Somewhere a kilometer below the surface of the North Atlantic, in waters just above freezing, a shark is drifting. A copepod hangs from his cornea like a tattered streamer. The eye behind that dirty lens still works, more or less, and has for a very long time.
The animal may have been alive at the time of Isaac Newton. The oldest individual ever radiocarbon dated, a five-meter female, was estimated to be 392 years old, with a wide range of uncertainty. This makes Somniosus microcephalus the longest-lived vertebrate known to science, according to the landmark 2016 study dating lens proteins from Greenland shark eyes.
The animal is built for time, not speed.
How can a shark be 400 years old?
Greenland sharks grow slowly. They reach sexual maturity around 150 years old. They move through cold waters near freezing, often at great depths below the surface, and every part of their physiology seems tuned to slow. The 400-year estimate results from an unusual workaround: These sharks lack the calcified vertebrae and otoliths that scientists often use to age fish. So a team led by Danish marine biologist Julius Nielsen turned to the eye. The lens nucleus of a Greenland shark is laid down before birth and is never replaced. Radiocarbon date the proteins in the center of this lens and you get a window into when the shark was an embryo.
When they applied the method to Greenland sharks, they discovered something surprising. The youngest mature adults were already over a century old. The largest female in the study was estimated to be 392 years old, with a 95.4% probability ranging from 272 to 512 years old. Although she was toward the younger end of that range, she belonged to a world that began before modern science had a name.
The parasite on the cornea
Greenland sharks are famous not only for their age, but also for their eyes. In Greenland waters, their corneas are frequently parasitized by Ommatokoita elongata, a copepod that attaches to the surface of the eye. The parasite can swing like a tattered streamer, becoming the shark’s most distinctive feature in close-up.
For decades, the hypothesis was simple. The sharks lived in near-total darkness anyway. The copepods scratched and obscured their corneas. Many believed that vision was degraded enough to be almost irrelevant, replaced by other senses such as smell and lateral line.
This hypothesis is now called into question.
The eyeball on dry ice
A recent study has changed part of the story. Researchers from the University of Basel and the University of California, Irvine examined the eyeballs of ten Greenland sharks caught off the coast of West Greenland between 2020 and 2024. According to research co-author Emily Tom, receiving samples of shark eyeballs was a striking experience, as reported by Smithsonian Magazine.
What the team discovered contradicts a century of assumptions. The light-sensitive parts of the old eyes showed no obvious signs of degeneration. The parasites, although found on the cornea, do not appear to destroy the underlying retina. Sharks, even over 100 years old, still seemed able to see in the limited way their environment allows them.
So are they blind? Not quite. Sharks don’t appear to have high-resolution vision, according to physiologist Dorota Skowronska-Krawczyk of UC Irvine. They can detect light and darkness, but probably not fine shapes or rapid movements. The best description is not blind, but visually limited: the cornea may be scarred and clouded, while the retina behind it remains remarkably intact.
The DNA repair machinery
The reason may be genetic. The Basel and Irvine team focused on genes associated with DNA repair, including ERCC1 and ERCC4, which encode proteins involved in repairing damaged DNA. Greenland sharks showed high expression of ERCC4 in their retina compared to other sharks.
Comparative neurobiologist Laura Ryan of Macquarie University noted that high expression of DNA repair genes could provide a molecular mechanism for maintaining retinal health over centuries, as reported by the Australian Broadcasting Corporation. The same general logic of repair can help explain why an animal that lives so long doesn’t simply accumulate catastrophic cellular damage along the way.
Photo by Magda Ehlers on Pexels
Read the entire genome
In 2026, a team led by Shigeharu Kinoshita of the University of Tokyo published the first whole genome sequence of a Greenland shark in PNAS. The study, published May 19 and reported by Live Science, covered 96.7 percent of the animal’s DNA and highlighted several interlocking systems that could help explain how a vertebrate survives for centuries.
Histone linker proteins, which compact DNA into chromosomes, carry unique amino acid substitutions in Greenland sharks. The likely effect is a more stable chromatin structure, which could help slow the accumulation of DNA damage over time. Gene families related to immune response and DNA repair are expanded. Ferritin genes, which regulate iron storage and protect against oxidative stress, are notably amplified.
According to Kinoshita, extreme longevity appears to result from coordinated changes in multiple biological systems rather than a single genetic factor: genome stability, iron metabolism, immune function, stress resistance. All of this accumulated into one animal moving slowly through the cold water.
What the shark eats as it ages
Greenland sharks are opportunistic to a degree that sometimes borders on the surreal. They eat fish and seals, but they also hunt. Researchers have found remains of land animals such as reindeer, horses, and polar bears in their stomachs; animals that likely drowned, fell through the ice, or eventually fell into the dark world of the shark.
This dietary opportunism adapts to the energy budget. A slow-moving shark cannot hunt every meal in open water. One theory is that they ambush sleeping or vulnerable seals, drifting beneath them in the darkness. Or they wait. Things die. Things flow. The shark is here.
Skepticism, and a rare Irish stranding
Not all scientists accept the clearest version of the 400-year estimate. Aaron MacNeil, a biologist at Dalhousie University, noted that radiocarbon dating relies in part on fallout from Cold War nuclear bombs reaching the depths of the sea, and that mixing in the cold layers of the abyss may have been slower than the initial calibration assumed. In other words, the age estimates might be somewhat inflated. MacNeil told Live Science that while exact estimates have uncertainties, sharks are still definitely very old: at least 200 years old.
The mystery of the species sometimes surfaces in a literal way. In April 2026, a rare Greenland shark washed up on the coast of County Sligo in Ireland, the first recorded stranding of the species on the Irish coast. The animal was recovered by the National Museum of Ireland, a rare opportunity to study a deep-sea animal that typically lives well beyond ordinary human reach.
The years of liver oil
One reason there are no very old Greenland sharks left is that humans spent the 19th and early 20th centuries hunting them industrially for their liver oil. Because sharks reproduce so slowly and mature so late, the population has been slow to recover. Some marine biologists believe it is still recovering from the hunt that effectively ended decades ago.
Today, many encounters are accidental, often in the form of bycatch in deep-sea fisheries. Their habitat, black, near-freezing water far below the surface, keeps them mostly out of human reach. It’s one of the few benefits of living somewhere humans don’t want to go.
What it means to watch one
The numbers, taken together, describe an animal operating at a different pace than almost all other vertebrates. Growth is of the order of one centimeter per year. Sexual maturity occurs around the age of 150. The radiocarbon estimate of 392 years has a 95.4% probability range of 272 to 512 years, an interval wide enough to encompass most of recorded modern history. Even MacNeil’s more conservative reading still places the oldest individuals at 200 years or older.
The method behind these numbers boils down to a small amount of protein in the center of a lens, fixed in place before the shark was born, then read against a baseline calibrated in part from the nuclear fallout of the mid-20th century. Genome sequencing adds a parallel set of evidence: amplified ferritin genes, expanded DNA repair families, altered linker histones, elevated ERCC4 expression in the retina.
None of this is poetic. This is exactly what the fabric shows when measured.
For more detailed information, visit the original article here.
“`
