fom: http://www.thebricktestament.com
When people began being numerous on earth, and daughters had been born to them, the sons of God, looking at the women, saw how beautiful they were...
...and married as many of them as they chose. In those days, and even afterward, giants lived on the earth, for whenever the sons of God had intercourse with human women, they gave birth to children who became the heroes mentioned in legends of old.