Perhaps delaying sex until you are 150 is the secret to longevity.
It seems to be working for the Greenland shark.
Scientists at the University of Copenhagen and Oxford have used a novel technique to determine that the giant carnivore that hunts in the north Atlantic is the world's longest living vertebrate.
Living up to 400 years means that the oldest of this species started hunting freezing waters when Pope Paul V was persecuting Galileo, Pocahontas arrived in England and Dutch explorer Dirk Hartog landed in Shark Bay, Western Australia.
The study, published on Friday in Science, also estimates sexual maturity at about 150 years.
"Wow!" said Mark McGrouther, ichthyology manager at the Australian Museum, when hearing about the study. "We've known that this species is long-lived, but that really is old."
Mr McGrouther, who was not connected with the study, said the museum had two specimens in storage but they were stuffed skins. He said they were the northernmost known shark species.
"This shark is related to the southern sleeper shark, that is in deep waters from the seamounts off Tasmania to the waters off Patagonia in Chile and Namibia and South Africa," he said.
Just how long these sharks live has been a mystery for decades.
Scientists normally look at seasonal growth layers in the calcified structures of sharks and rays, such as their fins, to determine age. However, given the particularly soft cartilage that forms the Greenland shark skeleton, this method isn't possible.
"We used established radiocarbon methods and combined then in a new way," said Julius Nielsen, lead author of the study and a doctoral student at the University of Copenhagen.
Danish and British scientists examined the eye lens nucleus of 28 female sharks. This part of the shark's eye is made up of inactive tissue, which is practically unchanged from when they are born.
Using radiocarbon dating, they compared the chemical composition of the shark eyes with shifts in the north Atlantic food chain to determine the age of the sharks.
They also examined the size of the sharks. Greenland sharks grow very slowly, less than 1 centimetre a year, said Mr McGrouther.
Of the 28 they studied, the average age was 2.72 metres. But the two largest sharks, at 4.93 metres and 5.02 metres in length, were estimated to be 335 and 392 years old, respectively.
Co-author of the study Professor Christopher Bronk Ramsey of Oxford University, said: "We had to take into account the complexity of the oceans and growth patterns of the shark when interpreting the data."
Mr McGrouther said: "Members of the Somniosus family, like the Greenland shark or southern sleeper shark, are very slow movers with very slow metabolisms. They only travel at about one kilometre an hour."
In the past, Greenland sharks have been found with entire polar bear and reindeer carcasses inside them. "That would be enough to feed them for a long time," Mr McGrouther said.
Given their speed and preference for icy waters, these huge carnivorous sharks are unlikely to be swallowing any humans.
