A Greenland shark studied in 2016 was estimated to be nearly 400 years old, meaning it may have been born around the time Shakespeare’s era was ending — and, astonishingly, would not have reached sexual maturity for more than another century.

In 2016, researchers put an age to a Greenland shark that is hard to take in. The largest animal in their study was estimated at nearly 400 years old, which would place its birth around the time Shakespeare’s era was drawing to a close. Stranger still, by the same research a shark like that would not have reached sexual maturity until it was around 150, more than a century into a life most creatures never get a fraction of.

The figure is astonishing, and it also comes with a wide margin of error worth stating plainly.

How you age a shark with no birth certificate

Greenland sharks leave no growth rings to count, so the team needed another clock. They found one in the eye.

The nucleus at the centre of a shark’s eye lens forms before birth and is not replaced over its life, so the carbon locked inside it is a chemical snapshot of the moment the animal began. By radiocarbon dating that tissue, and using the spike of carbon-14 that nuclear weapons tests left in the oceans in the 1950s as a time stamp for the younger sharks, the researchers could estimate how long each had been alive. The work, led by Julius Nielsen and published in the journal Science, covered 28 female sharks, ranging from under a metre to just over five metres in length.

Nearly four centuries, give or take

The headline number needs its uncertainty attached. The largest shark, around five metres long, came out at roughly 392 years old, but the method carries a margin of about 120 years either way. The honest statement is that this animal was at least 272 years old and possibly more than 500.

Even the low end of that range is extraordinary. It makes the Greenland shark the longest-lived vertebrate known, outlasting the bowhead whale and everything else with a backbone. At the central estimate, the shark was swimming the cold North Atlantic before the first telescopes were turned on the night sky.

A childhood longer than a human lifetime

The detail that lingers is not the death but the slowness of the life.

The same research put sexual maturity at something like 150 years of age. A Greenland shark spends longer reaching adulthood than any human being has ever lived, drifting through the deep, cold dark and growing at perhaps a centimetre a year. By the time it can reproduce, generations of faster animals have come and gone many times over.

That pace is tied to the cold. These sharks live in near-freezing water, their metabolism turned right down, and a body that does everything slowly tends to do it for a very long time. It is a life lived almost in slow motion, paced to water that barely climbs above freezing from one century to the next.

Why the longevity is also a liability

There is a sting in the story. A species that takes 150 years to breed cannot replace its numbers quickly, which makes it badly exposed to anything that kills adults faster than the slow trickle of new ones can keep up.

Greenland sharks are caught as bycatch and were once hunted in large numbers for the oil in their livers, and a population that recovers on a timescale of centuries has little room to absorb that. Slow to mature and slower to rebuild, they are guarded by little except the cold and the depth that hide them. The same biology that produced a nearly four-century-old animal is what makes the species so hard to protect: by the time a shark born today is old enough to matter to the population, every person reading this will be long gone.