There are two prevailing views concerning the meaning of the first part of Genesis 6 concerning the union between the “sons of God and the daughters of men.”
1. The first interpretation maintains that during those days humankind was able to partake in some sort of mysterious reproductive union with angels; the result of this union being a superhuman race. The problems associated with this interpretation are many, so I will only address the most significant ones.
First of all, this type of reproductive intercourse between spirit and matter is not supported by the witness of Scripture as a whole. Genesis 6 is the only place in all of scripture where this idea could be read into the text. The rule of interpretation is: One does not build a doctrine or theology upon an isolated interpretation of one text -- especially if the interpretive idea is not supported any where else in scripture. The fact that this type of reproductive intercourse is not supported by scripture by the witness of scripture as a whole creates a serious problem in one’s attempt to validate this interpretation.
Secondly, this interpretation does not line up with the historical experience of the Judeo-Christian tradition. While there is record of spiritual sexual transgressions made by incubi and secubi spirits (sexual demons), there is no record in either historical or contemporary experience where this type of spiritual sexual transgression resulted in the material conception of a new being.
Thirdly, the text of Genesis 6 states that God was sorry that he had made humankind because of his wickedness resulting from this union between the “sons of God” and the “daughters of men.” If the “sons of men” were angels, and it was their sin of pursuing the “daughters of men” which created all this wickedness, why would God feel sorry that he had made humankind, instead of feeling sorry that he had made angels?
2. The second interpretations maintains that the “sons of God” were those men who were among God’s chosen covenant people (i.e. the Israelites), and that the “daughters of men” were those women of other nations who were not counted among God’s chosen people -- i.e. who followed the ways of paganism (or “men”) rather than the ways of God. The wickedness that resulted from this union came into being because the pagan women drew the men away from their covenantal relationship with God. Therefore, Genesis 6 records the first instance of God’s people becoming “unequally yoked” with unbelievers. This interpretation is in line with the entirety of the Biblical witness, the historical Judeo-Christian tradition, and contemporary Christian experience. The fact that the offspring of these unions became “mighty men” is more likely the result of a new genetic mixture, rather than the result of a reproductive union between two different species within creation. Just as a dog cannot reproduce with a cat, a human cannot reproduce with an angel.