Washington, Dec 4 : A new study of sophisticated stone tools found in Ethiopia has led scientists to suggest that modern humans may have evolved more than 80,000 years earlier than previously thought.
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.
According to a report in National Geographic News, 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 sapien.
"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.
Gademotta was an attractive place for people to settle, due to its close proximity to fresh water in Lake Ziway and access to a source of hard, black volcanic glass, known as obsidian.
"Due to its lack of crystalline structure, obsidian glass is one of the best raw materials to use for making tools," Morgan explained.
In many parts of the world, archaeologists see a leap around 300,000 years ago in Stone Age technology from the large and crude hand-axes and picks of the so-called Acheulean period to the more delicate and diverse points and blades of the Middle Stone Age.
At other sites in Ethiopia, such as Herto in the Afar region northeast of Gademotta, the transition does not occur until much later, around 160,000 years ago, according to argon dating.
This variety in dates supports the idea of a gradual transition in technology.
"The new date for Gademotta changes how we think about human evolution, because it shows how much more complicated the situation is than we previously thought," said Laura Basell, an archaeologist at the University of Oxford in the U.K. It is not possible to simply associate specific species with particular technologies and plot them in a line from archaic to modern," she added.