Great white sharks are longer in the tooth than we thought. Traditionally, researchers age a great white (Carcharodon carcharias) by tallying the alternating light and dark bands that form on the animal’s vertebrae as it grows, similar to rings on a tree. Using this method, experts believed the species had a life expectancy of about 30 years. But now, scientists have harnessed radioactive remnants of the Cold War to conduct the most precise age measurements of great whites ever—and their results blow the previous estimate out of the water. Hundreds of nuclear bomb detonations in the atmosphere prior to a 1963 test ban treaty doubled the amount of radioactive carbon found in the ocean. Great white sharks absorbed this radiocarbon into their continuously growing skeletons. As the radiocarbon in the ocean dissipated, so did the amount taken in by the sharks. After measuring the amount of radioactive carbon in a great white’s vertebrae, the researchers calculated the age of the shark. The oldest great white aged by the researchers lived a staggering 73 years, the team reports today in PLOS ONE. Comparing the amount of radiocarbon in each band on the shark’s vertebrae, the team discovered that visible bands only annually form until a shark reaches its 30s, when the bands become too thin to individually distinguish. The new life expectancies—40 years for females and 73 years for males—suggest great whites reach sexual maturity later than previously thought, making young deaths more devastating to the species. The team hopes the new information helps conservationists working to save the great white shark from the jaws of extinction predict how the species’ population will change over time.