In an accidental discovery that will upturn many existing theories, scientists have found stone tools dating back 3.3 million years in northwestern Kenya, the oldest such artifacts yet discovered. This age is long before the advent of modern humans. The tools, whose makers may or may not have been some sort of human ancestor, push the known date of such tools back by 700,000 years. The discovery is described in a new paper published in the leading scientific journal Nature.
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. The stone tools mark “a new beginning to the known archaeological record,” say the authors of a new paper.
“The whole site’s surprising, it just rewrites the book on a lot of things that we thought were true,” said geologist Chris Lepre of the Lamont-Doherty Earth Observatory and Rutgers University, a co-author of the paper who precisely dated the artifacts.
The new find came about almost by accident: Harmand and Lewis said that on the morning of July 9, 2011, they had wandered off on the wrong path, and climbed a hill to scout a fresh route back to their intended track. They wrote that they “could feel that something was special about this particular place.” They fanned out and surveyed a nearby patch of craggy outcrops. “By teatime,” they wrote, “local Turkana tribesman Sammy Lokorodi had helped [us] spot what [we] had come searching for.”
By the end of the 2012 field season, excavations at the site, named Lomekwi 3, had uncovered 149 stone artifacts tied to tool-making, from stone cores and flakes to rocks used for hammering and others possibly used as anvils to strike on.
The tools “shed light on an unexpected and previously unknown period of hominin behavior and can tell us a lot about cognitive development in our ancestors that we can’t understand from fossils alone,” said lead author Sonia Harmand, of the Turkana Basin Institute at Stony Brook University and the Universite? Paris Ouest Nanterre.
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 – the line leading directly to Homo sapiens – were the first to craft such stone tools. But researchers have been uncovering tantalizing clues that some other, earlier species of hominin, 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 3.3-million-year-old hominin, Kenyanthropus platytops, was found in 1999 about a kilometer from the tool site. A K. platyops tooth and a bone from a skull were discovered a few hundred meters away, and an as-yet unidentified tooth has been found about 100 meters away.
The precise family tree of modern humans is contentious, and so far, no one knows exactly how K. platyops relates to other hominin species. 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.
Lepre said a layer of volcanic ash below the tool site set a “floor” on the site’s age: It matched ash elsewhere that had been dated to about 3.3 million years ago, based on the ratio of argon isotopes in the material. 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.
Lepre’s wife and another co-author, Rhoda Quinn of Rutgers, studied carbon isotopes in the soil, which along with animal fossils at the site allowed researchers to reconstruct the area’s vegetation. 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 – banging one rock against another to make sharp-edged stones – so they could cut meat off of animal carcasses, said paper co-author Jason Lewis of the Turkana Basin Institute and Rutgers. But the size and markings of the newly discovered tools “suggest they were doing something different as well, especially if they were in a more wooded environment with access to various plant resources,” Lewis said. The researchers think the tools could have been used for breaking open nuts or tubers, bashing open dead logs to get at insects inside, or maybe something not yet thought of.
Earlier dating work by Lepre and Kent helped lead to another landmark paper in 2011: a study that suggested Homo erectus, another precursor to modern humans, was using more advanced tool-making methods 1.8 million years ago, at least 300,000 years earlier than previously thought.
“I realized when you [figure out] these things, you don’t solve anything, you just open up new questions,” said Lepre. “I get excited, then realize there’s a lot more work to do.”
SOURCE: INDIA TIMES
