Human life has been shortened by about a half, several times. The longest any man lived after the flood was Heber who lived 464 years, a little more than half of Methuselah's age, 969 years, the longest before or since the flood. The longest time man lived after the dispersion at Babel was Reu who lived 239 years, a little more than half of Heber's age. In the wilderness, life was again shortened to about half of the age of Abram (Psa. 90:1010The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labor and sorrow; for it is soon cut off, and we fly away. (Psalm 90:10)). The blessed Lord was cut off in the "midst" or half of His days, as a man (Psa. 102:2424I said, O my God, take me not away in the midst of my days: thy years are throughout all generations. (Psalm 102:24)).
Scripture furnishes no account of the birth or death of any of Cain's posterity, but simply records their doings (Gen. 4).
Seth, third son of Adam, in whom the line of grace was continued, was contemporary with all the antediluvian fathers except Noah.
Methuselah was contemporary with Adam for more than 200 years, and with Noah for about 600 years.
Enoch, who walked with God, was contemporary with Adam for about 300 years, and with Noah for some time, and thus the truth and revelation of God then revealed, was handed down for 1656 years.