U-Pb isotopic age of the StW 573 hominid from Sterkfontein, South Africa

Sterkfontein cave, South Africa, has yielded an australopith skeleton, StW 573, whose completeness has excited great interest in paleoanthropology. StW 573, or "Little Foot," was found 25 meters below the surface in the Silberberg Grotto. 238U-206Pb measurements on speleothems immediately above and below the fossil remains, corrected for initial 234U disequilibrium, yield ages of 2.17 +/- 0.17 million years ago (Ma) and 2.24(-0.07)(+0.09) Ma, respectively, indicating an age for StW 573 of close to 2.2 Ma. This age is in contrast to an age of approximately 3.3 Ma suggested by magnetochronology and ages of approximately 4 Ma based on 10Be and 26Al, but it is compatible with a faunal age range of 4 to 2 Ma.