Greenland sharks, which inhabit the cold and dark waters of the Arctic, might look dim-witted with their blunt snouts and gaping mouths. But these sharks are the longest-living vertebrates on Earth; some of them could even be as old as 600 years
Into the deep
Once widely hunted for their liver oil, today these sharks are just considered as by-catch, writes M R O’Connor in The New Yorker. Scientists determine the age of other sharks by reading the rings formed in their calcified vertebrae. But Greenland sharks have no hard tissues, even their vertebrae are soft. Scientists had to devise a new method to determine the age
Nuke tests and carbon dating
To determine the age, Danish marine biologist Julius Nielsen and his team harvested eyes from 28 Greenland sharks. The scientists then measured the amount of the radioactive isotope carbon-14 in the lenses. This method was based on the paper published nine years ago by a physicist Jan Heinemeier and four of his colleagues
Heinemeier’s paper was on lens crystallines, a class of proteins found in the human eye. These crystallines contain carbon and carbon-14. Crystallines, unlike other proteins which undergo constant recycling, remains stable throughout a person’s life. The isotope has always occurred naturally on Earth but some of the current supply comes from nuclear tests. The level of C-14 changes from year to year and there was a huge spike during the fifties and sixties—when N-tests were rampant