The Lifespan of Man

Updated: Sep 4, 2019

In 2012, life expectancy in the United States hit a record high: 78.8 years.1 While this may be an achievement in our day, we know with Bible in hand that man used to live much longer. Genesis records mankind living nearly 1,000 years (the oldest man being Methuselah at 969 – Genesis 5:27). Naturally, the question arises: why doesn’t man live this long anymore?

We first look to Scripture for an answer. Genesis 6:3 appears to deal with the subject: And the Lord said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years. This “declaration” may seem to indicate that God set an age limitation of 120 years, thus accounting for why we live much shorter lives. It may initially satisfy our inquiry, until however, we consider the genealogy of man after the Flood. It’s imperative to note that the verse in question precedes the Flood.

Arphaxad, born to Shem two years after the Flood, and thus long after the supposed lifespan-reducing declaration, died at 438 years. His son Salah lived 433 years. Eber lived to 464. It’s clear that after the declaration, man was living well beyond 120 years, and this was still true at the time of the Patriarchs: Abraham died at 175, Isaac at 180, and Jacob at 147. Had God intended to limit man’s life to 120 years, one would reason that these men would not have lived much beyond that span. It may be argued that God chose to implement this decree gradually over time. This could be so, but it seems to this writer a short-reaching explanation, posing the question as to why this would be done gradually. If the intention of Genesis 6:3 was to limit man to 120 years of life, why then did man continue to live well beyond 120 years? 

It is, however, important to note that man’s years were indeed shortening. Various explanations have been proposed as to the reason for this, pointing to pre-Flood and post-Flood differences in the amount of oxygen in the atmosphere and radiation reaching the earth’s surface. One suggested  answer is an interesting one – genetics, namely, a shortening of the gene pool.2 We well assume that Adam and Eve had perfect genetics, but because of the necessary consanguineous (inter-family) marriage to relatives, these perfections were altered as further generations were born and inter-married one another. (Might it be possible these complications were first seen with Noah’s father Lamech? He died at 777 years, making him a “youngster” when compared to his forefathers and his son Noah, who died at 950.) 

We see this shortening of the gene pool, called a genetic bottleneck, twice in Genesis: after the Flood, and after the dispersion at the Tower of Babel. After the Flood, there were only eight people left on the earth to repopulate. When the languages were confused at Babel, the Bible says that the Lord scattered them abroad from thence upon the face of all the earth (Genesis 11:8). Those of the same tongue would naturally join together and separate from the others, beginning communities of their own in different parts of the earth, thus producing offspring from a smaller pool of genetics.  

The role of genetics may account for the fact that Noah still lived 350 years after the flood. Had environmental or atmospheric changes been responsible for a shortening of mankind’s lifespan, one might expect Noah to not have lived his “full term” like his fathers before the Flood (Noah lived to the age of 950 – Genesis 9:28-29). Genetics may also account for the steady decline in lifespans as further generations were born. The only time we see a drastic and sudden reduction in lifespans occurs after the Flood and after the Tower of Babel, where the variable that changed was the size of the gene pool. (This is apparent when a genealogy chart is consulted.)

What, then, is the meaning of the 120 years in Genesis 6:3? 120 years were indeed set from the day this was spoken, but we might suggest this stood for the time allowed before the Flood, within which Noah would build the ark. The wickedness of man had waxed great on the earth and warranted complete destruction. The verse reads, My spirit shall not always strive with man, for that he also is flesh (in that we know that “flesh” and “sin” are often synonymous… “for that he also is sin”). Noah, who found grace in the eyes of the Lord (Genesis 6:8), was to be spared along with his immediate family and the animal pairs: seven of every clean best, two of every unclean, and seven of the birds. This presented the need for a vessel large enough to contain such a multitude, which required extensive time to build.

There is another thought as to the meaning of Genesis 6:3; that God was allowing a period of 120 years for the people of the world to repent. This too may appear sound until one closely examines the text. God condemned the whole of mankind to death (Genesis 6:12-13), with the exception of Noah and his family. It’s worth noting that Noah was called a preacher of righteousness (2 Peter 2:5), and it may appear that he preached repentance to them, but the wording of the rest of Genesis 6 suggests repentance was not the object of God’s declaration. Verses 17 and 18 record when God first informed Noah: And, behold, I, even I, do bring a flood of waters upon the earth, to destroy all flesh, wherein is the breath of life, from under heaven; and everything that is in the earth shall die. But with thee will I establish my covenant; and thou shalt come into the ark, thou, and thy sons, and thy wife, and thy sons’ wives with thee. These listed were the only ones who were to enter into the ark, and God specified this before Noah even started building the ark. Had God allowed for repentance, might He not have instructed Noah? Complete destruction was foreordained and imminent, and God was going to replenish the earth with the seed of a Godly man. None others were to be allowed on the ark.

It may be a difficult thing to grasp that God would not allow space for repentance. This is complicated even more so by the assumption that the wicked knew of the judgement to come. The assumption is sound, for surely the people saw the ark during its construction and enquired of Noah as to what it meant, and it’s reasonable to conclude that Noah did not hide God’s revelation from them. Mankind must have known what God told Noah. Following this line of thought, it might also appear odd that not a single person repented after 120 years of such knowledge. This is not a stunning outcome as we know the power and deceitfulness of sin, added to the fact that the Lord God had not caused it to rain upon the earth… But there went up a mist from the earth, and watered the whole face of the ground (Genesis 2:5-6). They had never known water to come down from above, and being wicked and evil hearted (Genesis 6:5-6), were therefore without proof sufficient for strong belief. But again, could there truly have been no space for repentance?  

Perhaps the incident of Lot and Sodom and Gomorrah can shed some light on this, as it shares many similarities. Like Noah, Lot was a righteous man who dwelt amongst sinners (2 Peter 2:7-8). Destruction was foretold for the cities, and we have no record of allowance for their repentance. Again, the language and nature of the account strongly suggests that destruction was determined, especially when considering the plea of Abraham in Genesis 18 for the angels to spare the city, through which we understand their intent to destroy it. Was the city never preached to then? We might imagine Lot, having been a righteous man, would have attempted to turn the people away from their sins, but their hearts were so given to sin that recovery wasn’t feasible. There was time to repent, but the time for such action was before the sentence. Having a righteous man in their midst to consider, like Noah or Lot, might have stood for proof enough that there was a way that was favorable to God, but they would not have it. There comes a point when sinful man must be “given up,” as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient (Romans 1:28). One could say that the “cup of their iniquity” was full and the sentence was final. The angels told Lot, …we will destroy this place, because the cry of them is waxen great before the face of the Lord; and the Lord hath sent us to destroy it (Genesis 19:13). So, like the Flood account, only Lot and the family members he could gather were rescued from the destruction to come.

The present writer concludes, then, that the 120 years of Genesis 6 were intended as sufficient time for Noah to build the ark and prepare for its occupants. It seems only reasonable that Noah would have warned the people of their coming destruction, but they indulged in their sins and had set their hearts so contrary to God that they would not, and therefore could not, be recovered. How, then, was Noah a preacher of righteousness? Although there was no room to repent after God had announced His plan for the Flood, it’s probable Noah preached to them before the threat; while life continued as normal. Another answer lies in the necessary role he would play in instructing the generations to come out of him. His children were fully grown, but they would still benefit from his instruction. More importantly, their children would also require education. They needed to be taught and brought to adulthood, and Noah, a man loved by God, would certainly bring them up in the nurture and admonition of the Lord (Ephesians 6:4), instructing them in righteousness.

Although Genesis 6:3 is not a limitation on mankind’s lifespan, it does appear that God did in fact determine to shorten their lifespan. God said that the imagination of man’s heart is evil from his youth (Genesis 8:21), and the more time afforded to a man would mean more wickedness. It is thought by some that given more time, man would eventually see the fault in his ways, but often it has been shown that when one knows that there is much time to do something, rarely is it attended to promptly. Procrastination is the notable route in such a case. But give a man a short deadline and promptness is more likely to ensue. Yet, even considering mankind’s more limited amount of time on earth in these latter days, it still stands true that man that is born of a woman is of few days, and full of trouble (Job 14:1).

The actual reason and/or cause as to why our years have been shortened is not stated in Scripture. Certainly, God intended it to happen, but how exactly it was accomplished remains obscure. Perhaps genetic bottlenecks and disorders are the answer. But, even though this appears a plausible solution, the scriptural evidence is such that an absolute stance cannot be taken. 

There is, however, Scripture that speaks to the average span of a man’s life. In Psalm 90:10 we have the words of Moses: The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away. Under the law of Moses, an Israelite could expect an average of 70 years on the earth, and if they were strong, 80 or more. And so it remains to this day.


Tanner Hawkins, Protem, MO

  1. Copeland, Larry. “Life Expectancy in the USA Hits a Record High.” USA Today. October 09, 2014.

  2. Hodge, Bodie. “Why Did People Start to Have Shorter Lives After the Flood?” Answers in Genesis. July 16, 2010.