Early human ancestors were using some of the oldest stone tools in the palaeontological record 2.9 million years ago to butcher hippos and pound plant material.
The findings come from a site on the shores of Lake Victoria in Kenya.
The horn of Africa is known as the “cradle of humanity” because it is so rich in early hominin fossils and artefacts, suggesting it as the birthplace of the primate lineage from which humans evolved.
Among the finds from this part of Africa are the oldest stone tools ever, dating back 3.3 million years, discovered in 2015 near Lake Turkana, also in Kenya.
Lake Turkana is also home of the 1.6-million-year-old fossil of a Homo ergaster dubbed “Turkana Boy,” the most complete early hominin skeleton ever found. Turkana Boy is a scientific marvel, representing one of the earliest hominins with features beginning to resemble those of modern humans.
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Though not the oldest stone tools ever discovered, the recent Lake Victoria finds are the oldest of a particular kind of stone tool belonging to what is called the “Oldowan toolkit.”
Oldowan tools are extremely significant in the development of early hominin production. They include simple flaked tools like choppers, scrapers and rudimentary cutting instruments.
The handaxes that were to replace Oldowan tools emerged hundreds of thousands of years later, around 1.7 million years ago.
There are three types of Oldowan tools: hammerstones, cores and flakes.
Hammerstones are used for hitting. Cores are typically angular or oval in shape. When a core is struck with a hammerstone, it creates flakes that can be used as a cutting or scraping edge.
“With these tools you can crush better than an elephant’s molar can and cut better than a lion’s canine,” says palaeoanthropologist Dr Rick Potts, head of the Smithsonian’s Human Origins Program. “Oldowan technology was like suddenly evolving a brand-new set of teeth outside your body, and it opened up a new variety of foods on the African savannah to our ancestors.”
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To date the tools, scientists used radioactive decay measurements of the sediment; reversal of Earth’s magnetic field; and other fossil finds in the same layer.
These multiple dating techniques place the tools from Lake Victoria at around 2.9 million years old, but more conservative estimates give a range of their construction between 2.58 million and 3 million years ago.
The site holds the fossil remains of at least three hippopotamus individuals – two of which bear the tell-tale signs that they were butchered. Similarly, antelope remains at the site show indications that the flesh was sliced off the bone, and that bones were crushed to get at the marrow inside.
“What’s really interesting is that here at this site you have some of the earliest evidence of butchery of megafauna, even before the advent of the use of fire,” says Associate Professor Julien Louys from Australia’s Griffith University. “This indicates that exploitation of megafauna began millions of years before the so-called megafauna extinction event.”
Fire hadn’t been invented for another two million years, so the meat may have been cut up to make it easier to chew.
Wear patterns on 30 of the stone tools discovered show they were also used to pound plants.
But which early hominins made the tools?
The site, and nearby sites, have produced molars belonging to close revolutionary relatives of humans, Paranthropus.
“The assumption among researchers has long been that only the genus Homo, to which humans belong, was capable of making stone tools,” Potts said. “But finding Paranthropus alongside these stone tools opens up a fascinating whodunnit.”