Christopher JoyceChristopher Joyce is a correspondent on the science desk at NPR. His stories can be heard on all of NPR's news programs, including NPR's Morning Edition, All Things Considered, and Weekend Edition.
A flint-knapper makes sharp stone flakes by striking a flint "core" with a hammerstone.
Human Origins Initiative
Feet On The Ground: Barefoot runners tend to land on the balls of their feet rather than on their heels the way most shoe-runners do. Rick Roeber went shoeless in 2003 and has clocked more than 13,000 barefoot miles since.
An offshore oil rig is seen in the Catalina Channel near Long Beach, Calif., in 2008. On Monday, Gov. Arnold Schwarzenegger withdrew his support for a controversial new offshore oil drilling project off the Santa Barbara coast.
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