Can't they make different studies to determine age?
We know that some turtles, sharks and whales can live way more than a century if not multiple centuries, but we don't know that because we have been following them from centuries.
There's a tortoise living on the Seychelle's governor garden since 1882 and has outlived every single governor yet.
We have a picture of it dating 1886: https://upload.wikimedia.org/wikipedia/commons/f/f0/Jonathan...