How an eye lens revealed the Greenland shark’s centuries-long life

A clock hidden in the eye

Determining a Greenland shark’s age had frustrated researchers. Some sharks can be aged from growth bands in their spines or vertebrae. Greenland sharks lack the fin spines and suitably hard vertebrae needed for those approaches, leaving scientists with an animal that grew extraordinarily slowly but no straightforward way to count its years. [2]

The eye offered another route. Proteins at the center of the lens form before birth and remain metabolically inactive. Their chemistry preserves information from the shark’s earliest development, allowing researchers to apply radiocarbon dating to tissue that has stayed largely unchanged throughout its life. The University of Copenhagen team worked with specialists in carbon-14 analysis at Aarhus University. [3]

What “392 years old” actually means

The study analyzed 28 female sharks. For the largest, 392 ± 120 years represents the midpoint and extent of a 95.4% probability range. [1] The resulting 272-to-512-year interval supplies neither an exact birthday nor proof that she reached its upper end. [2]

Only sharks measuring 220 centimeters or less showed the radiocarbon “bomb pulse” associated with early-1960s nuclear testing, providing a marker for younger animals. [1]

NOAA’s explanation emphasizes the same limit: carbon dating provides an estimate, and the method can be refined. The important result survives the uncertainty. Even the low end of the largest shark’s estimated age reaches well beyond two centuries. [2]

A life measured in generations

Female sexual maturity was estimated at at least 156 ± 22 years. This model-based inference combines age estimates and maturity size; it does not describe a shark observed for 156 years. The familiar “about 150” figure carries that qualification. [1]

Such a slow life history matters beyond the record book. NOAA identifies accidental capture in fishing gear as a conservation concern and notes that losing mature animals can affect the species for decades. An animal that takes more than a human lifetime to reach maturity cannot be expected to replace adults quickly. [2]

The Copenhagen researchers collected specimens mainly through accidental bycatch during fish surveys and other research voyages. Their work turned a long-standing suspicion of exceptional longevity into a measurable estimate, while making clear how much remains to be learned about these deep-water sharks. [3]