One of the lenses was pivotal. The third smallest of the 28 animals, it belonged to a shark that must have been born just around 50 years ago, just at the end of the bomb-testing era. That precise estimate allowed the team to ground-truth the others. Christopher Ramsey from the University of Oxford, an expert at carbon-dating, did this by creating a mathematical model that accounted for not just the 50-year-old’s age, but also how fast Greenland sharks grow, their size at birth, where they live, and other known factors.
The results? “We can say with 95 percent certainty that they’re between 272 and 512 years old,” says Nielsen. “But it’s most likely that it’s approximately 390.” With ages that big, there will always be uncertainty. But whichever of those numbers you pick, the Greenland shark is astonishingly long-lived. Among animals, it’s second only to the ocean quahog—an edible clam known to live to 507 years.
Chris Harvey-Clark from the University of British Columbia, who has probably clocked more time swimming with Greenland sharks than anyone else, says that the results are convincing, but will undoubtedly stir controversy. “Not a lot of people have published not a lot on radiocarbon dating for fishes,” he says. “The same thing happened with the bowhead whale: [the age estimates] were greeted with everything from hoots of delight to derision, but they stood the test of time.”
How do the sharks get so old? No one knows. “Part of the explanation, of course, is that it has a very big body—and a cold one,” says Nielsen. “They’re the same temperature as their surroundings and their preferred swimming temperature is -1 to 5 degrees Celsius. They have a slow metabolism. Maybe they have anti-ageing mechanisms, too, but I don’t know about that. I’m just a Greenland shark nerd.”
You can see why. There’s so much about them that we don’t know. “No one has ever seen a Greenland shark capture live prey,” says Nielsen. “And yet sometimes I’ve found entire seals inside their stomachs, and fast-swimming fish like Atlantic cod and halibut.” He thinks these remains were unlikely to have been scavenged, and yet it’s hard to imagine how an animal that’s supposedly so lethargic could taken down a speedy, agile seal. “I think they must be ambush predators that can sneak up on their prey. But no one knows.”
Meanwhile, a lot of “facts” about Greenland sharks are more like myths. The vast majority of them, including the one in the image above, have parasitic copepods (a type of crustacean) hanging off their eyes. That much is true, but according to Nielsen, the idea that the sharks are therefore blind is not. “When you look at hundreds of Greenland sharks, as I have done, you see that most of them have the parasite but they don’t have damage.”
The animals are not endangered. But Nielsen hopes that the results from his study will motivate people to find ways of reducing the numbers that are accidentally caught, and inspire scientists to learn more about the species. “We don’t know where they mate, where they give birth, how many there are,” he says. “When we go out, every time we go out, we learn something new.”
And in the meantime, if any studio would like to greenlight a centuries-spanning comedy drama about an aging Greenland shark that gets increasingly curmudgeonly and exasperated with each new human invention—the sequence with the first submarine alone would be golden—call me. Pixar?