It is well known that the age of trees can be determined by the annual rings. The animal world is structured differently, so scientists have to resort to completely different methods for assessing age.
In a recent study of the largest fish in the world, the whale shark, scientists from the Australian Institute of Marine Sciences led by Mark Mikan resorted to measuring the level of the carbon-14 isotope in the bone tissue of its vertebrae to determine the age.
Carbon-14 is a radioactive element naturally present in the Earth's atmosphere, it is absorbed by all living things. However, its level has doubled after numerous nuclear tests carried out by nuclear powers during the Cold War in the last century. This automatically increased the concentration of carbon-14 in the organisms of living things.
The object of the researchers' study was the vertebrae of whale sharks, which have visible stripes (analogs of annual rings on trees), the number of which increases with the aging of the fish. According to some scientists, each new band is formed within a year, while others insist on a six-month cycle.
Everything fell into place after carbon-14 measurements were taken in the annual streaks of two dead whale sharks. It unambiguously showed that the next strip is formed annually. The findings helped establish the lifespan of whale sharks. It turned out that they live for 50, not 100 years, as previously thought.