Sunday, 31 May 2015

The World's Oldest Stone Tools To Date

The earliest forms of stone tools are not much to look at: rounded rock hammers or flints with a rough edge for cutting or scraping. Looking at the ground, you could easily miss them among rocks shaped by natural forces. Oldowan tools were the first examples found in the Olduvai Gorge in Tanzania by palaeoanthropology's foremost family, the Leakeys. Dated to 2.6 to 1.7 million years old, the Oldowan tool industry coincided with an increase in brain volume of our early hominin ancestors. The use of tools allowed hominins to incorporate more protein, derived from prey, creating an increase in brain size originally triggered by the evolution of bipedalism.

The 3.3 million year old Lomekwi III site where the tools were identified
Yet new discoveries of older Oldowan tools are set to change the way we view our history as tool users and our evolutionary history.

Uncovered at the Lomekwi III site in Kenya, 149 stone tools were dated, using a mix of palaeomagnetics and radiometric dating, to 3.3 million years old. Those responsible for the tools have not been identified conclusively, but in 1999 the 3.3 million year old skull of the hominin Kenyanthropus platyops was found just a kilometre away from the site. Since then other fossils belonging to the species have been found closer to Lomekwi III.

Animal bones bearing cut marks were identified at Dikika in Ethiopia and dated to 3.39 million years old. Not only does this discovery push the history of stone tool usage further back in time, environmental studies of what the Lomekwi III site would have been like 3.3 million years ago have yielded some surprises. Analysis of carbon isotope ratios and animal fossils from the same horizon as the stone tools, conducted by Rhonda Quinn from Seton Hall University, showed that they all came from a forested environment.

One of the 3.3 million year old Lomekwi III tools
Previously, stone tool use was thought to have evolved in open savannah conditions where an increasingly dry climate and sparser resources forced new and innovative means of obtaining food.

Their origin in a forested environment suggests that the first stone tools may have served very different purposes, such as breaking open nuts and tubers or dead logs to access grubs and insects within. Equally intriguing is the method in which the tools were made.

The researchers tried knapping stones to recreate the Lomekwi tools and found that they could represent a technological stage between a hypothetical pounding-oriented stone tool use by an earlier hominin and the flaking-oriented knapping behaviour of later toolmakers. Chimpanzees and other primates are known to use stone to hammer open nuts, but using a stone for multiple purposes, and using one to crack apart another into a sharper tool, is more advanced behaviour.

'This is a momentous and well-researched discovery,' said palaeoanthropologist Bernard Wood from George Washington University, 'I have seen some of these artefacts in the flesh, and I am convinced they were fashioned deliberately.' The implications of these tools are extensive. Tool-making requires a high level of hand motor control; the age of the tools suggests that changes in the brain and spinal tract needed for such activity could have occurred before 3.3 million years ago. Clearly our evolution was on a fast track.