"Peking Man" is older than he looks. That's the conclusion of pioneering geochronologist Richard Teh-Lung Ku, whose new analysis of one of the most important finds in human evolutionary history indicates that the fossils date from at least 100,000 years earlier than scientists previously believed.
Ku dated the limestone caverns in which Peking Man dwelled at Zhoukoudian, not far from Beijing. In excavations that began in 1921, archeologists and paleontologists have recovered the remains of at least 40 individuals belonging to a hominid species that used fire and crudely fashioned stone tools but was anatomically distinct from Homo sapiens.
Working with professor Guanjun Shen of the University of Guizhou in China, Ku gathered cave limestone samples from the Peking Man site. Back in the lab, the researcher used state-of-the-art methods to show that the limestone from strata just above the layers containing Peking Man fossilized bones is close to 400,000 years old. Previous studies, using less advanced methods, dated the remains in the 200,000- to 300,000-year-old range.
Ku - a professor in the Department of Earth Sciences who was recently elected to fellowship in the American Geophysical Union for his pioneering work in the field of geochronology - helped develop the sophisticated methods used in the new analysis. The two scientists' preliminary findings will appear as a lead article in the August 1996 issue of the journal Acta Anthropologica Sinca, published in the People's Republic of China.
The dating of cave limestones ("speleothems") like those of Zhoukoudian uses principles of chemistry and nuclear physics. Such limestone forms where groundwater contains a high concentration of dissolved calcium and carbonate ions. When this water emerges from the ground, part of the dissolved carbonate "degasses" as carbon dioxide. At the same time, calcium carbonate precipitates, forming the spectacular deposits seen in limestone caves, such as stalactites, s
Contact: Eric Mankin
University of Southern California