You're using the god argument, Sprout. Others cannot explain every single instance in detail, therefore it must be god/aliens/ancient civilizations/lizardmen.
Fascinating crop circles and math you say? Humans could understand it, therefore humans could've created it, it's just that simple. Why do you assume idiots created the crop circles in the first place?
Like others, I'm not really questioning intelligent life on other planets, it's quite likely there is something out there. The story about them leaving some patterns in crops is silly though and a critical mind would never accept it. It's nice to trip out on some science fiction stories but they rarely have anything to do with reality.