In the frigid depths of the Arctic and North Atlantic, the Greenland shark inhabits an era that is challenging to observe firsthand. It grows at a slow pace each year, can reach lengths exceeding five meters, and may live for centuries.
The age most commonly associated with the species is 400 years. This figure stems from a 2016 radiocarbon study which estimated the oldest shark in its sample to be 392 years old. The uncertainty was substantial: a 95.4 percent probability range extended from around 272 to 512 years.
The 150-year mark for “adulthood” also warrants clarification. Researchers were estimating the age of sexual maturity, not a specific developmental milestone they had directly observed. This inference was drawn by correlating the size at which females achieve reproductive maturity with an estimated connection between body length and age.
Despite these qualifications, the underlying biology is remarkable. The findings indicate a minimum lifespan of at least 272 years, surpassing any other documented vertebrate, and suggest that female Greenland sharks may spend over a century maturing before they reproduce.
A shark without a convenient annual clock
Biologists typically age fish by counting the growth rings in dense structures, similar to how dendrochronologists assess tree rings. Sharks pose a challenge because their skeletons are primarily composed of cartilage. Some shark vertebrae feature bands that can be utilized, but the technique must be verified for each species since a band does not necessarily denote a single year. NOAA Fisheries elaborates on why contemporary shark age estimation increasingly examines various tissues and chemical markers, rather than assuming every observable ring is annual.
Greenland sharks complicate the issue further. They have no dependable calcified structures that maintain a straightforward lifetime timeline. Furthermore, they are infrequently encountered in their younger stages, inhabit remote and often deep waters, and cannot be tracked from birth throughout the entirety of their suspected lifespan.
Julius Nielsen from the University of Copenhagen and his team discovered a clock within the eye lens. The nucleus of the lens comprises proteins developed during embryonic growth. In contrast to most living tissue, these proteins remain significantly metabolically inactive, meaning that the carbon they contain reveals information regarding the animal’s earliest existence.
Cold War carbon helped establish the age model
In their 2016 study published in Science, Nielsen and colleagues analyzed radiocarbon levels in the eye-lens nuclei of 28 female Greenland sharks, which ranged from 81 to 502 centimeters in length. These sharks were captured as bycatch in fisheries, thus it was not a study involving tagged living sharks revisited centuries later.
Radiocarbon, or carbon-14, decays at a predictable rate. However, dating a marine organism is not as straightforward as simply tracking that decay against the atmosphere. Carbon travels slowly and unevenly through the ocean, and the age of carbon in a shark’s diet can vary from the carbon in the air during the same year. Consequently, the researchers required calibration data and a statistical framework that considered marine reservoir effects.
Atmospheric nuclear weapons tests conducted in the 1950s and 1960s provided a beneficial marker. These tests caused a dramatic rise in carbon-14 levels in the environment, generating the “bomb pulse.” The three smallest sharks in the sample exhibited signs of this modern radiocarbon signal, confirming their birth after the pulse infiltrated the marine food web. Older sharks did not show this signal.
The research team then integrated the radiocarbon findings with shark size in a Bayesian age model. The conclusion was not that each animal of a specific size possesses an exact age. Instead, it illustrated a probability distribution connecting larger individuals to significantly longer lifespans, with uncertainty increasing notably for the oldest specimens.
The oldest estimate came with a 240-year range
The largest specimen measured 502 centimeters with a midpoint age estimate of 392 years. The reported uncertainty was plus or minus 120 years at the 95.4 percent probability level. In simple terms, the model suggested this shark was aged between approximately 272 and 512 years.
The second-largest shark, measuring 493 centimeters, was estimated to be 335 years old, again with a broad range. From the overall analysis, the authors concluded that Greenland sharks likely have a lifespan of at least 272 years.
This is why saying they “can survive for approximately 400 years” serves as a plausible popular summary but not a definitive maximum lifespan. The midpoint for one extremely large shark was near 400. The lower and upper limits spanned over two centuries, and the study did not document any natural death attributable to old age.
The estimate has not been independently replicated on a larger new sample. Canada’s comprehensive 2025 report on Greenland sharks acknowledges that the analysis involving 28 sharks remains the sole direct age study for the species. It regards the existing evidence as supportive of exceptional longevity while highlighting the limitations of the age and growth information.
Reaching adulthood signifies the ability to reproduce
The 2016 research estimated that sexual maturity occurs no sooner than approximately 156 years, expressed as 156 plus or minus 22 years.