Stone axes estimated to be around 1.76 million years old have been discovered in Kenya, and are 350,000 years older than any other known complex tools, according to an article published online in Nature on Aug. 31.
These advanced tools were found in the same sediment layer as some cruder, more primitive chopping tools of a type known to be already in use for at least 1 million years.
The discovery was made on the banks of Lake Turkana by geologist Christopher Lepre at Columbia University, New York and his team.
The stone tools are up to 20 centimeters long and shaped on both sides. They would have been used to access meat and bone marrow from animal carcasses, such as antelopes and elephants.
Previously, the oldest known complex stone tools were from Ethiopia and estimated to be around 1.4 million years old, although some were found in India that could be 1 to 1.5 million years old.
The Kenyan stone axes seem to be Acheulian technology—distinctive oval-shaped stone tools found in various regions of Europe, Asia, and Africa.
But the more primitive tools found alongside are stone chunks with crudely chipped edges, and appear to belong to the Oldowan tool group—the earliest known stone tool industry in prehistory that existed before the emergence of Acheulian technology.
The scientists suggest that two different types of ancient humans with different tool-making abilities may have co-existed in the area at that time.
Acheulian tools are often associated with Homo erectus, a species widely believed to have come from Africa. Lepre and colleagues say the stone axes may have been made by H. erectus, while the Oldowan tools could have been made by H. habilis, a less capable early human.
Alternatively, it is possible these tools were used by only one type of ancient human.
“It might have been that a single species was capable of making both kinds of tools but that factors like what raw materials were available and what tasks needed to be conducted with the tools governed which types of tools were made,” said palaeoanthropologist Briana Pobiner at the Smithsonian Institution in Washington D.C., according to Nature.
