You can’t count the years on a Greenland shark. It has no hard bones to lay down rings, so in 2016 a team led by Julius Nielsen tried the one part of it that never gets renewed: the very centre of the eye lens, made when the shark was born and left alone ever since. They radiocarbon-dated it in 28 sharks. Only the three smallest carried the extra carbon that the nuclear tests of the 1950s and 60s put into every living thing, so only those three were born after the bombs. The largest came out at about 392 years, give or take more than a century. So the oldest vertebrate anyone has measured was dated by the part of it that had stayed a newborn the whole time.