Somewhere in the cold, dark waters off Greenland, sharks alive today may have been swimming before the founding of the United States, before the invention of the telescope, and in at least one estimated case, before Shakespeare finished writing his plays. That is not exaggeration for effect. It is the conclusion of a peer-reviewed study that used radiocarbon dating to measure the age of Greenland sharks and found the species likely holds the record for longest lifespan of any vertebrate on Earth.
Measuring how long a wild animal actually lives is far harder than it sounds, since there is rarely a birth certificate or a tagging record stretching back centuries. Scientists studying long-lived species have long relied on indirect methods, counting growth rings in shells or bones, tracking known individuals over a researcher’s own career, or, in this case, reading a chemical signature locked into tissue that never changes after it forms. The Greenland shark’s age estimate stands out because the method behind it can be checked against an independent, well-dated event in recent history rather than relying on assumptions about growth rates alone.
How radiocarbon dating an eye can reveal an animal’s age
The technique behind the discovery relies on a quirk of shark eye anatomy. The center of a Greenland shark’s eye lens forms before birth and never changes afterward, meaning the chemical composition locked into that tissue reflects conditions from the exact year the shark was born rather than its current age. Researchers led by Julius Nielsen at the University of Copenhagen measured levels of carbon-14 in the lens nuclei of 28 female Greenland sharks, ranging from about 81 to 502 centimeters in length, and cross-referenced the readings against a well-documented spike in atmospheric carbon-14 caused by nuclear weapons testing in the 1950s. That spike works like a dateable marker embedded in the tissue, letting scientists calculate roughly when each shark’s eye lens formed, according to the original study published in Science under the title “Eye lens radiocarbon reveals centuries of longevity in the Greenland shark”.
Why the largest shark measured came out at nearly 400 years old
The largest animal in the sample, at 502 centimeters, or roughly 16.5 feet, long, was estimated to be 392 years old, with a margin of error of plus or minus 120 years. That range means the shark’s true age could fall anywhere from about 272 to 512 years, and even the lower bound of that range would still make it the longest-lived vertebrate species documented, surpassing bowhead whales, which had previously held that title with lifespans estimated around 200 years. The study’s authors were careful to frame their headline number as a best estimate with substantial uncertainty rather than a precise figure, a nuance that has often been flattened in the years since into the simpler claim that Greenland sharks can live 400 years, a summary reflected in outlets including ScienceDaily’s coverage of the findings.
A species that barely grows and takes a century to mature
What makes such extreme longevity biologically plausible is the Greenland shark’s exceptionally slow metabolism and growth rate, adaptations to the frigid, food-scarce Arctic and North Atlantic waters it inhabits, often at depths exceeding half a mile. The same study estimated that female Greenland sharks do not reach sexual maturity until at least 156 years of age, give or take 22 years, meaning a shark could swim for a century and a half before ever reproducing. That slow-motion life history, growing roughly a centimeter per year according to earlier tagging studies, is consistent with the multi-century lifespan the radiocarbon data implied, since an animal built to grow that slowly would need a correspondingly long life to reach the sizes researchers regularly observe.
A body built for the cold that comes with its own hazards
Much of what makes a multi-century lifespan biologically plausible also comes bundled with stranger traits. The shark’s flesh carries high concentrations of urea and trimethylamine oxide, compounds that likely help its cells resist the crushing pressure and near-freezing temperatures of its deep, cold habitat, but that make the meat toxic if eaten fresh. In Iceland, that flesh has long been fermented and wind-dried for months to break down those compounds, producing a traditional dish called hakarl that remains part of Icelandic food culture today, a practice that predates any scientific understanding of why raw Greenland shark meat could otherwise cause serious illness. Most Greenland sharks also carry a parasitic copepod attached to each cornea, a hitchhiker that likely leaves the shark partially blind, though the species appears to compensate by hunting primarily through smell and by detecting vibrations from injured or vulnerable prey rather than relying on eyesight.
Why body size, not just age, matters for the record
Greenland sharks are also physically massive, regularly reaching lengths beyond 5 meters, or more than 16 feet, which put the study’s largest specimens close to the upper size range recorded for the species. Larger, older individuals are harder to sample than smaller ones, since Greenland sharks are typically caught as bycatch rather than targeted for study, which is part of why the 2016 dataset, drawn from sharks caught incidentally in fishing nets across the species’ range, represented a rare opportunity to apply radiocarbon dating across a wide range of body sizes and, by extension, ages. Background on the species’ size, range, and slow biology is compiled on the Wikipedia entry for Greenland shark.
What the record means for how the species is protected
A lifespan measured in centuries carries direct consequences for how vulnerable a species is to overfishing, since a Greenland shark population that loses breeding-age adults, animals that took a century and a half just to reach maturity, cannot realistically recover on any timescale relevant to fisheries management or human policy. That reality has shaped how conservation scientists talk about the species today, treating individual adult Greenland sharks as effectively irreplaceable on human timescales even though the species as a whole is not currently classified as endangered. The 2016 findings remain the foundational evidence behind that framing nearly a decade after the study’s publication, cited repeatedly whenever researchers discuss which animals hold the outer limits of vertebrate longevity.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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