Why is it that our ancestors in Old Testament times lived so much longer than we do now? Some of our first fathers lived well over 900 years and then gradually decreased with time. I’ve thought that perhaps it was because they needed extra time to fill the earth with sons and daughters.
We understand from the writings of Nephi that the early descendents of Adam and Eve were granted extended lives by the Lord that they might repent while in the flesh. I know nothing about extra time being granted to them in order to increase the earth’s population.
And after Adam and Eve had partaken of the forbidden fruit they were driven out of the garden of Eden, to till the earth.
And they have brought forth children; yea, even the family of all the earth.
And the days of the children of men were prolonged, according to the will of God, that they might repent while in the flesh; wherefore, their state became a state of probation, and their time was lengthened, according to the commandments which the Lord God gave unto the children of men. For he gave commandment that all men must repent; for he showed unto all men that they were lost, because of the transgression of their parents (2 Nephi 2:19-21).