I enjoyed that show a lot, when I watched its early seasons. What I liked the most is their questioning of unexplained things. Granted, all their answers always lead to ET intervention, but despite that, and some viewers not necessarily agreeing with their point of view, science hasn't given much answers to the discrepancies and unsolved mysteries neither. Despite all the advances in our science and technology, many aspects of our history remain unknown. All we can do is speculate and try to connect the dots with what we know. Humanity had tens of thousands of years to become what it is today, there's no doubt a lot of our ancient knowledge was lost. Whether it is/was aliens or not, nobody can hold a definitive answer.
And yes, Giorgio's hair is legendary. My reaction the first time I saw him on that show was: WTH is that on his head?
Haha aliens
The thing I wanted to get across is that we haven't exhausted all possibilities here, before we jump to an alien conclusion. Not just for history, but for alot of things.