Our Better Nature: Shark Eyeballs Are Sharp Eyeballs

In the 2002 film Minority Report, the government tracks people in real time through iris scans, and there’s no hiding from their ubiquitous scanners. When police chief John Anderton, played by Tom Cruise, is wrongly accused of plotting a murder, he buys an illicit eye transplant and becomes (according to his iris scan) a Mr. Yakamoto, who may have had his own troubles with the law.

Anderton would have entirely bested the government’s spyware with eyeballs from a Greenland shark, though. Not only would he have been 100 percent anonymous, but he also might have had perfect vision into old age. Because according to a January 5, 2026, article in the journal Nature, Greenland sharks have the best eyes in the animal kingdom.

Because Greenland sharks live where it’s hard to observe them, they are one of the more poorly studied animals. What we do know about them, however, is just as cool as the waters they ply. First, these guys are funny-looking, having been described as looking “more like a worn sock than a fearsome predator,” and seeming “already dead.” To be fair, “fearsome predator” is not in their job description. While they are said to prey in an opportunistic way on sleeping seals from time to time, for the most part they are docile scavengers.

They’re also enormous, weighing more than 2,200 pounds and reaching lengths in excess of 20 feet. Not surprisingly, as large, cold-water beasts, they’re slow at just about everything they do, right down to their heart rate of once every twelve minutes. Females reach sexual maturity at around 150 years old, and their pregnancies last from eight to eighteen years. I sure hope morning sickness isn’t a thing with this species.

There’s a real mystery afoot, or rather afin, here, as this shark lives in near-darkness in frigid waters as deep as 1.4 miles below the surface, where there’s not much to look at. In fact, Greenland sharks, which are at home in many places far from Greenland, even in deep Caribbean waters, were long assumed to be blind. In most cases, where an organ is no longer used, it either disappears or becomes vestigial, a non-functional remnant. This is thanks to natural selection, which tends to cut energy for stuff we don’t need, like growing tails, and saves it for good causes such as bigger brains.

The enigma goes deeper yet, given that Greenland sharks live a good 400 to possibly 500 years. And yet without any apparent need for eyes, not only have their peepers not shriveled up and gone away as is the case with Mexican blind cave fish and deep-sea blind lobsters, they exhibit no sign of deterioration after hundreds of years.

The presence of perfect sight in the ancient eyes of Greenland sharks seems all the more unlikely due to the fact many of these sharks are beset with eye parasites: pink, dangly, worm-like copepods that glom onto a shark’s cornea, obscuring their vision. My eyeballs itch just thinking about it.

But still, the shark eyes themselves remain free from the kinds of vision pathologies that people and other animals are known to get, such as macular degeneration and glaucoma. The authors of this recently published study say that they identified a DNA repair mechanism in the sharks’ eyes that fixes mutations — errors in copying genetic material — that happen when cells divide. In most animals, the rate at which mutations happen picks up as they age. The sharks’ fix-it process may be related to the fact that cancers, which result from mutations, do not occur in Greenland sharks.

In addition to repairing mutations in their eyeballs (and maybe in other tissues as well), Greenland sharks have another adaptation to protect their vision through the centuries. Namely, a retina packed with grease. Technically the “grease” is a long-chain polyunsaturated fatty acid called DHA, found in other animal retinas as well, but it’s much more concentrated in Greenland sharks.

While there are hundreds of people who have reached the age of 110 and beyond, none made it with their joints, hearing, eyesight, and brain function fully intact. The oldest documented person was a French woman named Jeanne Calment, who passed away in 1997 at the age of 122 years and 164 days. From what I can tell from her biography, her mind was strong right to the end. Unfortunately, though, she spent a decade in near-blindness, with the last five years totally blind (she explained in one interview that she had to quit smoking at age 117 because she couldn’t see the match to light her cigarette).

The study authors are confident that further research on Greenland sharks is likely to translate into therapies to help us not only live longer, but also keep our eyesight sharp and bodies working as designed for as long as we live. That way, no one will have to quit smoking at age 117. I’m sure there will be even more significant advantages, as well.