ARI SHAPIRO, HOST:
If you're looking for a way to stay young, you might want to try living out the rest of your life in the dark, frigid waters of the Arctic. You will also need to become a Greenland shark. Scientists have discovered this species can live for about 400 years and maybe even longer, as we hear in this encore report from NPR's Nell Greenfieldboyce.
NELL GREENFIELDBOYCE, BYLINE: The first time Julius Nielsen ever saw Greenland shark, he was working on a research vessel that was studying other Arctic fish.
JULIUS NIELSEN: One day we, by accident, caught a Greenland shark. It was a really a big one, and everyone went up and saw this interesting animal.
GREENFIELDBOYCE: It looked different than a great white shark, but it had the shark fins and big teeth. Nielsen was intrigued.
NIELSEN: You don't really expect sharks to be swimming around between icebergs and things like that.
GREENFIELDBOYCE: He soon learned that scientists know almost nothing about the Greenland shark.
NIELSEN: Perhaps, the biggest of the mysteries was how old these apparently very slow-growing sharks get.
GREENFIELDBOYCE: Biologists had some hints that these sharks grow less than a centimeter a year, but adult sharks can be over 16 feet long. So if they were really slow-growing, they'd have to live a long time.
To test that idea, Nielsen teamed up with some colleagues at the University of Copenhagen in Denmark where he works as well as researchers in other countries. They obtained 28 female Greenland sharks that were caught accidentally, and then they used radiocarbon dating techniques on the lenses of the sharks' eyes. The results were astonishing. These sharks live longer than any other creature advanced enough to have a backbone.
NIELSEN: We only expected that the sharks might be very old. And it was of course a very big surprise to learn that it was actually the oldest vertebrate animal in the world.
GREENFIELDBOYCE: The most likely age of the biggest, oldest shark was about 390 years. But there is some uncertainty in that estimate.
NIELSEN: What we can say is that it was with 95 percent certainty between 272 and 512 years old.
GREENFIELDBOYCE: The results appear in the journal Science, and they impressed Steven Austad. He studies the biology of aging at the University of Alabama at Birmingham.
STEVEN AUSTAD: It's a fascinating paper, and it certainly moves back to the vertebrate longevity record by a substantial amount.
GREENFIELDBOYCE: That record was held by the bowhead whale. Austad says its maximum lifespan has been shown to be at least 211 years. And while you hear other tales of long-lived turtles or fish, they're hard to verify.
AUSTAD: The reports are virtually all anecdotal.
GREENFIELDBOYCE: He says the Greenland shark age estimates are convincing. And if these sharks really can live as long as five centuries...
AUSTAD: That means the pilgrims, you know, may have been around the same time some shark that's swimming around now was born.
GREENFIELDBOYCE: Austad studies a kind of clam that can live for more than 500 years. Scientists know that because its shell has annual growth lines that can be counted like the rings inside a tree. He notes that the oldest specimens of this clam have come from waters near Iceland, and the bowhead whale and Greenland shark also both live far up north.
AUSTAD: So there does seem to be something that's attributable to cold or living in the cold that may confer longevity.
GREENFIELDBOYCE: He says it would be great to figure out what that icy secret is. Nell Greenfieldboyce, NPR News. Transcript provided by NPR, Copyright NPR.