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How Cold War Nukes Helped Scientists Find the Longest-Lived Vertebrate

There might be Greenland sharks alive today that were born in Shakespeare's time.
A Greenland shark. Image: Julius Nielsen

The Greenland shark is one of the weirdest creatures in the ocean, and that's a competitive category. These animals live in cold, Arctic waters, and their flesh is toxic due to antifreeze-like compounds. Though they are among the largest predatory sharks, reaching lengths of 6.4 meters (21 feet), they grow and swim very slowly. Despite this lethargic pace, however, the remains of seals, reindeer, horses, and even polar bears have been found in their stomachs, so they clearly have no lack of appetite.


Now, new evidence published in Science shows that Greenland sharks are also the longest-lived vertebrate on record. Researchers led by University of Copenhagen marine biologist Julius Nielsen studied 28 female Greenland sharks caught as bycatch. The specimens ranged in size from 81 centimeters (2.7 feet) to over five meters (16.5 feet), from head to tail.

Based on the species' protracted growth rate of under one centimeter per year, Nielsen and his co-authors estimate that these deep sea Methuselahs may live three or four centuries—though admittedly, there is a large margin of error.

"We're not saying directly that we think the Greenland shark is 400 years old," Nielsen told me over Skype. "We're saying that with 95 percent certainty, it is between 272 and 512 years."

A Greenland shark caught as bycatch from research vessel Pâmiut in southwest Greenland. Image: Julius Nielsen

The authors cite a wide age range partially because very little is known about the Greenland shark, which spends much of its time in under-explored polar waters. They have been spotted at depths of over 7,000 feet, in dark, lonely regions where few submersibles dive, so opportunities to observe them in the wild are few and far between (as evidenced by this delightful video of a researcher reacting to a rare sighting).

"It would be really cool to get some more footage from the natural environment of Greenland sharks," Nielsen said.

Compounding the problem is the shark's lack of calcified tissue, which is normally one of the handiest indicators of age. To get around these limitations, Nielsen's team based their estimates on radiocarbon of the specimens' eye lenses, and used the "bomb pulse onset," generated by nuclear detonations during the mid-20th century, as a timestamp to approximate their ages.


"This is a different method than normally is applied to estimate the age of fish," Nielsen said.

"The numbers can definitely be improved, and I hope they will be improved in the future, because obviously 240 years of uncertainty is not super satisfying. But we decided that it was enough to, at least, go out and say that the longevity of this animal is measured in centuries."

Greenland shark in Disko Bay, western Greenland. Image: Julius Nielsen

Even if the Greenland shark was on the lower end of the age scale, at 272 years old, it would still be the longest-lived vertebrate known to science. The runner-up is the bowhead whale, which lives a measly 211 years.

Equally impressive is the advanced age at which female Greenland sharks reach sexual maturity. The new study estimates that females are ready to settle down and have their first litters around the ripe old age of 156, give or take 22 years. It's astonishing that these sharks are well into their centenarian years before they hit puberty. But since only one Greenland shark litter, consisting of ten pups, has ever been observed in utero, the finer details of the animal's reproductive behaviors are still largely unknown.

"We are very focused in some certain areas in the northern Atlantic where we have identified that these sexually mature females to occur quite often," Nielsen told me. "We have a lot of Greenland sharks out there, but most of them are sexually immature, and it would be really nice to know more about the ones that actually contribute to the population."

Understanding more about why and how Greenland sharks have evolved such longevity is fascinating on its own merits, but it could also have implications for extending human lifespans.

"Both [humans and Greenland sharks] are vertebrate animals," said Nielsen, "so they do of course have some things in common. It's definitely one of the perspectives of this study, besides knowing more about the Greenland shark, which is my personal interest in this project. It's possible that you can learn more about the processes of aging; both in vertebrates in general, and in the human body."

"Hopefully, in the future we will have more opportunities to investigate some of these things," he concluded. "There are many mysteries about the Greenland shark."