Originally posted by WrittenFromUtopia
It's really clear in context of Genesis 4-6 that the 'sons of God' were the believers in God and their descendants and families after them. They were in covenant with God. When they married daughters of men, or the ungodly (those not in covenant with God), they sinned and polluted God's gracious covenant community. Thus, the flood, as Noah was seen to be the last of God's elect left on the earth at this time as a result of so much covenant breaking and inter-marriage with the pagans.