An example of a human precision grip — grasping a first metacarpal from the thumb of a specimen of Australopithecus africanus that's thought to be 2 to 3 million years old.
T.L. Kivell & M. Skinner
An endangered Sumatran orangutan with a baby clings on tree branches in the forest of Bukit Lawang, part of the vast Leuser National Park, in Indonesia's Sumatra island.
Romeo Gacad/AFP/Getty Images