Randy angels

1. Gen 6:1-4 is enigmatic, in part because it's so compressed, and in part because it uses a designation ("sons of God") that has no parallel elsewhere in the Pentateuch.

A popular interpretation is that it describes fallen angels mating with women, thereby spawning a race of hybrids. 

2. There are problems with that interpretation. For one thing, even if the "sons of God" are angels, they are never identified as fallen angels. The passage contains no background information concerning a primordial angelic fall. So on the angelic interpretation, there's no narrative assumption that angels mating with women was illicit. That requires a backstory regarding rebellious angels. But that context is missing. 

3. Scholars fall into two basic camps. Some scholars think the text is mythological. They have no problem with mythological interpretations of Scripture because they think Scripture frequently reflects a mythological outlook. They don't think this incident ever happened–or could happen.

4. Moreover, the interpretation offered by critical scholarship isn't angelic but polytheistic. They think the text describes gods siring demigods by mating with women. 

5. Yet other Christians think the angelic interpretation is realistic. But in that event, the angelic identification is equivocal. In order for angels to sire offspring by mating with women, the angels would have to transform into men, with male sexual anatomy and seminal fluid. At least temporally, the angels would cease to be angels, becoming human males at an anatomical, genetic, and chromosomal level. 

But even assuming that angels have that ability, the offspring wouldn't be hybrids or half-breeds but purebred humans. So that fails to explain what made the Nephilim superior to normal human males.