I would say that this is against both evolution and creationism.  \n\nIf humans were not from earth then why would we have so many similar internal organs to other animals?  I mean I doubt any extraterrestrial creature could have a pig's heart transplanted into their body like humans can.\n\nIt could be that humans were in some way altered by aliens or our culture is influenced by aliens.  But this lacks any real evidence at present and is thus a very unlikly (but not impossible) case.\n\nPersonally I think there are aliens of some sort but they are not amongst us in any conventional sense at the moment.