The way they do the dating of how old the fossils are is by way of circular reasoning.

Ask the paleontologist, sir, how do you know the fossils are 72 million years old, and he'll tell you the fossils are 72 millions years old because of the rock in which they were found. Since we know the rock is that old, therefore the fossils are that old too.

Then go ask the geologist, sir, how do you know the rocks are 72 million years old, and he'll tell you that we know the rocks are 72 million years old because fossils were found in it, and they are 72 million years old.

The more astute believer in evolution will point to radioactive dating. We know that so-and-so material has a such-and-such radioactive half-life (the time it takes for the radioactive material to decay/break down so that only half of the original amount remains), and we know what the materials are that the substance breaks/decays down into. So, we measure the amount of material it breaks down into, along with the radioactive material still there, and by these compute how long it has been radioactively decaying. Ergo: it is so-and-so many years old.

Sounds good, except ... it is arrogantly unscientific due to an overwhelmingly major flaw.

What is that deal-breaker flaw? The entirely unscientific assumption of how much radioactive material there was originally present! How do they know? They weren't there so-and-so many years ago. How much was present there originally? They ... don't ... know. They assume it was ALL radioactive material to start with, without a shred of fact to substantiate that assumption.

The fact is, they want to believe in evolution because if evolution is true, then there is no need for a creator God. As one atheist said, not only do I not believe there is a God, I don't WANT there to be a God, as it would interfere with the way I want to live my life.

Thus, we see the evil of a sinful heart as the true reason they believe in evolution.