The alien factor put to one side, I am prepared to believe that we may have reached a previous high state of technology pre-cataclysm, whether with the help of extraterrestrials, well, I can entertain the thought but it's up to how you interpret the ancient texts and the DNA anomalies. Thought provoking, for sure.
There's a few other vids on YouTube on this particular vein of "Ancient Astronaut" theory but this one is entry level and covers the bases. I found it interesting, at any rate, when I first stumbled across it.
I love this stuff!
After 12/21/12 turned out to be a dud, I had wondered what all those web sites were going to do (and how I would enjoyably waste my time looking at them)