Earliest stone tool evidence revealed


August 11, 2010

Until  now the earliest evidence of stone tools was found at Gona in Ethiopia in 1994.  The artifacts have been securely dated to 2.6 million years and  were clearly manufactured, as opposed to shapes formed naturally by erosion or being tumbled in streams.  They corresponded in size, shape and apparent usage to the most rudimentary stone tool technology, called Oldowan and so named for stones found at Olduvai Gorge and dated to around two million years ago.  No hominin remains were found with these stones at Gona.

In a Nature article this week, a number of authors led by Shannon McPherron of the Max Planck Institute, announce the discovery of indirect evidence of stone tool use dating to 3.4 ma at Dikika, Ethiopia.  Dikika is a site across the river from Hadar, the fossiliferous area yielding, since 1973,a quantity of fossils attributed to Australopithecus afarensis, comprising the largest number of individuals attributed to any of our early human ancestors. The latest Dikika finds are two bones, the remains of two animals the size of modern goats and cows, showing cut and scrape marks.  These appeared to be deliberate, rather than the effects of natural abrasion, and were so confirmed by analysis under electron microscope.

Dikika is noted as the site where Zeresenay Alemseged, one of the authors of this week’s paper, found the “Dikika child”.  Discovered in November 2000, this find comprised the skull and post cranium remains of an infant who lived and died about 3.3 million years ago and determined to be Au. afarensis.. Dikika 55 is the site within the Dikika Rersearch Artera where these bones withj cut marks were found and attached is a photo of Dikika 55.

The cut mark bearing animal bones were found within the Sidi Hakoma formation, a securely dated geological al member found at Hadar and extending across the river to Dikika .As the authors state, “On the basis of low-power microscopic and environmental scanning electron microscope observations, these bones show unambiguous stone-tool cut marks for flesh removal and percussion marks for marrow access.”

David Braun, in a Nature comment, says “Paleoanthropologists have long associated tool use with the later part of human ancestors' evolutionary history. One of the key features of 'handy man' (Homo habilis), first discovered at Olduvai Gorge in Tanzania, was the use of stone tools. More recently, the discovery1 of sharp-edged stone tools in the Gona region of Ethiopia, dating to about 2.5 million years ago, modified this definition, extending the time over which tools were known to be used. But the implements found at these sites seemed too well made to have been early humans' first attempt at making such sharp-edged tools.

Evidence from the Dikika area of Ethiopia now indicates that human ancestors may have been practising for almost 800,000 years before the first appearance of chipped stone tools. [The authors] report that the fossilized bones of two animals show clear evidence of early humans using stones to remove scraps of flesh from the carcasses of large mammals. These bones were found in a region where the sediments are at least 3.2 million years old.“

The significance of this find lies not only in its antiquity but also its clear and unambiguous association with Au. afarensis.  Louis Leakey went to Africa in the 1930s seeking stone tools and the fossilized remains of our ancestors, believing only Homo and not some predecessor ape could have the capability of making and using tools. When fossils he named Homo habilis. or Handy Man, were found at Olduvai Gorge in 1966, he believed the proof had been found. The difficulty was that at this and other sites Both Homo and Australopithecus fossils have been found in association with older one industry tools and it has not been possible to make a clear and unambiguous association of the tools with one genus or the other. The Homo habilis remains at Olduvai were dated to about 2 million years ago.

The 2.6 million-year-old stone tools found at Gona had no hominin  fossils associated with them and slightly younger tools, at 2.3 million years, were found at had our, in possible association with early Homo. The discovery announced today, therefore, makes it clear that  the makers of the tools leaving the cut marks were members of the species Australopithecus afarensis as only  this species was extant in the Afar Depression during the period between four and 3 million years ago.

Attached are photographs of the cut marks.

Further details of the analytical process can be found at this link.

Link to additional comments in Nature .

On the day following the publication of their paper in Nature, two of the several authors addressed a "webmar" - web seminar - at Arizona State University.  They discussed their analysis of the marks found on the bones, their methodology for determining they could only have been made by stone selected by human hands for that purpose, and discussed other hypotheses as well.  Link to the webmar.



Cut marks on two bones