ANN ARBOR – A team of international researchers led by the Cleveland Museum of Natural History has made an incredible discovery.
Led by Yohannes Haile-Selassie, a curator at the museum, the team, including U-M geologist Naomi Levin, discovered a "remarkably complete" cranium of an early human ancestor that is 3.8 million years old at the Woranso-Mille paleontological site in Ethiopia's Afar region, located 550 km northeast of the capital city, Addis Ababa.
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The team has been operating at the site since 2004 and has collected more than 12,600 fossil specimens from 85 mammalian species. The cranium, however, is its oldest fossil discovery.
The findings were published in two papers in the international scientific journal Nature on Wednesday.
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The cranium (MRD-VP-1/1), referred to by researchers as "MRD," was discovered in February 2016. Since its discovery, project geologists have been working to determine the specimen's age and context by dating minerals in the layers of nearby volcanic rocks while paleoanthropologists have conducted thorough analyses of the cranium.
The discovery of early human ancestor fossils is extremely rare, and MRD represents a time span 4.1 to 3.6 million years ago.
Researchers believe that the fossil is likely an Australopithecus anamensis, an ancestor of Lucy's species, Australopithecus afarensis. Analyses of MRD also demonstrated that both species coexisted for roughly 100,000 years, challenging prior assumptions that these two early human ancestors experienced a linear transition. The specimen was found just 55 km north of Hadar, also known as "Lucy's Site."
"This is a game changer in our understanding of human evolution during the Pliocene," Haile-Selassie said in a statement.
Local Afar worker Ali Bereino discovered the first piece of the specimen -- the upper jaw -- on Feb. 10, 2016. The remainder of the specimen was discovered in the area shortly after.
"I couldn't believe my eyes when I spotted the rest of the cranium," Haile-Selassie said in a statement. "It was a eureka moment and a dream come true."
U-M's Levin led an interdisciplinary team from various institutions in environmental reconstruction work at the site.
"MRD lived near a large lake in a region that was dry," Levin, an associate professor in the U-M Department of Earth and Environmental Sciences said in a statement. "We're eager to conduct more work in these deposits to understand the environment of the MRD specimen, the relationship to climate change and how it affected human evolution, if at all."
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