Mystery over 2.9 million years old prehistoric Kenyan stone tools

The Nyayanga site on the Homa Peninsula of Lake Victoria

The Nyayanga site on the Homa Peninsula of Lake Victoria in southwestern Kenya, where hundreds of stone tools dating to roughly 2.9 million years ago made by early human ancestors were found. PHOTO | J.S. OLIVER | HOMA PENINSULA PALEOANTHROPOLOGY PROJECT | HANDOUT VIA REUTERS

Scientists have a mystery on their hands after the discovery of 330 stone tools about 2.9 million years old at a site in Kenya, along Lake Victoria's shores, that were used to butcher animals, including hippos, and pound plant material for food.

Which of our prehistoric relatives that were walking the African landscape at the time made them? The chief suspect, researchers said on Thursday in describing the findings, may be a surprise.