According to other verses like Psalm 90:10, man has a different lifespan. But Genesis 6:3 probably uses a calendar that doubles the years from 60 to 120. The ancient Mesopotamians had only two seasons: summer and winter, and the average person would’ve easily counted them as years. The Mesopotamian year was originally shorter than 12 months, eventually evolving.
6:4 The Nephilim were on the earth in those days – and also afterward – when the sons of God went to the daughters of men and had children by them. They were the heroes of old, men of renown.
Some say this contradicts the story of the Flood which left only Noah, his wife, and his sons and their wives alive. But this is true only if the giants are some sort of supernatural beings, and not human beings. It’s only those who believe that the Nephilim weren’t human, but something like fallen angels, that would have a problem with this. As we see from Numbers, the Nephilim existed in Moses’ day and were clearly seen as human beings, not descendants of angels or anything like that.
6:6 And it repented the Lord that he had made man on the earth, and it grieved him at his heart. (KJV)
