The Righteous Line
The genealogy of Adam through Seth is considered a righteous lineage for a variety of reasons. It was during the life of Seth's son Enos that humans began to call upon or proclaim the name of the Lord (Genesis 4:26).
Enoch, the great, great, great grandson of Seth, was known for "walking with" or having faith in God in a particularly violent time in man's history (Genesis 5:24).
Noah also "walked with God" and was considered one of the three most righteous people to have ever lived (Genesis 6:8 - 9, Ezekiel 14:14, 20). It is also from Seth's descendants that the great patriarchs Abraham, Issac and Jacob are born and from which the tribes of Israel come into existence. Lastly, it is through Seth that Luke traces back Jesus' bloodline from Mary to Adam (Luke 3).
Genealogy Fast Facts
The Bible does not reveal at what age Adam had his firstborn son Cain. We do, however, know when the nine generations after him had their firstborn. The average age at which a patriarch, from Seth to Noah, produced his first male child was close to 158 years old.
The average age at death of the first ten generations of man through Adam and Seth (with the exception of Enoch) is 912 years. How long Enoch lived is unknown, as God transported him away from humans at the age of 365 in order to protect his life.
Top Five Oldest
The top five oldest humans to have ever lived are Methuselah (969 years, Genesis 5:27), Jared (962, verse 20), Noah (950, 9:29), Adam (930, 5:5) and Seth (912, 5:8). Runners up of this exclusive group include Cainan (910, 5:14) and Enos (905, 5:11), with Mahalealel almost making it to 900 by living 895 years (5:17).
A Long Stretch
Adam and Methuselah, two of the five oldest humans, spanned an incredibly long period of time. How long was it? Adam lived to be 930 and overlapped Methuselah's life by more than 240 years. Methuselah died in 2313 B.C. which was the same year God caused the great flood upon the earth. Their two lives spanned the entire time from man's creation to the flood which amounted to 1,656 years!
Golden Age of Pre-Flood Patriarchs
Biblestudy.org's timeline of the Old Testament places the creation of Adam in 3969 B.C. Based on this starting date, there exists an incredibly unique period in the pre-flood history of mankind.
It is between the years 3095 and 3039 B.C., a 56 year period, that the first nine generations of the patriarchs are alive at the same time! Adam, in 3095, is 874 years old. In the same year Seth is 744, Cainan is 549, Methuselah is 187 and Lamech, the father of Noah, is born. Even Enoch, who lived at least to the age of 365, was 252 years old.
Adam is the first of the nine patriarchs alive during this special time to die. His death, in 3039 B.C., was only 126 years shy of the birth of Noah who represented man's tenth generation on earth.
Enoch
Enoch is an exception in the genealogy of Seth as the Bible only states that at age 365 God "took him."
And Enoch walked with God, and then he was not, for God took him (Genesis 5:24, HBFV).
Enoch was not, as some believe, raptured or changed into a spirit being in order to receive his reward in heaven. The privilege of being the first human changed into a spirit and presenting himself before God's heavenly throne belongs exclusively to Jesus Christ, the firstborn of the dead (see John 3:13, Acts 2:29 - 34, Colossians 1:18, etc.).
Enoch was a righteous man living in an unparalleled time of violence and wickedness. God, in his mercy, decided to move Enoch to an unknown location on earth in order to protect him.
Age at the Flood
Noah was 600 years old when the floodwaters came to cleanse the earth of its wickedness (Genesis 7:6). His son Japheth, the firstborn (Genesis 10:21) was 100, Shem was 98 and Ham was in his 90s when they entered the ark. Two years after leaving the ark, when he turned 100, Shem produced his first son Arphaxad (Genesis 11:10).