A shark swimming under the Arctic ice today may have been alive before the Mayflower sailed

In the cold, dark water beneath the Arctic ice swims an animal that may be older than the United States, older than most of the books in any library, and old enough to have shared the ocean with sailors from the age of exploration. The Greenland shark grows so slowly and lives so long that a single individual can span multiple centuries, making it the longest-lived vertebrate known to science.

For most of history no one could say how old these sharks actually were, because they lack the hard, layered structures that researchers normally use to age fish. The answer, when it finally arrived, came from an unlikely place: the chemistry locked inside the animal’s eyes. The numbers that emerged were so extreme that they reset expectations for how long a backboned animal can live.

Dating a shark by the chemistry of its eyes

The breakthrough hinged on a peculiar feature of the eye. The center of a shark’s eye lens forms before birth and then stays chemically inert for the rest of the animal’s life, sealing in the carbon that was present when the tissue first developed. By measuring radioactive carbon in those lens nuclei, scientists could estimate when each shark was born. The study that pioneered the approach, published in the journal Science, applied radiocarbon dating to the eye lenses of Greenland sharks to reconstruct ages that no other method could reach. A useful check came from twentieth-century nuclear weapons testing, which left a detectable spike of carbon-14 in the environment in the early 1960s; only the smallest, youngest sharks in the sample carried that marker, confirming that the larger animals had been born well before it.

That combination of techniques gave the ages a firm anchor. The older sharks predated the atomic era entirely, and the youngest could be pinned to the decades after the bomb pulse appeared.

A lifespan measured in centuries

The results were staggering. Analysis of 28 female Greenland sharks indicated a lifespan of at least 272 years, and the largest specimen was estimated at around 392 years old, establishing the species as the longest-lived vertebrate on record. That single animal, roughly five meters long, would have been born centuries ago and still been swimming when researchers examined it. The finding pushed the known ceiling for vertebrate longevity far beyond that of any other fish, mammal, bird, reptile or amphibian, into a range previously associated only with certain clams and deep-sea corals.

The scale of those ages also reframed everything else about the species. A shark that lives for centuries experiences the ocean on a timescale that dwarfs a human life, quietly outlasting entire eras of history.

Old enough to predate the Mayflower

The centuries-old estimate is exactly why a Greenland shark alive today could reach back to before the Mayflower’s 1620 crossing. The radiocarbon method does not return a single exact year but a most-likely age surrounded by a wide margin of uncertainty, and for the oldest shark that margin ran to more than a century in either direction. At the upper end of that range, the animal could have been born in the 1500s, generations before the Pilgrims set sail, while even the central estimate places its birth in the same era. Because the largest individuals of the species are still out there in the Arctic, it is entirely plausible that some sharks now gliding beneath the ice were alive during the seventeenth century, though the imprecision of the dating means no one can point to a specific animal and name its birth year with confidence.

Why the Greenland shark lives so long

Extreme longevity in this species appears to be a product of the cold and the slow life it enforces. Greenland sharks inhabit frigid, deep Arctic and North Atlantic water, where temperatures hover near freezing, and their metabolism runs at a correspondingly glacial pace. Researchers have noted that the sharks grow only about a centimeter per year, a crawl that helps explain how an animal reaching several meters in length could take centuries to get there. Slow growth comes paired with extraordinarily late maturity: females are estimated to reach reproductive age at somewhere around 150 years, meaning a Greenland shark may not breed until it has already outlived any human. In a stable, cold, low-energy environment, that unhurried pace seems to translate into a life measured in generations rather than decades.

A slow life with modern vulnerabilities

The same biology that grants such long lives also leaves the species exposed. An animal that takes a century and a half to reproduce cannot recover quickly from losses, which makes Greenland sharks acutely vulnerable to being caught accidentally in fishing gear targeting other species. Many carry parasites that attach to their eyes, leaving them effectively near-blind, though in the lightless depths where they hunt and scavenge, vision matters less than a keen sense of smell. Historically the sharks were harvested for their liver oil, and today the main pressure comes from bycatch in industrial fisheries. Protecting a creature that measures its life in centuries requires thinking on a timescale most conservation planning is not built for, since a population depleted now might take hundreds of years to rebuild the oldest, largest animals that make the species so remarkable.

This article was produced with AI assistance and reviewed by Morning Overview editors.

More from Morning Overview