1500 years or so had passed since God made Adam and Eve and the human race had spread all over the world. God had told people to be fruitful and certainly by this time with people living 7/800 years and having many many children, the population of the earth had grown considerably. Some estimates say that this could have been in the region of 30,000 million people – ie 30 billion and the current population in 2016 is in the region of 7 billion but we are not given any clear information on this, only that the number had increased.
Verses 2 & 4 speak of Heavenly beings (or Sons of God) taking the beautiful young women and having children by them who were giants and heroes of the day – they were known as the Nephilim.
Now there are several interpretations on this part of the story. Jewish literature speaks of these being Angels who strayed from their original order and came down to earth and “married” human women. Jude v 6-7 speaks of the Angels who left their positions of authority and are now being held in darkness awaiting judgement. We know too from Job 1 v 6 that the angels were called before God to report on what they had been doing.
The name “Nephilim” comes from the Hebrew word for “fallen ones” and were known to be people of great size and strength and viewed as the heroes of old but in Gods eyes they were sinners.
Others say that this cannot be possible due to God’s order of creation and in Mark 12 v 25 Jesus says;
For when the dead rise to life, they will be like the angels in heaven and will not marry
This implies therefore that it is not possible for there to be intermarriage between angels and humans although many ancient mythologies mention this.
“Sons of God” more usually refers to human beings (Isaiah 43 v 6, Hosea 1 v 10, Luke 3 v 38, 1 John 3 v 1)
This could be a reference to Godly men marrying sinful women – the daughters of men, possibly from Cain’s line who brought their sinful ways with them.
“Sons of God” can also be a reference to Kings who were revered and worshiped in some areas and built up corrupt kingdoms for themselves.
Then the Lord said “I will not allow people to live for ever; they are mortal. From now on they will live no longer than 120 years” (v 3)
Other translations say “My Spirit will not contend (or remain) with man forever”. God is holy and cannot tolerate the evil sinful nature of man and the depths which they had reached by this time.
He then declares a life span of 120 years. Again there are two interpretations of this. The first is that he was giving notice of his plan to destroy the earth. Later on we read that Noah appears to have been around 500 years old when God reveals his plan to him but the flood did not occur until he was 600 years old. Others take the more literal approach in that God declares that man’s life will be no more than 120 years. In Psalm 90 v 10 the Psalmist refers to the length of our days being 70 years.
When the LORD saw how wicked everyone on earth was and how evil their thoughts were all the time, he was sorry that he had ever made them and put them on the earth. He was so filled with regret that he said “I will wipe out these people I have created, and also the animals and the birds, because I am sorry that I made any of them (v 5-7)
The people on earth were getting on with their lives with no thought or regard to their creator so God was full of pain and regret that they had rejected him. The animals suffered under this too although they were morally innocent, they had been placed under the authority of man who was sinful.
But the Lord was pleased with Noah (v 8)
Noah was not perfect, we know that he made mistakes but the accounts imply that he was the only one left who still tried to follow and honour God and in comparison to his contemporaries he was a Godly man.
All quotes from The Good News Bible