I was having a conversation with a friend last night, and he mentioned that he believes that aliens have come to Earth to ancient societies, helping them take actions beyond the the technological capabilities of those societies. Examples that my friend gave me were Stonehenge and pyramids. I'm pretty sure that the pyramids were within the technological capabilities of the builders, but it's never too late to be wrong! As for Stonehenge, I just plain don't know enough about it to draw much of an opinion. Still, there are probably a handful of very plausible explanations that make believing in alien help a little silly. What do you all think? I know there is a thread on whether or not aliens have ever visited Earth, but after talking to my friend I'm interested in getting more specific. I contend that aliens have not come to Earth in order to help ancient civilizations undergo actions beyond what they were capable of, but I don't have the knowledge base to explain why with particularly compelling information.