"In the future, their [humans] lifespan will be no more than 120 years." (Genesis 6:3b) As Adam and Eve have more children, those children have more children, and on and on it goes.
When you look at Genesis 5 you find a series of repetitive statements, each one sharing the lifespan of a father and the point in his life where there was the birth of a son. Here are some examples:
- Adam at 130 years old became the father of Seth. Adam lived a total of 930 years.
- Seth at 105 years old became the father of Enosh. Seth lived a total of 912 years.
- Enosh at 90 years old became the father of Kenan. Enosh lived a total of 905 years.
- Kenan at 70 years old became the father of Mahalalel. Kenan lived a total of 910 years.
- Mahalalel at 65 years old became the father of Jared. Mahalalel lived a total of 895 years.
- Jared at 162 years old became the father of Enoch. Jared lived a total of 962 years.
- Enoch at 65 years old became the father of Methuselah. Enoch lived a total of 365 years.
- Methuselah at 187 years old became the father of Lamech. Methuselah lived a total of 969 years.
- Lamech at 182 years old became the father of Noah. Lamech lived a total of 777 years.
If we couple together the amount of years each father lived before the birth of his particular son, then that will give us the years it took for all this to happen. There is lots of overlapping of fathers, grandfathers, and great grandfathers, etc., but if they weren't dead when the flood came, they were certainly dead after. It is 1,056 years before Noah is born and he lived 500 years before he was commissioned by God to build the ark. The worldwide flood came when he was 600 years old, which would be 1,656 years from the time Adam and Eve were sent out of the Garden of Eden.
These lifespans are striking in regards to our first quote by God about lifespan being "no more than 120 years." What could have caused God to shorten the lifespan from what was an average of 907 years (excluding Enoch in the calculation)? The answer is not hard to find. "The extent of human wickedness on the earth…[and the fact that]..everything they thought about or imagined was consistently and totally evil" (Genesis 6:5) is the reason for the decrease in lifespan. God got fed up with the way man lived in his sin nature. It made Him sorrowful and so He decided to start again with just eight seeds of human life in a boat and lots of seeds of animal life.It seems that the principle here is that man does not evolve to become better and better but actually devolves over time. So, in order to slow the process of devolving God shortened the timespan of life. It is important to face the truth of devolvement, not believe in the false assumptions of continued betterment. It will help us share the story of salvation when we do believe man is not going to get better unless God's Son enters the picture.