Arizona State University researchers unearthed fossils in Ethiopia that may have belonged to a previously undiscovered species of human ancestor.
The researchers say they found 2.6 million-year-old fossilized teeth from an offshoot of an extinct group of primates called Australopithecus. And they say it’s possible the teeth belong to a new species, because of their shape and when they appear in the fossil record.
“Lucy, her species' last evidence for her, is around 3 million years or so,” said Christopher Campisano, ASU geologist and study co-author. “And then we pick up this new material around, say, 2.7 million years.”
Lucy is notable for being the most-complete fossilized skeleton ever found that derived from the species Australopithecus afarensis.
The specimens found in this most recent paper were collected between 2015 and 2018 as a part of the Ledi-Geraru research project.
ASU researchers say the latest fossils were also found to exist around the same time as some of the first homo species, dating from 2.78 and 2.59 million years ago. Homo is the genus of primates that humans — homo sapiens — belong to.
The team says it’s too soon to confirm if these Australopithecus teeth actually belong to a new species, but there are some indicators.
“When you compare it to a suite of other known material from known taxa, it sort of falls, you know, either outside of the range of variation or on the edges of range of variation of what we know,” Campisano said. “And so, in the paper, we put up a couple different hypotheses that — or probabilities that — this could represent.”
The team was able to date the fossils by examining volcanic-ash minerals called feldspar, which would have crystallized at the time of the eruption.
“They contain potassium that radioactively decays to argon, and we can use that decay method … to then date those feldspars,” Campisano said. “So what we're essentially dating is multiple units of volcanic ashes in these sequences, and the fossils are in a bed with those volcanic-ash sequences.”
The research team includes a mix of experts from different fields, including paleontologists and geologists like Campisano.
“We have people specific to the dating, whether it's argon dating or paleomagnetic dating, and so it is a huge, multidisciplinary project,” he said. “Again, this is very common in paleontology and archaeology and other disciplines, as well. And so we all sort of have our little role to do, basically, and we all work together.”
For Campisano, studying the lineage of human evolution is about more than scientific discovery.
“These sorts of projects sort of put you in touch with your humanity and show us that we all sort of have this common ancestry,” Campisano said. “Whatever is happening in the world, you know, you can go out on these landscapes and hike around and find the origins of all of this.”
The study was published in the journal Nature.
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