A Greenland shark can live for centuries, outlasting entire human dynasties

A shark cruising through the black, near-freezing water off Greenland today may already have been alive when sailing ships still ruled the seas. Marine biologists now consider the Greenland shark the longest-lived vertebrate on the planet, a slow, secretive predator whose potential lifespan dwarfs that of nearly every other animal with a backbone. Working out just how old these sharks get took decades of frustration and, eventually, a technique borrowed from nuclear physics. The answer reshaped what scientists thought was biologically possible for a fish.

A Predator Built for the Coldest Water on the Planet

The Greenland shark, known to science as Somniosus microcephalus, patrols the frigid waters of the North Atlantic and Arctic Ocean, favoring temperatures that hover between roughly minus 2 and 7 degrees Celsius. It can grow to about 6.5 meters in length and approach 900 kilograms in weight, making it one of the largest shark species alive, rivaling a great white in bulk even though almost nobody ever encounters one. Its sluggish swimming style, eyes often clouded by parasitic copepods, and preference for deep, lightless water have earned it the nickname “sleeper shark.”

That combination of an extreme cold habitat and a body built to conserve energy appears central to its longevity, according to a profile from the Smithsonian’s Ocean Portal, which describes the species surviving in some of the coldest, darkest water in the ocean while barely moving faster than a drift current.

How Radiocarbon-Dating an Eyeball Solved a Decades-Old Mystery

For most fish, researchers estimate age by counting growth rings preserved in hard tissue such as vertebrae or otoliths, much like counting rings in a tree trunk. Greenland sharks defeated that approach because their cartilage skeletons do not lay down the same kind of readable annual bands. Scientists eventually turned instead to the lens of the eye, a structure made of proteins that form before birth and are never replaced or metabolized afterward, effectively locking in a chemical record of the year the shark was born.

By radiocarbon-dating that lens tissue in sharks caught incidentally in fishing nets, researchers concluded the species can live somewhere between 250 and 500 years, a range documented on the shark’s species page. That estimate makes the Greenland shark, by a wide margin, the longest-lived vertebrate ever documented, surpassing long-lived whales and giant tortoises that had previously held the title among backboned animals.

A Metabolism Running in Extreme Slow Motion

Longevity on that scale lines up with a life lived almost entirely in slow motion. Greenland sharks grow at a rate of roughly one centimeter a year, among the slowest growth rates recorded in any shark species, and researchers estimate that females may not reach sexual maturity until they are around 150 years old. A shark born before the United States existed as a country could, by that measure, still not have reproduced by the time steam power began replacing sails at sea.

Why the 250-to-500-Year Estimate Still Has a Wide Margin

That range is wide because radiocarbon dating of eye-lens proteins works best when it can be cross-checked against a known reference point, such as the spike in atmospheric carbon-14 left behind by mid-twentieth-century nuclear weapons testing. Sharks born long before that spike have to be aged using slower-changing background carbon levels, which carries more statistical uncertainty the further back the estimate reaches. Researchers have continued refining the method, but a precise birth year for the oldest individuals sampled so far remains an estimate with real error bars rather than an exact count.

A Longevity Record That Reshuffled the Rankings

Before the eye-lens studies, the longest-lived mammal on record was thought to be the bowhead whale, another cold-water giant that spends its entire life in Arctic and subarctic seas. Research combining chemical aging of the whale’s eye tissue with centuries-old stone and ivory harpoon points recovered from harvested animals put the oldest confirmed bowhead at 211 years, according to findings summarized by the Geophysical Institute at the University of Alaska Fairbanks. That figure had stood as one of the more remarkable longevity claims among mammals for years.

The Greenland shark estimate does not just match that record, it potentially doubles or triples it. Because sharks are not mammals, the bowhead and the Greenland shark do not compete for the exact same title, but taken together the two findings point to a pattern: extreme cold, slow metabolism, and a life spent almost entirely in dark, frigid water appear to be a recipe for extraordinary vertebrate longevity, regardless of which branch of the animal family tree the species belongs to.

From Liver-Oil Hunts to Modern Bycatch

Despite that extraordinary lifespan, the species has not been free of human pressure. Its oil-rich liver made it a target for commercial hunting that peaked in the early-to-mid twentieth century, before synthetic lubricants reduced demand and the practice largely faded out. Today the more pressing threat comes from bycatch, with Greenland sharks caught unintentionally in trawl, longline, and gillnet fisheries operating across the Arctic Ocean, Canada, and the northern United States.

Because the species takes so long to mature, any population recovery from a sustained decline would likely unfold over centuries rather than years or decades. A fish that can wait a century and a half just to begin reproducing has little margin for error once its numbers drop, which is part of why an animal capable of outlasting human dynasties remains vulnerable to something as ordinary as a single season’s fishing gear.

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

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