Samples came from museums in Africa and elsewhere, and from Amina, an elephant that died naturally in Kenya in 2006, and from Misha, an African elephant euthanized in 2008 due to declining health at Utah's Hogle Zoo in Salt Lake City.
This African elephant has what are believed to be the biggest tusks among elephants at Kenya's Samburu National Reserve.
Illegal poaching of some 30,000 elephants a year for their ivory tusks threatens the animals with extinction.
Cerling and Uno conducted it with geologist Jay Quade, a former Utah doctoral student now at the University of Arizona; Daniel C.
Fisher, University of Michigan, Ann Arbor; George Wittemyer, Colorado State University; Iain Douglas-Hamilton, founder of Save the Elephants; and Samuel Andanje, Patrick Omondi and Moses Litoroh, all of the Kenya Wildlife Service.
Yet tons of illegal ivory still are sold because dealers claim the ivory was taken before the ban and there has been no test to prove them wrong – until now. "Currently 30,000 elephants a year are slaughtered for their tusks, so there is a desperate need to enforce the international trade ban and reduce demand." Only 423,000 African elephants are left.
"With an accurate age of the ivory, we can verify if the trade is legal or not" when the age is combined with existing DNA analysis to determine if an elephant is from Africa or Asia, says Uno, who earned his University of Utah Ph. Conservation groups say 70 percent of smuggled ivory goes to China.
How the Study Was Performed Neutrons from the nuclear tests bombarded nitrogen – the atmosphere's most common gas – to turn some of it into carbon-14.
Cosmic rays do that naturally at a low level, but open-air nuclear tests in the 1950s and 1960s sharply increased atmospheric, plant and animal carbon-14 levels, followed by a steady decline ever since.
The researchers tested the accuracy of carbon-14 dating in 29 animal and plant tissues killed and collected on known dates from 1905 to 2008.
The samples included elephant tusks and molars, hippo tusks and canine teeth, oryx horn, hair from monkeys and elephant tails, and some grasses collected in Kenya in 1962.
Ivory Trade Drives Elephant Slaughter International agreements banned most trade of raw ivory from Asian elephants after 1975 and African elephants after 1989.