Greenland sharks can live for more than 400 years — meaning some of the ones swimming the North Atlantic today were alive when Isaac Newton was — and almost all of them spend those centuries functionally blind, navigating the deep ocean with parasites permanently attached to their eyes.

The Greenland shark has become a fixture of popular science writing in the way of a small number of charismatic creatures: the immortal jellyfish, the deep-sea tube worm, the bristlecone pine. The story arrives in roughly the same shape each time it is told. The shark lives for centuries. Some of the largest individuals alive in the North Atlantic today may have been born before or during Isaac Newton’s lifetime. Across those centuries, a parasitic copepod attaches to the cornea and stays there. The popular conclusion is that the sharks live extraordinarily long lives, and that they spend almost all of those lives blind.

The first part of that story is well-supported. The second part has just been revised, and the way it has been revised is more interesting than the version it replaces.

We want to look at what happened to the blindness claim, and then at what tends to happen when popular science meets a creature that lives much longer than we do.

The 2016 paper and what it actually said

The longevity claim rests on a single primary source: a 2016 paper in Science by Julius Nielsen and colleagues, based at the University of Copenhagen with a small group of collaborating institutions. The team applied radiocarbon dating to the eye lens nuclei of 28 female Greenland sharks ranging from 81 to 502 centimetres in length. The lens nucleus is useful for this work because it forms during embryonic development and does not turn over the way most tissues do. The carbon-14 captured at the centre of the lens reflects atmospheric carbon-14 at the time of birth.

The result was an estimated lifespan of at least 272 years, with the two largest sharks in the sample dated at approximately 335 and 392 years. The 392-year figure carries a confidence interval of plus or minus 120 years, which the popular version of the story tends to flatten. The reasonable reading is that the species can live for several centuries, that some individuals currently in the population were born in the 1600s or 1700s, and that the precise upper limit remains genuinely uncertain.

The blindness claim has a separate origin. It comes from a series of papers across the 1990s and 2000s describing infection by Ommatokoita elongata, a copepod parasite that attaches to the corneal surface, anchors itself with an adhesive structure called a bulla, and feeds on the tissue. The 1998 paper by Borucinska and colleagues, looking at six infected shark eyes in Victor Bay in the Canadian Arctic, concluded that parasitism “could lead to severe vision impairment, possibly including blindness”. That qualifier “possibly” did most of the work, and it was the part that gradually fell away in summary after summary, until “the sharks are functionally blind” became the standard line.

What the new paper actually shows

In January 2026, Lily Fogg, Dorota Skowronska-Krawczyk and colleagues at the University of Basel and UC Irvine published in Nature Communications what is, in our reading, one of the first comprehensive tests of the question. They present genomic, transcriptomic, histological and functional evidence that the Greenland shark retains an intact visual system well-adapted to dim conditions. The retinal tissue in the specimens they examined showed no signs of degeneration across the age range. The molecular machinery for processing low light was present and active. The authors identified DNA repair pathways in the retina that they argue help preserve photoreceptor function across centuries.

The starting point for the work was, on Skowronska-Krawczyk’s account, a video clip. She watched footage of a Greenland shark moving its eyeball to track a light source. Her observation was a biologist’s one: evolution does not tend to maintain a complex sensory organ that confers no benefit. If the eye works enough to track light, something is being seen.

The shark is not blind. The parasite is real, often present, and clearly does some local damage to the cornea. The animal sees through it, or around it, or in spite of it, well enough that the visual system has been actively preserved for centuries rather than allowed to decay.

This is a more interesting finding than the one it replaces.

What we tend to do with very long lives

In our reading of the popular coverage of this species over the past decade, there is a pattern worth naming.

When a creature lives much longer than we do, we tend to fill the gap between its life and ours with a story. The story tends to be either elegiac or tragic. The shark drifts through Arctic darkness, blind, ancient, witnessing nothing. The frame is usually a projection. It is what a human imagines a 400-year life would feel like, applied to an animal whose actual experience we have no way to access. The parasites on the cornea become a kind of natural metaphor for the cost of long life.

The revision matters because it removes the metaphor and replaces it with something more ordinary and more demanding. The shark is not a tragic figure carrying its blindness through the centuries. It is an organism whose biology actively preserves visual function on a timescale we do not have a clear way to think about. The interesting question is no longer what it must be like to live for 400 years blind. It is what it would take to preserve a retina that long. The Fogg paper points at part of the answer. Most of the answer is not yet known.

A small note about received wisdom

The blindness line has been repeated in roughly the same form for roughly thirty years. It became a fact about the species without anyone running the experiment that would confirm or refute it. The 1998 paper hedged carefully. The summaries did not. By the early 2020s the hedging had vanished entirely from popular accounts.

There is no scandal in this. It is how received wisdom tends to form about creatures most of us will never see, in environments most researchers cannot easily reach. Someone makes a careful claim with a qualifier. The qualifier drops. The careful claim hardens into a known thing. Eventually someone watches a video, notices an animal moving its eye, and goes back to look.

The shark is still there. It is still very old, still very slow, still tracking light at a depth where there is not very much of it. The story we have been telling about it was a third wrong, and the third that was wrong turned out to be the part we found easiest to imagine.