According to a story in Canada.com researchers out of the University of Toronto, working at the Kuruman Hills in South Africa, have discovered stone tools use in layers dated to around 2 million years ago:
"Geological evidence indicates that these tools were deposited in the cave by human ancestors, not washed into the site from the outside," said a University of Toronto statement on Friday announcing the discovery. "The combination of stone tools indicating the presence of human ancestors, and the dating of the lead levels, to the conclusion that human ancestors were in the cave two million years ago. This is the earliest evidence for intentional cave occupation by human ancestors."
Smarter than we thought.