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Science 26 June 1998:
Vol. 280. no. 5372, pp. 2041 - 2042
DOI: 10.1126/science.280.5372.2041
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News & Comment

CARBON DATING:
Rock Dates Thrown Into Doubt, Researcher Under Fire

David Malakoff

The age of some striking Arizona petroglyphs is being called into question in a Technical Comment in this issue (p. 2132) challenging the validity of the technique used. The method uses accelerator mass spectrometry radiocarbon analysis to date microscopic quantities of carbon-rich organic material that are believed to become trapped beneath a thin layer of natural varnish on rocks. The researcher who pioneered the method acknowledges that his technique is flawed and produces "ambiguous" results but counters that faulty lab technique explains why other researchers have been unable to replicate his results. The controversy has sparked inquiries by the National Science Foundation and the university where the research was performed and is likely to cast a cloud over rock-varnish science as a whole.

David Malakoff is a writer in Bar Harbor, Maine.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)