It's important to understand that theories are still believed by the vast majority of scientists. When something is a theory it is the best conclusion that the most qualified people in the world have come to based on the evidence we have.
Not all theories have the same degree of acceptance. In different disciplines, there are greater or lesser degrees of general acceptance.
Only during my lifetime, did they discover the settlement of norsemen in Canada, Eric the Red I believe, year 1,000.
That altered the beliefs about that topic, quite drastically. Staying with the settlement of North America, we still are not settled on dates for the first arrivals from NE Asia, but we are more certain every few years.
Trying to grapple with these topics scientifically, across disciplines, makes it ridiculous to waste time on young earth creationists, when archaeology, geology, argue so strongly against it.