In Genesis 5, a brief account of the lives of Adam's descendants is narrated. All of them had long lives, for instance, Adam lived 930 years, Seth lived 912 years, etc.

But in Genesis 6:3, God seems to shorten the lifespan of man to 120 years or at least that's what I understood reading that verse. Did I understand it right? How is this fact explained by people who consider Genesis to be literal history?


3 Answers 3


Answers in Genesis and Creation Ministries International, two young-earth creationist organizations, have similar answers to this question. They don't attribute a direct supernatural cause, but instead attribute the age drop-off primarily to genetics.

Both cite several factors:

  • Environmental changes following the flood: probably nothing more than a minor effect, since Noah lived another 350 years after stepping off the ark
  • Genetic bottleneck at the flood: the gene pool was reduced to eight people, perhaps causing the loss, via genetic drift, of genes contributing to longevity
  • Possible detrimental mutations: particularly in Shem (who died at a much younger age, 600, than his brothers)
  • Genetic bottleneck at the Tower of Babel: the gene pool was again divided, potentially having a similar effect as the bottleneck at the flood

Some of the ideas that both reject as insignificant are a change in diet (from vegetarian to omnivorous) and reduced oxygen levels after the flood.

Regarding Genesis 6:3, see this related question. AIG interprets the verse to mean that God was allowing mankind to live another 120 years before destroying it with a flood:

We can see that Genesis 6:3 does not deal with the length of time a human will live. Rather, it indicates the longsuffering nature of God in the midst of His wrath. He was allowing even the most evil people of Noah’s time 120 years to repent of their sin before he would judge them with a global flood.


  • 1
    I got defensive at first when I read this answer, I thought briefly to myself, "Hey! I do not have any detrimental mutations!" Then I quickly remembered whom I was named after...
    – ShemSeger
    Commented Sep 11, 2015 at 16:47
  • 2
    A note about Shem though: he outlived Abraham who was about 10 generations away Commented Oct 10, 2015 at 11:47
  • I would think that this answer is non-ideal given that science does not back up the idea that there hasn't been significant genetic bottlenecking of humans in the last few thousand years. That said the OP tagged this with young-earth-creation, so perhaps scientific evidence is not required for this answer
    – Kevin
    Commented Oct 19, 2020 at 17:51
  • @Kevin I'm not sure if you are saying that there is or is not scientific evidence of a human genetic bottleneck, but there actually is. While the era during which the bottleneck is believed to have occurred according to the researchers doesn't nicely match up with the most commonly accepted Biblical chronologies of Genesis, it actually is relevant because Young Earth Creationism often teaches that these scientific estimations of age are not accurate due to misunderstanding the true history of the world. Commented Jun 15 at 11:19

An alternative (or additional) answer would be that the age before the flood was counted in seasons, which would correspond with Seth being born when Adam was around 33 and Enosh when Seth was 26.

It's still gives 200+ lifespan before the flood but makes the gap between the two periods much narrower.

Disclaimer: the suggestions comes from "Genesis. A New Light On The Origins Of Man, the Earth, and the Universe" by fr. Guido Bortoluzzi.

  • Very interesting! Does Bortoluzzi speculate as to why the Bible switched from counting seasons to years? Commented Sep 11, 2015 at 17:14
  • I don't remember him giving any other biblical arguments.
    – MirMasej
    Commented Sep 11, 2015 at 17:25
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    Nice answer and welcome to the Christianity Stack Exchange! When you get a chance, you may what to read up on how this site is a little different than most other sites. This is not a comment on the quality of your answer, but rather a standard welcome message.
    – ThaddeusB
    Commented Sep 11, 2015 at 17:26
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    The problem with the "seasons" explanation is the nearly smooth curve decrease rate doesn't quite handle a jump of 4 to 1.
    – Joshua
    Commented Aug 11, 2019 at 18:54

There are several ways we can find a biblical basis for the reduction in lifespans, at different levels from the literal to the literary.

At least in part, a biblical literal explanation is in Genesis 6:3, where God ordained that henceforth humans will not live beyond 120 years:

Genesis 6:3 (NIV): Then the LORD said, “My Spirit will not contend with humans forever, for they are mortal; their days will be a hundred and twenty years.”

A likely literary example can be found by comparing the lifespan of Adam, the first person in the Book of Genesis, with that of Joseph, the last person in the Book of Genesis. Adam is portrayed as living for 930 years, which is (30 x 30 + 30). Joseph is portrayed as living for 110 years, which is (10 x 10 + 10). The ancients were fascinated with numerology, and it could be argued that the biblical genealogies are literary examples of this.

  • Yes, the description of ancient ages were often literary devices as you say, with more important people being ascribed longer ages to mark their significance
    – Kevin
    Commented Oct 19, 2020 at 17:53

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