Why Scientists Think a Shark Could Be 400 Years Old

Could a Greenland shark live for nearly 400 years? Scientists found a clue in the centre of its eye, and a radioactive marker left by nuclear weapons tests. This documentary follows the evidence behind the famous age estimate. Researchers studied the eye lenses of 28 female Greenland sharks. The largest was estimated to be 392 years old, with an uncertainty of ±120 years. How did they reach that number, and what can it actually tell us about the shark’s life? The underwater Greenland shark footage shows the species, not the individual examined in the age study. Some visuals are illustrations or reconstructions. Research: Nielsen et al. (2016), “Eye lens radiocarbon reveals centuries of longevity in the Greenland shark”; COSEWIC (2025), Greenland Shark status report. Footage and archive: NOAA Ocean Exploration, Northeast U.S. Canyons Expedition 2013 (Greenland shark and expedition footage); NOAA Ocean Exploration, Deep Connections 2019 (midwater footage); The Hidden Ocean 2016: Chukchi Borderlands / Oceaneering-DSSI (Arctic icebreaker and deep-sea life); Caitlin Bailey / GFOE / The Hidden Ocean 2016: Chukchi Borderlands (research trawling); U.S. Department of Energy / Wikimedia Commons (Castle Bravo archive footage). The Deep Register explores the evidence and mysteries of life beneath the surface.