Some maintain that these verses assert that angels married women before the Flood and engendered a race of giants. This idea sounds like the sub-plot of a science fiction story! But can it be the truth?
It is true that verse 2 states that the "sons of God. . . took wives for themselves of all whom they chose." These "sons of God," however, were not angels. The fact is that angels do not marry. Jesustells us this clearly: "For in the resurrection they [humans] neither marry nor are given in marriage, but are like angels of God in heaven" (Matthew 22:30; see Mark 12:25).
Angels cannot cohabit nor reproduce with women. Angels are spirit beings (Hebrews 1:13-14). Women are human beings. Angels and women, then, are two different kinds of being. Kind reproduces after kind, and different species cannot breed.
In his modern, perverted science—"falsely called knowledge" (I Timothy 6:20)—Satan encourages men to experiment with the crossing and mixing of the most unlikely creatures. For example, goats have been genetically altered by the insertion of a spider gene to produce silk products that God never intended in His original design. Right from the beginning, at the re-creation of the world(Psalm 104:30), God says that this is not to be. He establishes a strict law that each kind must reproduce only after its own kind (Genesis 1:11-12, 21, 24-25).
This rule is also backed up and made clear by the context of our difficult scripture. In Genesis 6:3, God says, "My Spirit shall not strive with man forever, for he is indeed flesh." He is speaking of fleshly mankind here, not angels. Although it is true that the children of these couples were "mighty," like their parents, they were still only human.
A third meaning refers to mankind in general, because all men are sons of God by creation: "I said, 'You are gods, and all of you are children of the Most High. But you shall die like men . . .'" (Psalm 82:6-7). Although the King James and New King James versions have "children of the Most High," many other translations have "sons of the Most High." Additional verses use similar terminology to refer to humans (Malachi 2:10; Luke 3:38).
Through Adam, then, every human being is a child of God.
Since these "sons of God"—those who are the subjects of our difficult scripture—were obviously not regenerated Christians, and could not have been angels, it is evident that they were simply human members of mankind in general: Men who had forsaken God and were intermarrying in defiance of His law.
We should note one final point. Genesis 6:4 reads, "There were giants on the earth in those days, and also afterward, when the sons of God came in to the daughters of men and they bore children to them. Those were the mighty men who were of old, men of renown."
This verse shows that giants and extraordinarily mighty men existed after the sons of God married the daughters of men and implies that they existed beforehand as well. It does not state that such huge and powerful men were the result only of these marriages. Giants have existed throughout recorded history, before and after the Flood and down to modern times.