A Greenland shark photographed near the seabeddotted zebra/AlamyA genomic study may have revealed how Greenland sharks live for centuries and yet rarely get cancer.These sharks (Somniosus microcephalus) are slow-moving dwellers of the deep that can reach more than 6 metres long and weigh over a tonne. We know little about their lives because they roam in dark, cold waters, but it is thought they dont reach sexual maturity until they are 150 years old and their lifespan has been estimated at about 400 years, making them the longest-living vertebrates that we know of.