How much of the element has been added / taken away over the years? Recent evidence has shown radiometric dating to be potentially flawed, due to the ample presence of helium isotopes in certain crystals which were thought to be millions of years old, but in fact cannot be more than 14,000 years old because if they were any older the helium would have dissipated. More on radiometric dating can be found here: https://All this to say, even the most solid scientific methods for determining the age of organic and inorganic matter have been proven to work up to 40,000 years.
Naturalistic evolution looks to the fossil record as its authority.
A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age.
This problem is now reduced by the careful collection of samples, rigorous crosschecking and the use of newer techniques that can date minute samples.
Related Truth: Is punctuated equilibrium compatible with the Bible?
Love-hungry teenagers and archaeologists agree: dating is hard.