The marvel of Haile Gebreselassie, two time Olympic gold medalist in the 10,000 meters and former marathon world record holder, is that his true age isn't known (it's listed as 40, but many believe he's actually older, which would make some of his recent accomplishments even more impressive). The same goes for several noted baseball players from Central America, and likely millions of other people who aren't famous but come from countries less particular with birth certificates. If there's no scientific method by which to measure a human's true age, in terms of years spent on earth, how are scientists supposed to do the same for animals?

Much like Gebreselassie, little is known about the lifespans of great white sharks. The previous age-determining method was to count "growth band pairs," deposited annually, in their vertebrae, according to the Northeast Fisheries Science Center. Except this procedure was often made difficult by weakly deposited pairs nearly impossible to count; also, some questioned whether they were truly left every year.

"Ageing sharks has traditionally relied on counting growth band pairs, like tree rings, in vertebrae with the assumption that band pairs are deposited annually and are related to age," said Lisa Natanson, a co-author of the study. "In many cases, this is true for part or all of a species' life, but at some point growth rates and age are not necessarily in sync. Growth rates slow as sharks' age. Deposition rates in vertebrae can change once the sharks reach sexual maturity, resulting in band pairs that are so thin they are unreadable. Age is therefore frequently underestimated. " 

Instead, researchers of the Northern Fisheries Science Center tried bomb radiocarbon dating, based off the environmental imprint left by nuclear bombs from the 1950's and 1960's, and contained within a host of living things, including sharks.

Not only was the technique easier to use and more consistent, it also yielded ages much older than the previous band pair method and older than previous research had assumed. By the old way, none of the sharks tested higher than 23 years old. Under the new method, one male shark was estimated to be 73 years old. Another male was 44 and the oldest female was 40.

"Natanson and colleagues suggest that either white sharks are living significantly longer and growing slower in the Northwest Atlantic than either the Pacific or Indian Oceans, or longevity has been underestimated in previous studies," according to the press release. 

Haile G: