In the deep waters of the Arctic and North Atlantic, the Greenland shark lives on a timescale that is difficult to observe directly. It grows by only a small amount each year, can exceed five meters in length and may survive for several centuries.
The number most often attached to the species is 400 years. It comes from a 2016 radiocarbon study that estimated the largest shark in its sample at 392 years old. The uncertainty was enormous: the 95.4 percent probability range stretched from about 272 to 512 years.
The 150-year age of “adulthood” also needs translation. Researchers were estimating sexual maturity, not a distinct developmental birthday they had observed. The result was inferred by combining the size at which females become reproductively mature with an estimated relationship between body length and age.
Even with those qualifications, the underlying biology is exceptional. The evidence supports a lifespan of at least 272 years, longer than any other vertebrate documented so far, and suggests that female Greenland sharks may spend well over a century growing before they reproduce.
A shark with no convenient annual clock
Biologists often age fish by counting repeated growth bands in hard structures, rather as dendrochronologists count tree rings. Sharks are difficult because their skeletons are made primarily of cartilage. Some shark vertebrae contain bands that can be used, but the technique must be validated for each species because a band does not necessarily represent one year. NOAA Fisheries explains why modern shark-ageing work increasingly tests several tissues and chemical markers instead of assuming that every visible ring is annual.
Greenland sharks present a harder version of the problem. They lack reliable calcified structures that preserve a simple lifetime sequence. They are also rarely encountered when young, live in remote and often deep water, and cannot be followed from birth for anything close to their suspected lifespan.
Julius Nielsen of the University of Copenhagen and colleagues found a clock in the center of the eye lens. The lens nucleus contains proteins formed during embryonic development. Unlike most living tissue, those proteins remain largely metabolically inert, so the carbon incorporated into them provides information about the animal’s earliest life.
Cold War carbon helped anchor the age model
For their 2016 study in Science, Nielsen and his co-authors measured radiocarbon in the eye-lens nuclei of 28 female Greenland sharks ranging from 81 to 502 centimeters long. The animals had been caught as fisheries bycatch, so this was not a study in which known living sharks were tagged and revisited centuries later.
Radiocarbon, or carbon-14, decays at a known rate. But dating a marine animal is not as simple as reading that decay against the atmosphere. Carbon moves slowly and unevenly through the ocean, and the age of carbon in a shark’s food can differ from the carbon in air during the same year. The researchers therefore needed calibration data and a statistical model that included marine reservoir effects.
Atmospheric nuclear-weapons tests in the 1950s and 1960s supplied one useful marker. They sharply increased carbon-14 in the environment, creating the “bomb pulse.” The three smallest sharks in the sample showed evidence of this modern radiocarbon signal, confirming that they were born after the pulse entered the marine food web. Larger sharks lacked it and were older.
The team then combined the radiocarbon results with shark length in a Bayesian age model. The conclusion was not that every animal of a given size has an exact age. It was a probability distribution linking larger bodies to much longer lives, with uncertainty increasing markedly for the oldest animals.
The oldest estimate came with a 240-year span
The largest specimen measured 502 centimeters and had a midpoint age estimate of 392 years. The reported uncertainty was plus or minus 120 years at the 95.4 percent probability level. Put plainly, the model placed this shark somewhere between roughly 272 and 512 years old.
The second-largest shark, at 493 centimeters, was estimated at 335 years, again with a wide range. From the full analysis, the authors concluded that Greenland sharks have a lifespan of at least 272 years.
This is why “can survive for roughly 400 years” is a reasonable popular summary but not a measured maximum lifespan. The midpoint for one very large shark was close to 400. The lower and upper bounds were separated by more than two centuries, and the study did not observe a natural death from old age.
The estimate has not been independently repeated across a large new sample. Canada’s comprehensive 2025 Greenland shark status report notes that the 28-shark analysis remains the single direct ageing study for the species. It treats the available evidence as support for remarkable longevity while emphasizing how limited the age and growth data remain.
Reaching adulthood means becoming able to reproduce
The 2016 paper estimated that sexual maturity occurs no earlier than roughly 156 years, expressed as 156 plus or minus 22 years. That figure did not come from an anatomical examination of a known 156-year-old shark. Researchers already had an approximate female length at maturity of around four meters. They used their age-length model to estimate how long it would take to reach that size.
Newer reproductive work has refined the size threshold. In a 2020 study in PLOS ONE, researchers examined reproductive organs from 312 Greenland sharks collected over several decades. They estimated that half of females were mature at a length of 419 centimeters. Combining that result with the 2016 age model suggested females reach sexual maturity no earlier than 134 years.
Those estimates are compatible with the familiar “around 150” shorthand, but the uncertainty matters. Growth may differ among individuals, sexes, locations and periods of life. The 2020 authors also stressed how little is known about pregnancy and pupping. Even the species’ gestation time remains unsettled.
“Adulthood” can imply a broad life stage. Here the measurable question is narrower: when the reproductive organs indicate that a shark is capable of breeding. A Greenland shark can be a large, decades-old animal and still be biologically immature by that definition.
Did any living shark predate the steam engine?
Thomas Savery received a patent for an early steam-powered water pump in 1698. The Linda Hall Library’s history of Savery also documents his demonstration of a model to the Royal Society the following year. Thomas Newcomen’s commercially successful atmospheric engine followed around 1712.
A shark alive in July 2026 would need to be more than 328 years old to have been swimming before Savery’s patent. The Greenland shark age model makes that biologically plausible. Its midpoint estimate for the largest specimen easily clears that threshold, and even the second-largest specimen had a midpoint age of 335 years.
But the comparison is an inference about the population, not a verified biography of a living animal. All 28 sharks used in the radiocarbon study were dead when their eye lenses were collected. No known shark alive today carries a precise birth date showing that it predates 1698. Photographs shared online with claims of a specific 17th-century birth year usually show an unidentified shark, not the dated specimen.
The careful statement is that some Greenland sharks alive today may have been born before the first practical steam-powered devices. The evidence supports the necessary lifespan, but researchers cannot point to an individual and prove it.
Living slowly in cold water is not a complete explanation
Greenland sharks inhabit cold waters across the Arctic and North Atlantic and are found from relatively shallow areas to depths of more than two kilometers. Low temperature and slow growth fit a general “slow pace of life,” but neither fact by itself explains a four-century lifespan. Other cold-water fishes do not necessarily live for centuries.
The biology behind that longevity is now being investigated at several levels. Researchers are examining metabolism, heart function, DNA repair, immune pathways and the maintenance of tissues such as the eye. A 2026 Greenland shark genome study in Proceedings of the National Academy of Sciences identified features that may be relevant to genome stability and cellular maintenance.
These are candidate mechanisms, not a solved explanation. A large genome or an expanded family of repair-related genes does not by itself show which processes extend life, how strongly they act or whether the same mechanisms would matter in another species. Functional experiments are still needed.
Longevity creates a conservation liability
A centuries-long life can sound like protection against extinction. In population terms, very late maturity can do the opposite. If females need more than a century before reproducing, removing mature animals can create a gap that takes longer than a human lifetime to replace.
Greenland sharks were historically caught in large numbers for liver oil. Targeted fisheries have largely ended, but the sharks are still taken accidentally in fisheries operating in northern waters. Their slow life history makes the consequences difficult to measure quickly. A population can continue to contain large adults even while too few young animals are surviving to sustain it.
Canada designated the species as Special Concern in 2025. The assessment cited bycatch, climate-driven habitat changes, pollution and limited biological knowledge among the reasons for caution. Uncertainty about population size does not cancel the risk created by slow growth and delayed reproduction.
The historical comparison works because the shark’s estimated life can contain several eras of human technology. The evidence does not give us a 400-year-old individual with a documented biography. It gives us something scientifically more demanding: a probability range built from eye chemistry, ocean carbon and body size, pointing to an animal whose ordinary biology may operate across centuries.