Archaeologists in Kenya have dug up some of the oldest stone tools ever found,but who used them is a mystery.

In the past,scientists assumed that our direct ancestors were the only toolmakers.But two big fossil teeth found along with the tools at the Kenyan site belong to an extinct human cousin known as Paranthropus, according to a study published in the journal Science. This adds to the evidence that our direct relatives may not have been the only tool users and makers during the Stone Age.

The study found the tools date back about 2.9 million years, when early humans used them to hunt. The tools are likely to be the oldest examples of a very important Stone Age innovation known as the Oldowan toolkit. Dr Potts said these same kinds of tools had been found across Africa and beyond, showing they really caught on among early humans.

The site,known as Nyayanga,is a hilly landscape on the shores of Lake Victoria in Kenya. Slice marks on several hippo bones show that hippos were cut up for their meat, which would have been eaten raw.

The early humans were also likely to have used their tools to break open antelope bones for their fatty marrow (骨髓)inside, and to peel the outer rinds of tough plant roots, the study found. Stone tools allowed them to do that, even at this really early date,to extract(提取)a lot of resources from the environment.

The discovery of the teeth made it hard to rule out that other early humans were picking up tools of their own.After all,we can't say for sure whether the Paranthropus were using these tools,or just happened to die in the same place.

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Who used the oldest stone tools found in Kenya?

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