Scientists in Ethiopia have unearthed and dated some of the oldest stone hand axes, dating to 1.75 million years ago.
     The tools roughly coincide with the emergence of an ancient human ancestor called Homo erectus, and fossilised Homo erectus remains were found at the same site, said study author Yonas Beyene, an archaeologist at the Association for Research and Conservation of Culture in Ethiopia.
     "This discovery shows that the technology began with the appearance of Homo erectus," says Beyene. "We think it might be related to the change of species." However proving that was tricky, because the dating wasn't precise enough, said study co-author Paul Renne, a geochronologist and director of the Berkeley Geochronology Center in Berkeley, California.
     Human ancestors used primitive tools as far back as Homo habilis, 2.6 million years ago, but those - called Oldowan tools - weren't much more than rock flakes crudely knapped to a sharp edge. Nearly a million years later, more sophisticated two-sided hand axes emerged. These Aucheulean tools could be up to 20 centimetres long. Tools of this type have recently been discovered several hundred kilometres away near Lake Turkana in Kenya, dating to 1.76 million years ago.
     Beyene, Renne, and their colleagues have found more than 350 of these two-faced stone Aucheulean tools in Konso, Ethiopia, indistinguishable in age from those found in Kenya, and in different layers that span about a million years of human evolution - suggesting the symmetric hand axes were widespread in the region by that time. The techniques stayed similar until 800,000 years ago, when the edges on the tools became more refined.

Edited from LiveScience, NBC News (28 January 2013)