@kellyjay said
What do fossils tell you,
They are dated (via counting annual layers in rocks etc and also radiometric dating which could only be wrong if the known laws relevant to nuclear are simply false in which case none of our nuclear technology would work) and, from these dates and the fossils we observe, the evidence proves that there was a progression of different sets of species over MILLIONS of years that generally started only with the most primitive microbes then things like simple jellyfish etc came to exist then only much later crustaceans but still no vertebrates and then only much later the first fish and then much later the first amphibians and then later the first lizards and then only much later the first mammals and birds.
A similar progression of simpler life followed by more complex life also happened with plants (first only algae then also moss then ferns then trees and then more complex flowering plants).
Thus the fossil record extremely clearly proves two things:
1, The fossil record proves, and contrary to the claims of certain religions, that all the species did NOT come into existence at about the same time but rather came into existence at very different times with many millions of years between those points of times.
2, The fossil record proves there was a general progression starting with more primitive species to generally ever more complex species but also only over many millions of years. This is EXACTLY what you would expect if they evolved but NOT what would be explained by your religious claims.
There is at least so far no known alternative rational explination of 1 and 2 above other than those species evolved and this is despite many attempts to create such an alternative rational explination. Without being pedantic, we can say that means evolution theory is proven true.
If you are going to suggest something someone says about them is true, how do you know
We know because of the evidence.
what if they are wrong
The possibility of a mere claim being wrong is exactly why we scientists, unlike some (not all) theists trying to push their religion, look at the EVIDENCE to make sure the claim isn't wrong. We have already looked at the evidence for the claims for evolution. They are not wrong. Evolution theory is proven correct. And the reason why we believe evolution happened was never because somebody claimed it happened but rather because the evidence proves it happened. If somebody had made a claim that evolution happened but the evidence showed it didn't then we would all believe it didn't; no problem.