August 18, 2010Posted by on
The oldest known human tool technology is known as Oldowan. These tools were originally thought to have been the handiwork of an early member of our genus, Homo. In fact, Louis Leakey and colleagues named the species Homo habilis (literally “handy man”) because of its association with Oldowan stone tools. There is an almost doubling in brain volume and expansion of the frontal lobes in habilines compared to their australopithecine antecedents, which some have attributed to the formers use of stone tools.
Stone tools found during excavations in the early 1990s in the Afar region of Ethiopia have been dated to between 2.5 and 2.6 million years. However, H. habilis does not first appear on the scene until around 2.3 million years ago, which would make australopithecines or paranthropines the most likely authors of this assemblage. Even these earliest stone tools have been deemed too advanced for our first foray into stone tool making and many researchers predicted that even earlier tools were awaiting discovery.
Researchers working in the Dikika region of Ethiopia have recently uncovered bones dating to between 3.2 and 3.4 million years ago that show all the hallmarks of butchering. The cut marks and percussion marks are suggestive of defleshing and the removal of bone marrow. From a behavioural aspect, it is unclear whether this represents hunting or the scavenging of recently dead animals.
Bone trauma can be an incredible tricky thing to interpret. Trampling, tooth marks from scavenging, direct contact with rocks, among other agents can leave pseudo-cut marks on a bone. The bones were analysed under scanning electron microscope, with the researchers concluding that stone tools were most likely responsible for the cut marks and fracture patterns.
Australopithecus afarensis is the only known hominin to date from this time period and is, for the time being, the best candidate for making these marks. Tool use is seen in both our ape and monkey cousins and it seems likely that A. afarensis also utilised tools. Researchers have shown that A. afarensis would have been capable of the manual dexterity needed to manipulate tools. What is less clear is whether these cut marks were made by stone tools specifically fashioned for butchering or whether these hominins used sharp-edged natural stones. Whether these were fabricated or natural they were still used as tools. However, the dentition of A. afarensis suggests that meat constituted a negligible part of their diet. The large molars and thick enamel of this hominin point to a diet rich in tubers and other vegetation.
The elephant in the room is the absence of any tools at the Dikka site. This is unusual since tools, which ordinarily preserve better, typically outnumber bones at butchering sites. It is also unclear how many bones were collected at the site and why none of these show tool marks. Indeed, the entire evidence consists of only two small fragments of fossilised bone. The authors suggest that the lack of additional bones with cut marks could indicate that the bones were processed off-site, where better quality tools were available.
The evidence is tantalising but more is needed. Hopefully, further excavations at Dikka will uncover the missing stone tools and the humans who made them.
Alba DM, Moyà-Solà S, Köhler M. 2003. Morphological affinities of the Australopithecus afarensis hand on the basis of manual proportions and relative thumb length. Journal of Human Evolution 44: 225–254.
McPherron SP, Alemseged Z, Marean CW, Wynn JG, Reed D, Geraads D, Bobe R, Bearat HA. 2010. Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikka, Ethiopia. Nature 466:857-860.