1 September 2011

Oldest known advanced stone tools found

Newly discovered fossils in Northern Kenya have pushed back the development of ancient stone tool, complicating our understanding of early human history.
World's oldest Acheulian tool

World's oldest Acheulian tool yet known: A large crude hand axe from West Turkana in Kenya shaped by hard hammer percussion from a flat phonolite pebble.

Credit: P.-J. Texier, MPK/WTAP

west Turkana

Helene Roche (at left) leading archaeological excavations in the west Turkana area.
Credit: Rhonda L. Quinn

SYDNEY: Newly discovered fossils in Northern Kenya have pushed back the development of ancient stone tool, complicating our understanding of early human history.

Crude, pick-like tools found at the Kokiselei site in west Turkana have been dated to about 1.76 million years, which predates the previous earliest record of Acheulian artefacts by some 350,000 years.

Acheulian stone tools were shaped on both sides, said to be a step-up from earlier one-sided forms of the hand axe known as Oldowan tools. Both Oldowan and Acheulian stone tools were found to have co-existed at Kokiselei at this stage.

“We suspected that Kokiselei was a rather old site, but I was taken aback when I realised that the geological data indicated it was the oldest Acheulian site in the world,” said lead author Christopher Lepre, a geologist from Columbia University’s Lamont-Doherty Earth Observatory and Rutgers University, both in the U.S., of the paper published in Nature today. “We increased the antiquity of Acheulian culture by about 350,000 years.”

Co-existing at Kokiselei

Homo erectus – an early ancestor whose connection with humans today is under ongoing debate – most likely made hand axes of the Acheulian culture, said Lepre.

The Oldowan tools also present at the site likely originated from an earlier people, Homo habiliss, which suggests a branching evolutionary pattern in which ancestors and their descendants co-existed, he added.

The suggestion that Homo erectus made these tools 1.76 million years ago further complicates our understanding of human evolution because at around the same time, they also existed in Dmanisi in Georgia, presumably after the migration out of Africa, without these advanced bifacial tools. Excavations at the site in Dmanisi indicate that Homo erectus was only using Oldowan stone tool technology.

Lacking cultural presence

Co-author Dennis Kent, also from Rutgers and Lamont-Doherty, raised the obvious question: if Homo erectus had already developed the Acheulian hand axe, “why didn’t Homo erectus take these tools with them to Asia?”

Like a fad that takes time to spread, perhaps the Acheulian hand axe did not have the cultural presence 1.76 million years ago to be carried to Asia in the first migration out of Africa, said Lepre.

Another possibility is that the first early human to have migrated out of Africa was not Homo erectus, but was instead a species that utilised Oldowan tool-making methods, that then evolved once they had settled in Asia. It is even possible that the two groups migrated together after co-existing in Africa at Kokiselei, said Lepre.

Where we come from

Peter Hiscock, an archaeologist at Australian National University in Canberra who was not involved in the study, offered a cost-effectiveness analysis by considering both the ecological and economical value of stone artefacts. “The cost and benefit of making a tool depend on the context.” For the species migrating out of Africa, it may have been “more cost-effective to drop the technology while travelling”, meaning that Oldowan technology might have been more advantageous for the migrants.

“The research represents somewhat of a conundrum”, said Lepre. But what is clear from the findings is the fact that “we have to better understand the first migration out of Africa from a population and archaeological perspective.”

In other words, there is a difference between how various populations dispersed, and how the cultures that represented those populations dispersed. An understanding of where we come from and how that connects with other types of animals, specifically primates, gives humans a sense of where we are in the natural world, said Lepre. “It’s an interesting puzzle to go out to these ancient rock sites – really challenging, and a lot of fun.”


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