since the teeth don’t feature particularly unique aspects, per Live Science. They also haven’t named the early Homo species.
More broadly, this means that at least four different hominins existed in eastern Africa between 2.5 million and 3.0 million years ago: “early Homo, Paranthropus, A. garhi, and the newly discovered Ledi-Geraru Australopithecus,” the researchers outline in the study. Ledi-Geraru is the name of the site where the recent findings were recovered.
University of Chicago paleoanthropologist Zeray Alemseged, however, who wasn’t involved in the research, emphasizes something that the study co-authors also acknowledge, per Science: that the Australopithecus remains could be those of a later version of A. afarensis.
Nevertheless, the overlap "reinforces the idea that the story of human evolution is not of a single lineage changing slowly through time," Brian Villmoare, lead author of the research and a paleoanthropologist at the University of Nevada, Las Vegas, tells Reuters’ Will Dunham. "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.”
The study, however, might raise more questions than it answers. For example, how did the hominins impact each other and divide resources? According to a University of Arkansas statement, competition within this context may have contributed to the evolution of beneficial traits that made modern humans the most successful species in the world.
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