Stone Tools found in Ethiopia may indicate Humans are 80,000 Years Older Than Previously Thought

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Kate Ravilious, for National Geographic News, December 3, 2008

Modern humans may have evolved more than 80,000 years earlier than previously thought, according to a new study of sophisticated stone tools found in Ethiopia.

The tools were uncovered in the 1970s at the archaeological site of Gademotta, in the Ethiopian Rift Valley. But it was not until this year that new dating techniques revealed the tools to be far older than the oldest known Homo sapien bones, which are around 195,000 years old.

Using argon-argon dating—a technique that compares different isotopes of the element argon—researchers determined that the volcanic ash layers entombing the tools at Gademotta date back at least 276,000 years.

Many of the tools found are small blades, made using a technique that is thought to require complex cognitive abilities and nimble fingers, according to study co-author and Berkeley Geochronology Center director Paul Renne.

Some archaeologists believe that these tools and similar ones found elsewhere are associated with the emergence of the modern human species, Homo sapiens.

"It seems that we were technologically more advanced at an earlier time that we had previously thought," said study co-author Leah Morgan, from the University of California, Berkeley.

The findings are published in the December issue of the journal Geology.

Complicated family tree

The lack of bones at Gademotta makes it difficult to determine exactly who made these specialist tools and whether this really pushes the date of the beginning of modern humans, or Homo sapiens, back 80,000. Some archaeologists believe it had to be Homo sapiens while other experts think that our earlier ancestors may have had the required mental capability and manual dexterity.

Regardless of who made the tools, the dates help to fill a key gap in the archaeological record, according to some experts.

"The new dates from Gademotta help us to understand the timing of an important behavioral change in human evolution," said Christian Tryon, a professor of anthropology from New York University, who wasn't involved in the study.

If anything, the story has now become more complex, added Laura Basell, an archaeologist at the University of Oxford in the U.K.