If you choose to believe that aliens are real... (they are man) What do the humans have/do that aliens have givin us. Heres an example (one of the most comonly used) The pyramids PS: this whole thread is sorta BS. just put what you want to believe was made by aliens.
Terrence Mckenna says magic mushrooms are aliens...which might explain why so many people have visions of them when their tripping on them ;P Sounds crazy but I believe it is closer to the truth than not... They are also responsible for crop circles. There's no way that 100% of crop circles all over the Earth are a bunch of people playing elaborate pranks on some farms in the middle of the night... That just doesn't make sense, and it's not logical to actually believe that.
Yeah apparently they have been found at all levels of the atmosphere on the Earth, mushroom spores... Terence Mckenna is a fascinating man. He contributed a lot to the psychadelic movement..."LSD has been known to cause insanity in those who don't take it"(lol) He's got some great google videos... edit* I just found a page here where a bunch of them are linked http://www.hipforums.com/forums/showthread.php?t=214710