A shark swimming today may have been born before the United States existed

Somewhere in the frigid dark of the North Atlantic, a shark alive right now may have already been swimming for centuries before the first American flag was raised. That is not a metaphor. It is the working conclusion of scientists who study the Greenland shark, a slow-moving, deep-water predator that appears to live longer than any other vertebrate on record.

The claim sounds like folklore, the kind of fish tale that grows a little with each telling. But it rests on a genuinely novel piece of biochemistry, one that let researchers do something no one had managed before: put a real number on the age of an animal that leaves behind none of the usual clues.

Why counting rings does not work on this shark

Most sharks can be aged the way foresters age trees. Bony structures such as fin spines or vertebrae lay down growth bands year after year, and biologists count the rings. The Greenland shark ruins that trick. It has no fin spines, and its vertebrae are too soft and cartilaginous to hold a clean, countable pattern the way a mako or a great white’s does. For decades, that left researchers with only indirect evidence: the species grows less than a centimeter a year, yet individuals reach more than six meters in length. Simple arithmetic implied a lifespan measured in centuries, but nobody could prove it.

An eye-lens shortcut around the missing growth rings

The breakthrough came from an unlikely structure inside the shark’s eye. The lens contains proteins that form before birth and then stay chemically inert for the rest of the animal’s life, never being replaced or metabolized. That stability means the carbon inside those lens proteins is frozen in time, effectively dated to the moment the shark was born. Researchers at NOAA note that scientists began radiocarbon-dating those lens cores, treating them the same way archaeologists date organic material recovered from ancient sites. Applied to Greenland sharks caught as accidental bycatch in northern fishing nets, the method produced startling results. According to NOAA’s summary of the research, the largest shark examined, a five-meter female, was estimated at somewhere between 272 and 512 years old.

A margin of error that still rewrites the record book

Radiocarbon dating of biological tissue is never exact, and the Greenland shark study carries a wide range because the technique measures probability, not a fixed birth certificate. Even taking the conservative end of that range seriously changes the record. A minimum lifespan of roughly 272 years would still make the Greenland shark the longest-lived vertebrate identified so far, comfortably ahead of the bowhead whale, previously the species credited with the longest vertebrate lifespan at around two centuries. Scientists studying the animal continue to refine the dating method, and NOAA notes that more precise measurements may eventually narrow the estimate. But the basic conclusion, that this species can live for multiple human lifetimes, has held up.

A slow metabolism built for the cold and the dark

The leading explanation for such extreme longevity traces back to where the shark lives. Greenland sharks inhabit the Arctic and North Atlantic, often at crushing depths; NOAA has documented one encountered at 783 meters, and the species is known to dive past 2,200 meters. Water at those depths hovers barely above freezing year-round, and the shark appears to have adapted with an unusually slow metabolism. That sluggish internal engine likely explains several of its other traits at once: glacial growth, a top swimming speed under 3 kilometers per hour, and, researchers suspect, a correspondingly slow pace of cellular aging. It is the same broad principle seen in other cold, slow-metabolism animals that outlive their warmer, faster relatives, just taken to an unusually extreme conclusion.

Centuries to reach adulthood changes the conservation math

Longevity like this is not simply a curiosity for a nature almanac. NOAA points out that because Greenland sharks grow so slowly, they likely do not reach sexual maturity until they are well over a century old. A shark caught as bycatch today, whether intentionally or not, may be an animal that has not yet reproduced even once, despite already having outlived every human being who has ever handled it. Removing mature individuals from the population, even in small numbers, can therefore echo through the species for far longer than it would for a fish that matures in a handful of years. That slow-motion vulnerability is part of why fisheries scientists have pushed for better bycatch-reduction measures specifically aimed at deep-water longline and net fisheries in the shark’s range.

What still is not known

Plenty remains unresolved. Researchers have not pinned down an exact maximum lifespan, only a wide probabilistic band, and the biochemical mechanism that lets the species avoid the usual toll of cellular aging is still under active study. Genomic work on the species, published by outside research groups in recent years, has started probing what its DNA might reveal about extreme longevity more broadly, a question with implications well beyond one shark species in one ocean. For now, the Greenland shark holds its record on the strength of frozen proteins in its eyes, a reminder that some of the animal kingdom’s biggest discoveries hide in the least likely tissue.

This article was produced with the assistance of AI and reviewed by an editor.

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