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Human Ancestors Discovered In Ethiopia Show Complex Behaviors, Tool Use

The 1.5 million-year-old fossils of human ancestors recently unearthed in Ethiopia show sophistication in behaviors and tool use, said the Case Western Reserve University (CWRU) researchers who found them, despite one example having the smallest cranium of any specimen found in Africa to date.

One Homo erectus female cranium found is a little less than half the size of our brains, said CWRU anatomy professor Scott Simpson, who worked with the team that discovered the fossils.

Alongside the fossils were two types of tools: Oldowan, which consisted of broken off pieces of stone used as a tool, and Acheulian, which was a more precise tool made with a complex process of flaking bits off a piece of stone. Concurrent use of both tools shows sophistication, Simpson said.

“Humans make the false assumption that our ancestors are stupid,” Simpson said. “Every time we go back and find direct evidence of their biology or their behavior, we find that our human ancestors were much more adept at living in their environment and taking advantage of all the resources that were available for them.”

The brain of the female fossil would be around 590 milliliters, Simpson said, which puts it at less than half the size of modern human brains. That’s also about 100 to 150 milliliters smaller than the next-larger H. erectus, he said.

“With a brain that size, they were still able to make very sophisticated tools, like Acheulian and Oldowan stone tools,” Simpson said. “It shows that they were doing quite a lot with a little bit of gray matter.”

The two samples were found roughly 3.5 miles (5.7 kilometers) apart in Gona, Ethiopia, according to a CWRU press release. The Gona study area is adjacent to the Middle Awash and Hadar study areas where human ancestors Lucy and Ardi were found previously and not far from the Woranso-Mille site, where CWRU paleoanthropologist Yohannes Haile-Selassie recently discovered a 3.8 million cranium fossil.

The fossils provide insight into the amount of anatomical variation in the species, Simpson said. And there are anatomical characteristics that connect the human ancestors found in Ethiopia with fossils found elsewhere, Simpson said, even as far away as China.

“One of the questions that we have about Homo erectus is, was Homo erectus a species that lived in Africa and Eurasia, or are we lumping a bunch of different species together?” Simpson said.

Theteam in Ethiopia is also examining animal remains and other fossils in the area to learn more about the environment and context of human ancestors’ lives, he said.

“Each fossil that we find and each artifact that we find contributes to the puzzle,” Simpson said. “We still have a lot of pieces that are missing, but every new piece provides an insight into what we looked like and what we did millions of years ago.”

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