What was the scoop on living snails that seemed to be 27,000 years old?
Many biblical creationists, convinced that the world was but about 6,000 years old, or certainly not more than 10,000 years old, were posting on the internet examples of carbon dating test that produced obvious wrong results, even extraordinarily wrong results. One example was the story of how living snails were carbon dated and the results showed they were 27,000 years old. Atheist bloggers who make sport of challenging creationists were calling this utter nonsense. One prominent Atheist blogger wrote: “No person in their right mind would try to date--that is radiocarbon date--a living snail." Addressing himself to a particular creationist blogger he added: "Where do you get such ridiculous garbage.”
It wasn’t garbage. It turns out that a scientist had carbon dated living snails and didn't get those results. Alan Riggs with the U. S. Geological Survey did so. In 1984, he published a paper in The American Association for the Advancement of Science’s prestigious journal, Science, which reported that a live snail from an artesian spring in Nevada was found by carbon dating to be 27,000 years old. This, and numerous other such tests have taken on almost mythical proportions. What is often ignored are the explanations. Riggs had attributed the obvious error to the . . .
fixation of dissolved HCO3 [bicarbonate] with which the shells are in carbon isotope equilibrium. Recognition of the existence of such extreme deficiencies is necessary so that erroneous ages are not attributed to freshwater biogenic carbonates.
What this means in simpler terms is that the shells of the snails were formed from existing ancient material from which most of the carbon 14 had been depleted. It is an exception to the normal way carbon 14 is absorbed by living things. There is nothing wrong with carbon dating, per se. Riggs’ point was that what causes anomalies must be accounted for. To hold this example up as a reason to distrust carbon dating is completely bogus. But to suggest that there might be reasons, yet unknown, for being wary of tests on certain organic material was quite reasonable. Was linen such a material? What about Egyptian mummies? They are wrapped in linen.
Some shroud scholars who are not creationists by any means picked up this example as an anomaly that clearly showed that carbon dating wasn't always correct.