Giants and angel-human crossbreeds?

If you’ve seen the recent movie Noah starring Russell Crowe, you might have been confused by the giant rock monsters. While there was a lot about those characters that was made up for the movie, they weren’t entire without a basis in Scripture:

When man began to multiply on the face of the land and daughters were born to them, the sons of God saw that the daughters of man were attractive. And they took as their wives any they chose. Then the Lord said, “My Spirit shall not abide in man forever, for he is flesh: his days shall be 120 years.” The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of man and they bore children to them. These were the mighty men who were of old, the men of renown. (Genesis 6.1-4)

If you’re wondering what’s going on here, join the club. Who are the “sons of God” and who are the “daughters of men”? Are the “sons of God” angels, making their children angel-human crossbreeds? Or are they descendants of the righteous son of Adam and Eve, Seth?

The word Nephilim means “giants” – who are they? Are they the children of the “sons of God” and the “daughter of men,” or something else? And who are the “mighty men…of old, the men of renown”? Are they the people who inspired ancient myths found in other cultures (e.g. ancient Greek myths)?