Tools discovered during wrong turn may push back human evolution trace by 500,000 years

By taking a wrong turn in a dry riverbed in Kenya, scientists discovered a trove of stone tools far older than any ever found before. Nobody knows who made them - or why.

At 3.3 million years, they push back the record of stone tools by about 700,000 years, and they are half-a-million years older than any known trace of the human evolutionary tree.