The Sumerians said the nephilim were those who "came down" to Earth and taught mankind the sciences.  Seems to dovetail pretty nicely with the biblical fallen angels account as well as the Book of Enoch.

Its an interesting topic, but I think that to validate this claim, one must first prove that angels exist from the religious perspective. There is no question in my mind that life exists elsewhere - but this life most certainly does not believe or think as we do in terms of religious followings, systems, or beliefs. To stake this claim means that the aliens know God , who may also be an alien. It is therefore a dangerous presumption, one lacking any real credibility other than speculation, fear, and uncertainty.