We've all been told that fossils are dated by the layer of rock that they are in, and the layer of rock is dated by the fossils that they contain. I've always f

We've all been told that fossils are dated by the layer of rock that they are in, and the layer of rock is dated by the fossils that they contain. I've always found that hard to believe. AIUI prehistoric dates are corroborated by radioisotopic dating, similarly to using C14 for much more recent dates.