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A Greenland shark does not look like an animal in a hurry. It moves through cold northern water with the heavy, unbothered patience of something that has no obvious reason to rush. Its body is blunt, grey and thick; its eyes are small; its world is dark, deep and slow.
That slowness has made the shark famous. In 2016, researchers reporting in Science used radiocarbon dating of eye-lens tissue from 28 female Greenland sharks and estimated that the largest animal in their sample was about 392 years old, with a very wide uncertainty range of plus or minus 120 years. Even the cautious reading was astonishing: the species appeared to be the longest-lived vertebrate known.
That is how a fish becomes a time machine. A Greenland shark alive today may have begun life before telescopes were common scientific instruments, before Isaac Newton published his great work on gravity, before modern biology had a name. Depending on where an individual falls within the age estimate, its life could reach back into the early centuries of European colonial settlement in North America.
The headline comparison needs one careful historical footnote. Europeans had reached North America long before the 1600s, including Norse settlement at L’Anse aux Meadows around the year 1000, and Spanish, French and English colonial settlements appeared at different times. The shark’s real power is not that it neatly fits one schoolbook date. It is that one living animal can make the early modern world feel biologically recent.
How do you age an animal that old?
You cannot simply count birthday candles on a Greenland shark. Many fish can be aged by looking at growth rings in hard body parts such as otoliths, the tiny ear stones used in balance and hearing. Sharks do not have bony otoliths, and the Greenland shark’s deep-water life makes long-term observation almost impossible.
The 2016 team used a stranger clock: the lens of the eye. The inner proteins of the eye lens are formed early in life and then remain metabolically stable. By measuring radiocarbon in those tissues, the researchers could look for the chemical signature left by mid-20th-century nuclear bomb testing in the atmosphere, then combine that marker with shark length and growth modelling to estimate age.
The method does not hand back a neat birthday. It gives probabilities, ranges and uncertainty. That is why the most famous number, roughly 400 years, should be read as an estimate rather than a certificate. The oldest shark in the study was not known to have been exactly 392 years old. It was estimated at 392 years, with a range broad enough to place it centuries either side.
But uncertainty is not the same thing as weakness. Even at the lower end of the estimate, the shark was extraordinarily old. The study also suggested that female Greenland sharks may not reach sexual maturity until around 156 years of age. For conservation, that may be the most sobering number in the whole paper.
A life slowed by cold water
The Greenland shark, Somniosus microcephalus, belongs to the sleeper sharks, a name that suits its public image almost too well. The Florida Museum’s species profile describes it as a large, heavy-bodied shark of the North Atlantic and Arctic, commonly associated with cold water, deep habitats and slow swimming.
Cold water changes biology. Chemical reactions run more slowly. Metabolism can slow. Growth can stretch across decades. Greenland sharks are often described as growing at a crawl, adding perhaps about a centimetre a year, though growth estimates remain difficult because the animals are so hard to study directly.
That does not make them helpless. Greenland sharks are apex predators and scavengers. Stomach-content studies have found fish, seals and other animals inside them, and researchers still debate how a famously slow swimmer catches faster prey. One possibility is that the shark ambushes sleeping seals; another is that scavenging plays a larger role than the predator mythology allows.
The animal’s strangeness is easy to exaggerate. It is not a monster from a lost world. It is a living shark adapted to conditions that make human observation difficult: cold, dim water, long distances, deep slopes and a life history stretched so far that our usual animal timelines start to fail.
Four centuries inside one body
The reason the Greenland shark captures attention is not merely the number. Plenty of organisms live a long time if we include clonal plants, corals, sponges and other life forms with unusual definitions of individuality. The Greenland shark is different because it is a vertebrate: an animal with a backbone, a brain, organs and a body plan more immediately familiar to us.
That familiarity makes the age feel almost impossible. A shark born around the early 1600s could have been swimming before the Mayflower crossed the Atlantic, before Galileo’s trial, before the word “scientist” existed. It could have moved through Arctic water while empires rose and fell above the surface, while whaling ships came and went, while industrial fishing turned from sail and hook into engines, steel and sonar.
It would not have experienced that history in any human sense. The comparison is ours, not the shark’s. Still, it helps us understand the scale. A Greenland shark’s life may be long enough to make several human civilizations feel like passing weather.
Extreme age creates extreme vulnerability
Long life can sound like resilience, but in population biology it often comes with fragility. Animals that grow slowly, mature late and reproduce slowly cannot rebound quickly when too many adults are removed. A species whose females may need more than a century to reach reproductive age is not built for rapid recovery.
The IUCN Red List currently treats the Greenland shark as vulnerable. Historically, it was targeted for liver oil in North Atlantic fisheries, and today it can still be caught incidentally. Climate change adds another uncertainty by altering Arctic and sub-Arctic marine systems faster than long-lived animals can easily track.
This is the uncomfortable side of the 400-year fact. A shark that may have survived since the early colonial period could be killed in a single modern fishing event. A population that took centuries to build can be thinned in a few human decades.
What an old shark teaches
Scientists are interested in Greenland sharks for more than novelty. Their longevity raises questions about metabolism, DNA repair, cancer resistance, protein maintenance and the biology of ageing. How does a vertebrate body keep functioning across centuries? What breaks slowly, what stays protected, and what trade-offs come with such a drawn-out life?
Those questions remain open. The Greenland shark is difficult to study precisely because it lives where humans are clumsy visitors. Every new specimen, genetic analysis or deep-sea observation adds to a picture that is still incomplete.
For now, the shark’s most immediate lesson may be about time. Human history feels old to us because we live short lives. Four centuries is enough for nations to form, languages to shift, technologies to transform and maps to be redrawn. To a Greenland shark, if the age estimates are right, that span can fit inside one lifetime.
Somewhere in the cold North Atlantic, an animal may still be moving through the dark with a body that began growing before much of the modern world had taken shape. It is not a fossil. It is not a legend. It is a shark, still swimming, carrying a scale of time that makes our own feel suddenly brief.
