Ages are mounted on some archeological sites older than 50,000 years through argon-argon ( 40 Ar/ 39 Ar) dating of volcanic ash.

For dating, eggshells are better

But ash is not always current. In Africa, nonetheless — and before the Holocene, through the center East and Asia — ostrich eggshells are common. Some web sites also contain ostrich eggshell ornaments produced by early Homo sapiens.

Elizabeth Niespolo, during the time a graduate student in UC Berkeley’s Department of world and Planetary Science, splitting uranium from thorium in a lab at the Berkeley Geochronology Center. (Picture by Warren Sharp, BGC)

A graduate student in UC Berkeley’s Department of Earth and Planetary Science, conducted a thorough study of ostrich eggshells, including analysis of modern eggshells obtained from an ostrich farm in Solvang, California, and developed a systematic way to avoid the uncertainties of earlier analyses over the last four years, Sharp and Niespolo, at the time. (more…)