2.4-Million-Year-Old Stone Tools Found In Algeria Could Rewrite Human Origin Story
2.4-Million-Year-Old Stone Tools Found In Algeria Could Rewrite Human Origin Story
Early human ancestors hunted extinct horses, antelopes, and other creatures with primitive stone tools from 2 million to 2.4 million years ago on a high grassy plateau in Algeria, just 100 kilometers from the Mediterranean Sea.
The dates, published today, push back by as much as half a million years the age of North Africa’s oldest tools and provide new insight into how these protohumans spread across the continent.
East Africa has been known as the birthplace of our genus Homo for decades, and the epicentre of early toolmaking for nearly 1 million years.
The oldest known Homo fossils date back 2.8 million years in Ethiopia. Nearby, just 200,000 years later, scientists have found simple tools, such as thumb-size stone flakes, and fist-size cores from which such flakes were struck, in the nearby Rift Valley of Ethiopia.
Claims of even older tools and animal bones with cutmarks stretch back 3.4 million years in east Africa, but those claims are controversial.
Regardless, the long-standing view has been that once hominins, or members of the human family, invented stone tools in east Africa, they didn’t travel far with them until 1.8 million years ago (or, more controversially, 2 million years ago, in China) when tools turn up in Algeria, Georgia, and China.
The new study upends this view. After 25 years of excavations at the Ain Hanech complex—a dry ravine in Algeria—an international team reports the discovery of about 250 primitive tools and 296 bones of animals from a site called Ain Boucherit.
About two dozen animal bones have cut marks that show they were skinned, defleshed, or pounded for marrow.
Made of limestone and flint, the sharp-edged flakes and round cores—some the size of tennis balls—resemble those found in east Africa.
Both represent the earliest known toolkit, the so-called Oldowan technology, named for the site where they were found 80 years ago at Olduvai in Tanzania.
Ain Hanech lacks volcanic minerals, which provide the gold standard for dating sites in eastern Africa. Instead, the researchers used three other dating methods, notably paleomagnetic dating, which detects known reversals in Earth’s magnetic field that are recorded in rock.
The tools and cut-marked bones date as far back as 2.4 million years ago, the researchers report today in Science. They also used the identity of large, extinct animals, such as mastodons and ancient horses, to confirm the dates.
The cut-marked bones represent “the oldest substantive evidence for butchery” anywhere, says paleoanthropologist Thomas Plummer of the City University of New York’s Queens College, who was not involved with the study.
Although other sites of this age in east Africa have stone tools, the evidence for actual butchery of animals is not as strong, he says.
At Ain Hanech, the dates provide “convincing evidence for stone tools and cut-marked bones at about 2 million years or more,” says geochronologist Warren Sharp of the Berkeley Geochronology Center in California. But he finds the 2.4 million date “less compelling,” because of potential issues with the dating methods.
Whether the tools are 2 million or 2.4 million years old, they suggest toolmakers had spread farther and wider across Africa earlier than previously known.
“There must have been a corridor through the Sahara with movement between east Africa and North Africa,” says paleoanthropologist Rick Potts of the Smithsonian Institution’s National Museum of Natural History in Washington, D.C.
Alternatively, the new dates suggest hominins in at least two different parts of Africa, separated by 5000 kilometers, were sophisticated enough to independently invent rudimentary stone tools and habitually make them, Potts says.
Either way, the study suggests that by 2 million years ago or so, making stone tools and butchering meat with them was routine for human ancestors in distant corners of the African continent. And this technological revolution may have given them the tools they needed to travel farther and wider across Africa and beyond.