If the Classical civilization created by our race had never fallen, and the libraries and philosophical schools had not been destroyed by the Christians, we might have discovered America in 492 instead of 1492, set foot on the Moon in 969 instead of 1969, and had a thousand other advances we can't even imagine now.
Discussion
There actually is a serious theory that approximately 1000 years were added incorrectly. (In my opinion to distance us from the classical Roman civilization that was hated so much, but I digress.)
I read the first book of "History: fiction or science" by Anatoly Fomenko. He has a purely mathematical approach, proving that many historical writings from different epochs are really describing one and the same thing. And are thus of a similar age.
I personally couldn't point out any issues with his approach and believe he's right.
Can really recommend the book if interested.