The earliest evidence of human ancestors using tools up to three million years ago has been unearthed in Kenya.

They were employing some of the oldest stone implements ever found to cut up hippo meat and pound plant material on the shores of Lake Victoria, say scientists.

The team explained that because fire would not be harnessed by hominins for another two million years, the toolmakers would have eaten everything raw, maybe pounding the meat into something like a "hippo tartare" to make it easier to chew.

The discovery is one of the oldest examples of the stone-age innovation known to scientists as the ‘Oldowan toolkit', as well as the oldest evidence of hominins eating very large animals.

Bones from at least three individual hippos were found at the site, according to the findings published in the journal Science, and two of the incomplete skeletons included bones that showed signs of butchery.

Archaeologists found a deep cut mark on one hippo's rib fragment and a series of four short, parallel cuts on the shin bone of another.

Antelope bones that showed evidence of hominins slicing away flesh with stone flakes or of having been crushed by hammerstones to extract marrow were also discovered.

Analysis of wear patterns on 30 of the stone tools found at the site showed that they had been used to cut, scrape and pound both animals and plants.

The international research team say various state of the art dating techniques suggest the artefacts are likely to be about 2.9 million years old, but they are certainly between 2.58 and three million years of age.

Study lead author Professor Thomas Plummer, of Queens College, City University of New York (CUNY), said: "This is one of the oldest if not the oldest example of Oldowan technology.

"This shows the toolkit was more widely distributed at an earlier date than people realized, and that it was used to process a wide variety of plant and animal tissues.

"We don't know for sure what the adaptive significance was, but the variety of uses suggests it was important to these hominins."

Excavations at the Nyayanga site also unearthed a pair of massive molars belonging to the human species' close evolutionary relative Paranthropus.

Study senior author Dr Rick Potts says the teeth are the oldest fossilized Paranthropus remains found, and their presence at a site laden with stone tools raises intriguing questions about which human ancestor made them.

Dr Potts, of the National Museum of Natural History in the US, said: "The assumption among researchers has long been that only the genus Homo, to which humans belong, was capable of making stone tools.

"But finding Paranthropus alongside these stone tools opens up a fascinating whodunnit."

The tools were found more than 800 miles from the previously oldest known examples of Oldowan stone tools.

Those 2.6-million-year-old implements were unearthed at Ledi-Geraru in Ethiopia could not be tied to any particular function or use.

Analysis of the wear patterns on the tools and animal bones discovered at Nyayanga suggests they were used by early human ancestors on various materials and food – including plants, meat and even bone marrow.

The researchers explained that the Oldowan toolkit includes three types of stone tools: hammer-stones, cores, and flakes.

Dr. Potts said: "With these tools you can crush better than an elephant's molar can and cut better than a lion's canine can.

"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."

The team were first attracted to the Homa Peninsula in Kenya by reports of fossilized baboon-like monkeys which are often found alongside evidence of human ancestors.

A series of digs at Nyayanga, beginning in 2015, unearthed 330 artifacts, 1,776 animal bones and the two hominin molars identified as belonging to Paranthropus.

Prof. Plummer said the artifacts were "clearly part" of the stone-age technological breakthrough that was the Oldowan toolkit.

He says that compared to the only other stone tools known to have preceded them – a set of 3.3-million-year-old implements unearthed at another site in Kenya – the Oldowan tools were a "significant upgrade" in sophistication.

Prof. Plummer explained that, over time, the Oldowan toolkit spread throughout Africa and as far as present-day Georgia and China, and it was not meaningfully replaced until around 1.7 million years ago.

Dr Potts added: "East Africa wasn't a stable cradle for our species' ancestors.

"It was more of a boiling cauldron of environmental change, with downpours and droughts and a diverse, ever-changing menu of foods.

"Oldowan stone tools could have cut and pounded through it all and helped early toolmakers adapt to new places and new opportunities, whether it's a dead hippo or a starchy root."

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