Some earlier versions of mankind had great knowledge too and not all of that has been preserved for us. Try to rebuild the Pyramids of Gizeh today for example. Do we today know exactly how this stuff worked?
It's pretty easy for us to rebuild the pyramids today, but what's hard is trying to do so with the same level of technology the Egyptians probably had at the time, which makes them wonders of the world instead of just another easy-to-make mudhut.
