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No. 100: Jul-Aug 1995

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Microbes Threaten Radiocarbon Dating

In the 1980s, skeptics had a lot of fun debunking the Shroud of Turin, the supposed burial cloth wrapped around Christ. Their glee was unbounded when radiocarbon dating "proved" that the shroud could not be older than 700 years. The skeptics may have been too quick to celebrate, because the samples that were sent to the radiocarbon lab may not have been wholly cloth.

The reality of our biosphere is that virtually everything is permeated with microbes and their products. S.J. Mattingly and L.A. Garza-Valdes, of the University of Texas at San Antonio, have been studying "biogenic varnishes" for years. These plastic-like coatings are produced by bacteria and fungi. Sure enough, microscopic examination of a few linen fibers from the Shroud of Turin show that they, too, are coated with such varnishes. These biogenic varnishes may introduce carbon that has been recently fixed from the atmosphere and thus make the sample's age appear younger than it really is.

(Travis, John; "Microbes Muddle Shroud of Turin's Age," Science News, 147:346, 1995.)

Comment. More than the Shroud is at stake here. Bacteria contaminate just about everything, including wood and bone from archeological sites. Bacteria may, therefore, "rejuvenate" samples sent in for radiocarbon dating. The importance of this phenomenon is still unclear.

Cross reference. Radiocarbon-dated samples may also appear erroneously "aged" by the uptake of primordial carbon (C13) present in the earth's crust. See SF#99.

From Science Frontiers #100, JUL-AUG 1995. 1995-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987