Agreed... Lots of phenomenon out there that indicated we were not the first to "know" things that most of us don't know today. Stonehenge, for another example.
We have a tendency to underestimate the technology or the scientific understanding held by ancient peoples.
Perhaps this reinforces my contention that the greatest crimes ever perpetuated on humanity were the various successive burnings of the library at Alexandria. I think it would amaze us today to find out what things the people of those days already knew.
I would contend that there were ancient peoples that lived for many years just the merest fraction away from discoveries that would have started technological innovations centuries before they were realized. I happen to think that much of this collected knowledge was at Alexandria, and the loss of it was a setback on the order of thousands of years of re-discovery of things already known.