Nuclear bomb tests 50 years ago have given us a conservation weapon. Determining the levels of radioactive isotope in ivory should allow us to find out whether it is being illegally traded.
The amount of carbon-14 in the atmosphere peaked in 1962 just before the introduction of an international ban on surface testing of nuclear weapons. The rapid rise and subsequent decline of this isotope is known as the bomb curve.
Animal cells take up carbon-14 when they are formed, and because the decay rate of carbon-14 is known, the time of death can be deduced from the amount of isotope left. Linking the amount of carbon-14 found in organic material with the bomb curve has been used to date human tooth enamel and even regenerating brain cells.
Kevin Uno at Columbia University in Palisades, New York, and colleagues have now used the technique to test 29 samples including elephant tusks and rhino horn collected in East Africa. They dated them to within about 1.4 years of the known collection date.
The technique could be used to age confiscated animal parts – to determine, say, whether African elephant ivory was harvested before or after the 1989 trade ban. Or it could be used as part of a series of forensic techniques to separate ivory obtained during legal culls – necessary to control some elephant large populations – from illegal poaching, says Elias Sideras-Haddad of the University of the Witwatersrand in Johannesburg, South Africa, who proposed a similar dating technique in 2001.
But Sideras-Haddad points out that the window for carbon-14 dating is closing, because atmospheric levels will soon have returned to pre-1950s amounts. "You can see from the bomb curve we are nearly back to normal levels," he says.
Journal reference: PNAS, DOI: 10.1073/pnas.1302226110
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
Have your say
Only subscribers may leave comments on this article. Please log in.
Only personal subscribers may leave comments on this article
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
