These verses describe a special period in human history. The number of people had become much larger. The choice of someone to marry was no longer so limited.

Who are the sons of God? The most plausible explanation is that these are the strongest and most powerful men of humanity at that time. It may seem strange to put it this way. It is important to note that the words of God in Hebrew can have the meaning of a superlative (e.g., Genesis 30:8; 1 Samuel 14:15; Jonah 3:3). In Genesis 30:8 (see ESV footnote) it literally speaks of wrestlings of God. In 1 Samuel 14:15 we read about a panic from God (see ESV footnote). This means that there was a very great terror. In Jonah 3:3 we read that Nineveh was an exceedingly great city or (see ESV footnote): “a great city of God.”

We can translate sons of God in our text with the strongest sons. When the strongest among men looked around this earth, they saw very beautiful young women. These young women were very beautiful, but they were daughters of human beings. That means they did not have the physical strength to resist the strongest among men. Sinful living according to one’s own desires had taken such a big place on the earth that the strongest men took for themselves such women as they wanted. Among the strongest and most powerful men it was becoming more common to take a number of women for themselves. According to the law of the strongest, the most powerful took the beautiful women they wanted. This was a sign of the increasing apostasy of men on earth.

The Lord responds to this in Genesis 6:3. The people at that time became very old. But it is the Spirit of God that gives life. No one can live without the breath that the Spirit gives, and no one can continue to exist without it. The Lord saw that people were abusing their lives more and more. He would show that people depend on his Spirit for their lives. The Hebrew word “olam” translated in Genesis 6:3 as always or forever can also indicate a very long period of time. God’s punishment for mankind was that they would no longer live for such long times. The ages that were around 900 then would become much shorter. In this way, man would realize that he is flesh; that he is a mortal man. He would experience that he is mortal and that life is fragile (see also Psalm 103:14–16). The age of man would decrease more and more, and a time would come when people will not get older than around 120 years.

At the time the Lord said these things, there were also giants on earth. We should think of giants as people who, by their strength and height, stood out far above the others. After the flood we also read about giants (see e.g., Numbers 13:33). So there were giants on the earth at the time when the strongest men appropriated the most beautiful women for themselves. This raises the assumption that from the union of the strongest men and the most beautiful women giants were born. The food menu may also have played a role in this. With the most powerful people there was a lot to eat, which also ensures greater growth. It is also known from the Middle Ages that people from the upper levels of the population became stronger and taller than the rest of the population, mainly through nutrition. When you think about this and consider that the strongest men had relationships with the most beautiful women, you can imagine that from this came the most striking men—men who clearly stood out above the weaker portion of the rest of the people. They are therefore called the mighty men of prehistory. These are the men who made a name for themselves as the strongest and most powerful in the time before the flood.