The flat earth theory (taught as fact) was based on scientific observations of the time. They were dead wrong, but it was the "science" of the time.
I wonder what theories will be the norm 200 years from now?
whatever theories there are in 100 years, almost certianly they will be expansions of what is currently understood. Like Newton wasn't "wrong", yet Einstein eclipsed Newton's work, evolution will undoubtedly stand. Yet I'm sure that more details will expand it.