It has been a generally accepted hypothesis that in the long span of human evolution, the manufacture and use of stone tools was one of the characteristics distinguishing the ancestral Australopithecus genus from the more modern Homo. But a paper published in the journal Nature on August 11, 2010 may force a revision in scientists' understanding of early hominins and tool use. Archaeologist Shannon McPherron's fossil finds in Dikika, Ethiopia suggest that tool use was a far older skill than anyone previously realized.
Homo Habilis, the "Handy Man"
The making of stone tools serves as something of a benchmark in human evolution, a dividing line between more "primitive" ancestral species and the flowering of modern humans' own genus, Homo. Before this most recent find, archaeologists more or less agreed that hominin tool use began approximately 2.5 million years ago, and gave the hominin species alive at the time the name Homo habilis, or "handy man," to reflect this supposedly new leap in ingenuity. Fossil animal bones contemporary with Homo habilis show unmistakable signs of butchering with sharpened stones.
Did Australopithecus afarensis Also Use Tools?
The recent finds described in the Nature article, however, blur the boundary between Homo and the older australopithecines. In a layer of rock between two reliably dated volcanic layers, McPherron's team discovered the fossilized bones of two animals — one a cow-like ungulate and one a smaller goat-like mammal. When looked at under an electron microscope, these bones bore the distinctive, straight, parallel cut marks of stone tools. Additionally, chemical analysis of the bones showed that the cut marks had been made before fossilization had taken place, and that small chips of stone were embedded in the cuts.
The startling thing for the archaeologists was that the layer the fossils were found in was dated to 3.39 million years old, more than 800,000 years older than Homo habilis and into the range of Australopithecus afarensis, the species of the world-famous Lucy, who lived between three and four million years ago.
Tool Use and Human Brain Growth
If the smaller, more apelike australopithecines were actually manufacturing tools, then some hypotheses about the runaway brain growth that characterized the emergence of Homo will have to be revised or abandoned. It has long been speculated, for example, that tool use and the subsequent increase in meat eating was the main factor behind the great leap in intelligence that eventually led to modern humans. But if it can be definitively shown that both tool making and meat eating predated the leap, then other factors will have to be seriously considered.
At this stage, the archaeologists say, it is difficult to determine whether the fossilized animals found in Ethiopia were butchered by stone tools specifically made for the purpose, or by stones simply found and used as is. They point out, though, that even if australopithecines didn't actually make the tools, they might have held on to particularly effective ones they found and carried them around in tool kits, a behavior not seen in any other primate.
Sources:
McPherron, Shannon P. et al. "Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia". Nature. August 12, 2010
Pappas, Stephanie. "Discovery Pushes Human Tool Use Back 800,000 Years". LiveScience. August 11, 2010
Jenny Ashford - Jenny Ashford is a writer and graphic artist from central Florida. Her main area of interest in her Suite 101 articles is science, with a ...
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