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Cutting-edge technology. A stone core (lower left) and three of the recently found blades.

Cara Roure Johnson and Sally McBrearty/University of Connecticut

Oldest Stone Blades Uncovered

CHICAGO, ILLINOIS--Paleoanthropologists working in Africa have discovered stone blades more than a half-million years old. That pushes the date of the earliest known blades back a remarkable 150,000 years and raises a question: What human ancestor made them?



Johnson and McBrearty found the stone blades in a basalt outcrop known as the Kapthurin Formation, including four cores from which the blades were struck. "These assemblages would have been made by a different species of human," Johnson said. "Who were they?" The blades come from the same part of the formation where researchers have found two lower jaws that have been variously described as belonging to Homo heidelbergensis or H. rhodesiensis, human ancestors in Europe and Africa that predate the origin of our species, H. sapiens.

Regardless of the identity of the toolmakers, other researchers say that the discovery of blades this early suggests that these toolmakers were capable of more sophisticated behavior than previously thought, perhaps as a result of the last dramatic expansion of brain size in the human lineage about 600,000 years ago. "It's reflective of a major shift in human cognition," says Alison Brooks, a paleoanthropologist at George Washington University in Washington, D.C.

To convince most researchers that such a dramatic breakthrough really took place so early in human evolution, however, anthropologists will have to find more blades this ancient, says paleoanthropologist Rick Potts of the Smithsonian Institution in Washington, D.C. Stay tuned: The search is already under way for more African blade runners.