According to experts, Greenland sharks are now the longest-living animals on the planet.

Radiocarbon dating of eye proteins was used to calculate the ages of 28 Greenland sharks, and one female was believed to be 400 years old. A bowhead whale believed to be 211 years old held the previous vertebrate record.

“We had our expectations that we were dealing with a unique species,” said lead author Julius Nielsen, a marine scientist at the University of Copenhagen, “but I believe everyone performing this research was really startled to hear the sharks were as ancient as they were.”

Greenland sharks are enormous, reaching lengths of up to 5m. Despite this, they only grow 1cm every year. They may be observed swimming slowly in the North Atlantic’s chilly, deep waters.

A newly tagged Greenland shark returns to the deep and cold waters of the Uummannaq Fjord in western Greenland. Image credit: Julius Nielsen

The team believes the animals attain sexual maturity around 4m in length. And, based on this new, extremely long age-range, it appears that this does not occur until the animals are around 150 years old.

The discovery was made feasible in part by atmospheric thermonuclear weapons testing in the 1960s, which generated large amounts of radiocarbon, which were then absorbed by species in ocean ecosystems. Sharks with high radiocarbon levels in the nucleus of their eye tissue were thus born after the so-called “bomb pulse,” and were less than 50 years old, whereas sharks with lower radiocarbon levels were born before that, and were at least 50 years old or older, according to the research authors.

The scientists then computed an age range for the older sharks based on their size as well as previous data on Greenland shark birth size and fish growth rates.

The sharks were at least 272 years old, and may be as much as 512 years old (!) according to the results of the investigation, with 390 years being the most likely average life span, according to Nielsen.