That is the biggest issue with that damn show. It lessens the amazing accomplishments of humanity. I hate that some people are more apt to jump to "aliens did it" than "man, some of these ancient societies were brilliant".
Hell, it's still happening to this day with people claiming that everything from cell phones to stealth aircraft came from tech stolen from crashed UFOs at Area 51.
It's sad that these people can't concieve of humans being capable enough to produce technology.