Somewhere in the frigid depths of the North Atlantic and Arctic Ocean, a shark alive today could have been swimming before the first European colonists ever set foot in North America. That is not exaggeration for effect; it is the conclusion of researchers who found a way to estimate the age of an animal with no bones, no growth rings, and almost no hard tissue anywhere in its body. The species is the Greenland shark, and its lifespan may be the longest of any vertebrate on Earth.
A Body With No Clock to Read
Scientists had long suspected Greenland sharks lived unusually long lives, but for decades they had no reliable way to prove it. Most sharks can be aged by counting growth bands on their fin spines or vertebrae, similar to counting rings on a tree trunk. Greenland sharks have neither hard fin spines nor bones capable of forming those bands, so researchers could only infer old age indirectly, from the fact that the species grows less than a centimeter a year yet can reach more than six meters in length, according to the National Oceanic and Atmospheric Administration.
Carbon-Dating an Eye Instead of a Tree Ring
The breakthrough came from an unlikely body part: the shark’s eyes. Proteins inside the lens of a Greenland shark’s eye form before birth and never break down or get replaced afterward, effectively preserving a biological time capsule at the center of each eye, similar to a fossil trapped in amber. By radiocarbon-dating the innermost layer of that lens, scientists can pin down roughly when an individual shark was born. Researchers applied the technique to Greenland sharks caught incidentally as bycatch in fishing nets, and the largest animal in the sample, a five-meter female, was estimated to be somewhere between 272 and 512 years old, per NOAA. Even the low end of that range, 272 years, was enough to make the Greenland shark the longest-lived vertebrate known to science, a finding first published in the journal Science in 2016.
Because radiocarbon dating produces a range rather than an exact figure, researchers describe the shark’s age as an estimate that could be refined as the method improves, not a precise birth date. Still, NOAA notes that scientists now put the species’ minimum lifespan at roughly 250 years, with some individuals potentially surviving past 500. Researchers involved in the original study have said they expect the method to be refined further as more eye lenses are sampled, which could eventually narrow the wide range currently attached to the oldest individuals.
The dating method only works because the sharks examined were already dead, caught incidentally in survey nets rather than targeted deliberately, which is part of why researchers describe the resulting age estimates as an unusually rare scientific opportunity rather than a routine measurement. Repeating the analysis on a larger number of animals, drawn from different parts of the shark’s Arctic and North Atlantic range, is the most likely path to tightening the current estimate.
Life in the Slowest, Coldest Lane of the Ocean
One leading explanation for the shark’s extraordinary longevity is an equally extraordinary metabolism. Greenland sharks live in some of the coldest water on the planet and have adapted by slowing nearly everything down. A NOAA remotely operated vehicle exploring off New England once encountered a Greenland shark at a depth of 783 meters, and the species is known to dive as deep as 2,200 meters, making it the only shark that can tolerate the Arctic Ocean’s cold year-round. That sluggish chemistry also caps the animal’s speed at under 2.9 kilometers per hour, roughly a brisk human walking pace, and researchers believe the same slow metabolism that limits its growth and movement is what allows its cells to avoid the wear and tear that ages faster-living animals.
A Species That Takes a Century to Grow Up
The shark’s slow-motion biology has consequences well beyond its own lifespan. Because Greenland sharks grow so gradually, researchers believe they are not thought to reach sexual maturity until they are more than 100 years old. That single fact reshapes how the species should be managed: removing a mature, reproductively active Greenland shark from the ocean can affect the population and surrounding ecosystem for decades afterward, since a replacement animal takes a full human lifetime or more to reach breeding age. Greenland sharks were once hunted commercially for their liver oil, but most that end up in fishing gear today are caught unintentionally, which is why reducing bycatch has become central to conserving the species.
Longevity That Complicates Conservation
The combination of a centuries-long lifespan and a century-long adolescence makes the Greenland shark unusually vulnerable to even modest fishing pressure, since population recovery after a decline could plausibly take longer than a human generation to measure. It also means that a shark caught today, examined, and released could be carrying genetic and physiological information about ocean conditions from the 17th or 18th century, long before industrial fishing, modern shipping, or measurable ocean warming began reshaping the Arctic and North Atlantic. For researchers, that makes every sampled Greenland shark less like a single data point and more like a living archive of centuries of ocean history, still swimming through the same cold water it was born into.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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