Okay. Look at it like this. Imagine that some genius electronics engineer developed a time viewer, where he could look back 100,000 years. And he started showing people, over his time viewer, what it looked like when dinosaurs walked the earth. Do we believe what he is showing us? How can we tell, and when can we tell, that he might have something that is reliable?
Here's when. It's only when his time viewer can trace the history from 1 minute ago, and then 10 minutes ago, and then an hour, and then a day, week, month, year, etc., showing all the things that are happening right now, in our life time, where we can trace it back to the dinosaurs, viewing everything in between if we so desire. Only THEN might we start to believe that he has TRULY developed a time viewer that can show us the past, and that the past is as many years old as scientists have suggested.
The point is, ancient pottery, and old geological features, only suggest things. They aren't a time viewer that is clear enough to make any certain estimates of time and the timeline. There are too many variables that we don't know about, that just might play a much larger role in our understanding of how old things really are.
It is GOOD that scientists make their educated guesses; it helps them to have a point to work from. But also, let them say it exactly the way it is, that they just don't know scientifically what was going on beyond about 5,000 years ago, and that their educated guesses,
ARE ONLY EDUCATED GUESSES. They really don't know.