Why are the men of Genesis so old? Were the dating systems just different? Are all of these old ages supposed to have symbolic meaning? Genesis 5:3-32 ESV spends a great deal of time describing the age of the men in Adam's lineage through Seth.  Why are the men of Genesis so old? Were the dating systems just different? Are all of these old ages supposed to have symbolic meaning? Why does the Bible focus on the age at which they had one child in particular, and then how much time passed until each died?

&quot;When Adam had lived 130 years, he fathered a son in his own likeness, after his image, and named him Seth. The days of Adam after he fathered Seth were 800 years; and he had other sons and daughters. Thus all the days that Adam lived were 930 years, and he died.
&quot;When Seth had lived 105 years, he fathered Enosh.  Seth lived after he fathered Enosh 807 years and had other sons and daughters.  Thus all the days of Seth were 912 years, and he died.
&quot;When Enosh had lived 90 years, he fathered Kenan.  Enosh lived after he fathered Kenan 815 years and had other sons and daughters.  Thus all the days of Enosh were 905 years, and he died.
&quot;When Kenan had lived 70 years, he fathered Mahalalel.  Kenan lived after he fathered Mahalalel 840 years and had other sons and daughters.  Thus all the days of Kenan were 910 years, and he died.
&quot;When Mahalalel had lived 65 years, he fathered Jared.  Mahalalel lived after he fathered Jared 830 years and had other sons and daughters.  Thus all the days of Mahalalel were 895 years, and he died.
&quot;When Jared had lived 162 years he fathered Enoch. Jared lived after he fathered Enoch 800 years and had other sons and daughters. Thus all the days of Jared were 962 years, and he died.
&quot;When Enoch had lived 65 years, he fathered Methuselah. Enoch walked with God after he fathered Methuselah 300 years and had other sons and daughters. Thus all the days of Enoch were 365 years. Enoch walked with God, and he was not,for God took him.
&quot;When Methuselah had lived 187 years, he fathered Lamech. Methuselah lived after he fathered Lamech 782 years and had other sons and daughters. Thus all the days of Methuselah were 969 years, and he died.
&quot;When Lamech had lived 182 years, he fathered a son and called his name Noah, saying, “Out of the ground that the Lord has cursed, this one shall bring us relief from our work and from the painful toil of our hands.” Lamech lived after he fathered Noah 595 years and had other sons and daughters. Thus all the days of Lamech were 777 years, and he died.
&quot;After Noah was 500 years old, Noah fathered Shem, Ham, and Japheth.&quot;
This is a great question.  The Bible never provides a direct rationale for the seemingly long ages recorded in the Old Testament.  It just states them as a matter of fact with no apology for them.

As we look more closely at the ages, though, we find some very interesting things.  The ages fall quite dramatically at a very definite point in biblical history and decline quite rapidly to ranges that fit our current experience.  This fall actually corresponds to the flood of Noah recorded in Genesis 6-8.  

On a side note, it seems that Methuselah, Noah's grandfather, died in the year of the flood, while his father died some time before the flood.  As Noah's was the righteous line, Methuselah is not thought to have died in the flood, but shortly before the flood.  The name Methuselah actually means "his death shall bring judgment".



There is biblical evidence that this catastrophic event significantly changed the earth's climate in many ways.  Indeed, we are told that prior to the flood, there was no rain, but that a mist arose and watered the earth instead.  


  Now no shrub of the field was yet in the earth, and no plant of the field had yet sprouted, for the Lord God had not sent rain upon the earth, and there was no man to cultivate the ground. 6 But a mist used to rise from the earth and water the whole surface of the ground.  Genesis 2:5-6 NASB


The flood may have been the first instance of rain at all on the earth.  So, if this is accurate, then the pre-flood climate may have been much much healthier than it was afterward.  Plants would have grown much more quickly and been much more fruitful as well, and this would have been able to provide a plentiful food supply for larger animals.

If that is so, then that would explain many things that we find today:


Wooly mammoths frozen with fresh grass still in their mouths
tropical plants buried beneath many layers of ice in arctic regions
skeletons of mankind that are enormous (giants mentioned in Genesis)
Cave drawings and other depictions of dinosaurs, all created by mankind.


After the flood, as I mentioned before, we find lifespans plummeting to ranges within what we would expect today.

Prior to the flood, the wickedness of man had apparently risen to such a high degree that the only way God saw to remedy the situation was to basically start over with just one family.  


  Then the Lord saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually. 6 The Lord was sorry that He had made man on the earth, and He was grieved in His heart. 7 The Lord said, “I will blot out man whom I have created from the face of the land, from man to animals to creeping things and to birds of the sky; for I am sorry that I have made them.” 8 But Noah found favor in the eyes of the Lord.  Genesis 6:5-8


Some have suggested that God shortened the lifespans to prevent people from having time to descend to that level of depravity again, and this certainly is consistent with the biblical record. 

Conclusion

So, the ages along with other information suggest a pre-flood climate that was extremely healthy and quite different from that post-flood climate.  The ages drop significantly after the flood to levels similar to that of today.