Dust McAlan said:
When recalling this, that the Pharoahs called themselves sons of God, and that the Bible clearly references the "sons of God [that] came in unto the daughters of men" it's difficult to pass off the notion that the nephilim were extraterrestrial.
Given that the Old Testament is based on Jewish sources, it seems unlikely that the "sons of God" would be Pharaohs, doesn't it? My understanding has always been that the "sons of God" were those loyal to the Creator while the "daughters of men" were "heathen" women or whatever you want to call them, that interbreeding being why it caused such an uproar. I don't recall the verses, but I remember my Scofield study Bible pointed out that angels, as Pale Horse implied, do not have gender. I imagine that makes pollinating a little difficult, even for a preternatural being.
Meanwhile, some Christian named Chuck Missler thinks the nephilim were naughty little gray men who came to pollute the world against God's will. Seems a bit odd to me that God would create an alien species just so they could screw with us, but there are weirder passages in the Bible.