None of the explanations offered in the accompanying article imply that God randomly selected the life span of early humans or that He simply reacted to natural disasters in shortening human life. Rather, Genesis 6:3 states that God acted purposefully to shorten human life spans, and Genesis 6:5 and 11 imply that the shortening of human life spans at the time of the Flood served a specific spiritual purpose.
Why did God allow for long life spans in the first place? Long life expectancies early in humanity’s history reflect God’s mercy and provision. Long life spans make it possible for human technology and civilization to emerge rapidly. Living 900 years gives people ample opportunity to make discoveries, develop technology, refine technological achievements, and teach all that has been learned to ensuing generations. Under these conditions, human civilization can make dramatic advances in relatively few generations.
One benefit of a shorter human life span is that it serves to limit the spread of wickedness. An exceptionally evil person can hurt, destroy, or limit the effectiveness of a large number of righteous people during the course of 900 years. Moreover, wicked people find it easier and safer to wreak destruction upon the righteous than they do upon other wicked people. The net result of such long life spans is that the righteous tend to be exterminated whereas the wicked tend to survive. Over time, the balance of the population tilts toward the wicked, with only a few righteous people left. By truncating human life spans to only about 120 years, God mercifully limited the spread of evil, ensuring righteousness a presence in society after the Flood.
As indicated in the Telomere Loss portion of the accompanying article, the amount of telomerase activity within a cell can shorten or lengthen the life of that cell. Limited telomerase activity within cells shortens the life span of cancer cells as well as normal cells. If telomerase levels were higher, cancer would quickly rise to become the number one cause of death in humans. By limiting the growth of cancer, and minimizing human suffering, God again showed His mercy toward the human race.
The long life spans during the days before the Genesis Flood provide people today with a helpful object lesson. Many seem to think that “life’s too short,” that life would be better if people could just live a few more years. The human condition in the days just before the Flood suggests the opposite. It serves as a reminder that people are much better off with brief life spans. God allows people to live on Earth long enough to recognize and choose (or reject) Him, long enough to fulfill their destiny, and long enough to receive the training they will need for the new creation. Once that work and training are accomplished, however, Christians can move on to a life far more wonderful and blessed than anything possible on Earth (see 1 Corinthians 2:9). Therefore, believers can rejoice that God has shortened humanity’s race toward the heavenly prize.