Answer: Adam was 930 years old when he died (Genesis 5:5), and his children and grandchildren shared similarly long life spans. Not counting Enoch, the ten patriarchs who were born before the Great Flood of Noah’s time lived an average of 900 years. Adam’s son Seth lived to be 912 years (Genesis 5:9). Lamech, Noah’s father, died the youngest at age 777 (Genesis 5:31); and Methuselah, Noah’s grandfather, lived the longest. He died at age 969 (Genesis 5:27). If Adam had lived a mere century longer, he would have been alive for the birth of Noah.

After the flood, the average human life span began to shrink drastically. The post-flood patriarchs from Noah’s son Shem (who died at 600) to Peleg (who died at 239) lived an average of 435 years. By Abraham’s time, humans were living less than 200 years. In the days of Moses, who was considered very old when he died at 120, the average person lived only to age 70 or 80: “The years of our life are seventy, or even by reason of strength eighty” (Psalm 90:10, ESV).

Why did Adam and the generations before the flood live so long?

Adam and Eve were created without sin. In this state of perfection, they were meant to live forever in paradise on earth. After the fall of man and the introduction of sin, death began to exert its destructive influence on all humankind (Romans 5:12). But with the degeneration process just in the beginning stages, there would be less illness and fewer genetic defects affecting the young race. It would have taken time for corruption and diseases to spread and increase throughout the earth. These factors alone could account for the prolonged antediluvian life spans.

While the Bible does not say, it makes sense that longevity at the outset of the race would allow humans the opportunity to accumulate knowledge and make other cultural advancements. At the same time, God had commanded Adam and Eve to “be fruitful and multiply and fill the earth” (Genesis 1:28, ESV). Longevity seems to have been God’s way of kick-starting the growth of civilization, as it would have taken centuries of procreation to fill the earth with people living mere decades.

As sin continued to work through the generations, the accumulating effects of disease and death would likely have contributed to the shortening of the human life span. Concurrently, the fall of man and the resulting curse would have produced progressively worsening influences on the earth and every creature in it (Genesis 3:17–19).

Some scholars have suggested that dietary modifications and climate changes contributed to the rapid reduction in human years after the flood. One theory, based in Genesis 1:6–7, submits that before the flood there was no rain. Instead, the earth was covered by a water canopy that created greenhouse-type conditions and sheltered people from the harmful rays of the sun. A daily mist or vapor spread over the ground to water it. By limiting radiation in the atmosphere, this canopy would have slowed the process of aging and disease. After the catastrophic flood, which emptied the water canopy (Genesis 7:11), life on earth was less protected, and the degenerative process accelerated. While a reasonable theory, there is no concrete biblical evidence to support it.

Apart from the Bible, one historical document supports the idea that most people before the flood lived to be as old as or even older than Adam when he died. The Sumerian King List is a non-biblical text from southern Mesopotamia that lists the Sumerian kings and the length of their reigns before and after a great flood. Similar to the long life spans of the pre-flood patriarchs, the most ancient of the kings enjoyed extraordinarily long reigns.