Kevin Krajick. Scientists working in the desert badlands of northwestern Kenya have found stone tools dating back 3. The tools, whose makers may or may not have been some sort of human ancestor, push the known date of such tools back by , years; they also may challenge the notion that our own most direct ancestors were the first to bang two rocks together to create a new technology.
The discovery is the first evidence that an even earlier group of proto-humans may have had the thinking abilities needed to figure out how to make sharp-edged tools. Hominins are a group of species that includes modern humans, Homo sapiens , and our closest evolutionary ancestors. Anthropologists long thought that our relatives in the genus Homo β the line leading directly to Homo sapiens β were the first to craft such stone tools. But researchers have been uncovering tantalizing clues that some other, earlier species of hominin, distant cousins, if you will, might have figured it out.
The researchers do not know who made these oldest of tools. But earlier finds suggest a possible answer: The skull of a 3. The precise family tree of modern humans is contentious, and so far, no one knows exactly how K. Kenyanthropus predates the earliest known Homo species by a half a million years. This species could have made the tools; or, the toolmaker could have been some other species from the same era, such as Australopithecus afarensis , or an as-yet undiscovered early type of Homo.
To more sharply define the time period of the tools, Lepre and co-author and Lamont-Doherty colleague Dennis Kent examined magnetic minerals beneath, around and above the spots where the tools were found. By tracing the variations in the polarity of the samples, they dated the site to 3. This led to another surprise: The area was at that time a partially wooded, shrubby environment. Conventional thinking has been that sophisticated tool-making came in response to a change in climate that led to the spread of broad savannah grasslands, and the consequent evolution of large groups of animals that could serve as a source of food for human ancestors.
One line of thinking is that hominins started knapping β banging one rock against another to make sharp-edged stones β so they could cut meat off of animal carcasses, said paper co-author Jason Lewis of the Turkana Basin Institute and Rutgers.
