After the story of Cain’s fall, the author uses the contrasting accounts of Cain’s descendants and Seth’s descendants to take us forward to the time of Noah.  Cain leaves the area where he has farmed and goes into exile in the land of Nod where he marries and starts a family.  In 4:16-24 we read the names and short histories of five generations of his descendants.  Chapter 5 then goes back to Adam and records nine generations of his descendants through his son Seth.  The histories of each line contrast as one side serves the Lord and one does not.  Seth and Cain are both sons of Adam who fulfill God’s command to fill the earth, yet their legacies could not be more different.

The Line of Cain (4:16-24)
God sends Cain out from His presence and Cain goes east to the land of Nod (yes, it is a real place and not just where sleepy little kids go).  Since he is sentenced to wander the earth as a vagrant, it could be that he does not settle here as much as live a nomadic existence here (Nod means “wandering”).

Something to notice throughout Genesis is the significance of the direction ‘east’.  To move east typically means to go away from God.  Adam and Eve move east when they are expelled from the garden.  Can goes further east after his fall.  The descendants of Noah who build the Tower of Babel first journey east.  Lot chooses the eastern lands when he and Abraham decide to go their separate ways.  For whatever reason, going east is rarely a good thing.  Either bad things happen as a result of moving east (Babel, Sodom/Gomorrah) or people go east into exile as a result of disobeying God.

Cain marries and begins a family (thus showing that God’s assurance that he would not be killed in fact comes true).  Obviously this presupposes that Adam and Eve have had multiple children who have had children and so on.  Cain apparently marries a close relative – perhaps even a sister (and even if he does not, someone in the family must in order to multiply).  It is important to understand, however, that this early in man’s existence there is no genetic danger to intra-family unions.

Chapter 4 lists six generations of Cain’s descendants: Enoch, Irad, Mehujael, Methushael, Lamech, and the four children of Lamech.  Verse 17 says a city is built for and named after Enoch.  The subject of the statement is not clear (even though some English translations make it sound as if Cain is the builder).  Either Cain builds the city for Enoch or Enoch builds the city for himself.  If Cain builds it, it would seem to violate his punishment that said he would forever wander.  However, it could be that Cain builds the city but does not settle in it.  When God pronounced that Cain would be a vagrant, it did not seem to be a punishment that Cain could choose to ignore.  Thus it is likely that Cain either does not build the city or does not settle in it.

It is notable that Lamech represents the seventh generation of mankind through Cain (‘seven’ always being a prominent number throughout Scripture).  Lamech seems to show that Cain’s descendants have continued in the sinful ways of their patriarch.  He takes two wives – the first man recorded to do so.  He also tells his two wives that he either has or will murder someone simply for wounding him.  He composes a song to himself simply to declare that he is one bad dude and that he is even more dangerous than his ancestor Cain.  If Cain is avenged sevenfold, then Lamech seventy-sevenfold.  He not only is a violent and murderous man, he is proud of it.

Interestingly, Lamech’s four children contribute much to the culture.  Jabal becomes the father of those who dwell in tents and have livestock (he seems to go beyond what Abel did as a shepherd – Jabal has livestock that includes more than sheep).  Jubal (Adah apparently does not like to work too hard at coming up with names for her sons – perhaps if a third son had been born she would have named him ‘Jobal’?) becomes the father of all those who play the lyre and pipe.  And Tubal-Cain becomes a forger of implements of bronze and iron.  As for Naamah – Lamech’s daughter – some rabbinic traditions hold that she becomes Noah’s wife (note that in the 2014 movie, Noah’s wife was called “Naameh”).  So even though Lamech appears to be a loathsome example of the sinfulness of Cain’s line, his children actually play an important role in human progress generally.

The Birth of Seth (4:25-26)
After listing the descendants of Cain, the story switches back to Adam and Eve.  Eve gives birth to a son and names him Seth.  When he is born, Eve declares that he is the replacement for Abel.  She actually calls him another offspring appointed to her by God.  This seems to be a reference to God’s promise in 3:15 regarding the seed of the woman.  It could be that Eve – after possibly thinking the same thing at Cain’s birth (4:1) – now sees Seth as the promised one.

When Seth has a son of his own – Enosh – people begin to call upon the name of the Lord.  What this means is not entirely clear, but it could mean that more formal worship begins (not that this is the first worship of any kind – see Cain and Abel).  Seth and Enosh and their descendants, therefore, become characterized by their worship of God.  This is a key verse and sets the stage for the genealogy in the next chapter and also serves as a contrast to the line of Cain.

The Line of Seth (5:1-32)
There are several issues to think through when approaching the genealogy listed in Chapter 5.  First, can we take the years listed for the lives of each man literally?  Do the first 10 generations of humans really live for hundreds of years?  Second, can we use the ages listed in this genealogy to compute a rough age for the earth?

To address the first question, there is nothing in the text that suggests we should take the years as anything other than literal.  It is hard to fathom humans living for more than 900 years, but it obviously is a different time and different environment.  It could be that God allows for longer life for the purpose of filling the earth.  With the extremely long lives it is possible for multiple generations to exist at the same time, thus ensuring that the population multiplies relatively quickly.  It also could be that the pre-flood conditions are conducive to longer life as it is after the flood that life spans begin to dramatically decrease.

The second question is not so easy to answer.  Something to keep in mind when going through any genealogy in the Bible is the purpose behind it.  Biblical writers do not always include genealogies strictly for information or to show every generation.  For instance, Jesus’ genealogy in Matthew 1 skips several names for the purpose of showing that there are three sets of 14 generations between Abraham and Jesus.  In fact, in that genealogy, several times it is said that someone fathered someone else when in fact there were two or three generations between them.  In this chapter it is notable that exactly 10 generations are listed – the same number as in Chapter 11.  That makes it seem as if there is some structure to the two genealogies in showing that Noah is the tenth generation from creation and Abram is the tenth generation from Noah.

All this to say, it is probably risky to assume we can count up the number of years listed for the ages of the men in Chapter 5 and come up with how many years after creation the flood occurs, or how old the earth actually is.  It could be that when the text says someone lives for so many years and fathers a son, what it means is that he becomes the father of the line that eventually begets the next name.  Obviously this is all conjecture, but listing exactly 10 generations in both Chapters 5 and 11 makes it appear that having that structure is the goal.  Also, it is notable that righteous Enoch is listed as the seventh descendant of mankind through Seth (5:18), whereas evil Lamech is listed as the seventh descendant through Cain (4:18).  The coincidental contrast seems to be intentional.  It also is important to remember how Moses writes.  It is apparent that he does not in any way try to date the events in Chapter 5.  Like so many things that can be frustrating to the modern reader of Genesis, the age of the earth and the duration of man’s time on it are not addressed by him because they are not important to his purpose.  Thus to assume the genealogies are written sequentially and in the way we would write them is likely dangerous.

That said, however, it is interesting to consider how the lives of the men overlap.  If the generations are sequential, then it means that many of the patriarchs live simultaneously (see attached chart).  For instance, Adam lives long enough to be a contemporary with Noah’s father Lamech, who is born eight generations after him.  Methuselah and his son Lamech apparently die either the same year as the flood or the year before it.  Noah actually is still alive for about a third of Abram’s life even though Abram is born roughly 300 years after the flood.  Shem, Noah’s oldest son who lives through the flood, actually outlives Abram.

The chapter begins with a quick recap of creation.  God created Adam in His own image and made mankind male and female.  He blessed them and named them when He created them.  As man is in God’s image, so Seth is in Adam’s image.  Seth is the chosen descendant of Adam to carry on the image of God.  Seth’s descendants – unlike Cain’s – become the line of promise.  It is through Seth that the promise of 3:15 will be fulfilled.

Adam lives 130 years before Seth is born.  After Seth he lives another 800 years and has other sons and daughters.  He dies at the age of 930 years (Chapter 5’s genealogy is the only one in Genesis that specifically mentions that each man dies – this could be to set up the contrast for Enoch).  Amazingly, this is the last mention of Adam in the text.  He is the first man, the one responsible for sin in the world, the most important human to this point in world history, and yet nothing more is written about his life.  Apparently he does nothing in his 800 years of life after Seth that is important to the story of redemption.

The next notable person in the genealogy is Enoch.  Enoch lives 65 years and fathers Methuselah.  He then lives another 300 years and is taken from the earth by God.  He is righteous and walks with God, so he does not physically die.  The writer of Hebrews says of him – By faith Enoch was taken up so that he should not see death; and he was not found because God took him up; for he obtained the witness that before his being taken up he was pleasing to God (11:5).  Enoch thus becomes the first of two people in the Old Testament to not taste death – Elijah being the other.

As noted above Enoch is the seventh generation of mankind through Seth.  He compares to Lamech, the evil murderer who is the seventh generation of mankind through Cain.  The contrast between the two men could not be more complete and shows the difference between the two lines.  Seth begets a line of those who call upon the name of the Lord while Cain begets a line of those who boast of taking vengeance.

Methuselah is the longest living man on the list, attaining the age of 969.  He seems to do everything later than anyone else as he lives 187 years before having a son.  He shows that righteous Enoch not only avoids death but also leaves to his son the blessing of very long life.

The second to last name on the list is Lamech – not to be confused with the descendant of Cain.  Lamech is notable for being Noah’s father.  When Noah is born Lamech says of him, “This one shall give us rest from our work and from the toil of our hands arising from the ground which the Lord has cursed” (5:29).  It is hard to know exactly how this prophecy is fulfilled.  The flood will not exactly give anyone rest as it will simply wipe everyone out.  Perhaps where it is fulfilled is in Noah’s survival of the flood and the propagation of the line of the Messiah through him and his descendants.  Noah will live to start the world again and continue the line of Seth which will eventually lead to the reversal of God’s curse on creation.

Lamech lives 777 years.  Whether or not it is intentional, his age compares to the seventy-sevenfold vengeance that Lamech the Cainite sang about.  The two Lamechs are thus joined numerically.

Noah is the last name listed.  He lives 500 years and becomes the father of Shem, Ham, and Japheth.  The text does not here say which son is the oldest, but later it will say Ham is the youngest (9:24) and will either say – depending on the translation – that Shem is older than Japheth or Japheth is older than Shem (10:21).  Why Noah lives so long before having sons is not explained.

The Evil of Mankind (6:1-4)
The first four verses of Chapter 6 serve as a bridge between the line of Seth and the flood story.  They set the stage for the flood and explain why a new start is required.

Apparently, while the descendants of Seth walk with God for over 1600 years(!), the rest of mankind devolves into more and more wickedness (which makes the record of Seth’s descendants even more remarkable).  As an example of the wickedness that typifies mankind, some beings called the sons of God intermarry with beautiful daughters of men (it is interesting that the verbiage used in verse 2 to describe how the sons of God see the daughters of men is the same used for how Eve saw the forbidden fruit – 3:6).  No one really knows what this refers to or who the sons of God are.  It could be that they are fallen angels in human form that take wives for themselves and spawn superhuman mighty men of old.  The problem with this interpretation is that angels are said not to intermarry or be sexual beings at all – and it seems odd that God would punish mankind for the angel’s actions.  Another option is that they refer to the righteous descendants of Seth who marry unrighteous women and thus fall into evil.  The problem here is that there is no reason to think these marriages would result in superheroes.  Yet a third possibility is that the sons of God are some kind of royal race whose marriages result in the mighty men.

At the end of the day there is no way to know for certain what this refers to.  It is meant to illustrate the evil on the earth and show why God decides to send the flood.  Verse 4 adds to the confusion by mentioning that a group called the Nephilim are on the earth at this time also.  It is unclear if this means the Nephilim are the product of the marriages – like the mighty men – or that they simply live during the same time.  The Nephilim will later be called giants during Moses and Joshua’s time (Num 13:33) but it is not clear if the Numbers reference is to the same people – who, after all, will die in the flood – or if the cowardly spies who come back from Canaan simply use the name as a reference to show how mighty the men of Canaan are.

God says after witnessing the evil on the earth that mankind’s days shall be one hundred and twenty years.  This means one of two things.  Either the average lifespan of man from here on will be roughly 120 years – which would explain the significantly shorter lives after the flood – or that man has another 120 years to exist before God sends the flood.  It is hard to know which of these is correct as both seem plausible.  Since the average age of man decreases so dramatically after the flood, however, perhaps it is best to assume age is what He refers to.

The Righteousness of Seth/The Faithfulness of God
It is worth noting again what Seth’s genealogy says about the righteousness that apparently is passed down from generation to generation.  Seth and his son Enosh become the first family to formally call upon the name of the Lord (4:26).  As a result, the next seven generations call upon God also.  The descendants stay righteous even in the midst of a dark and wicked world.  As a matter of fact, the world becomes so evil that Seth’s seventh descendant – Noah – is said to be one of the only righteous men in the world.  And Noah – born roughly 900 years after Seth – is described as righteous and blameless for his time (6:9).  NINE HUNDRED YEARS after the righteous patriarch, and the descendant is serving God to the point that he is singled out in the whole world as righteous and blameless.  What an amazing legacy and what an amazing example of God’s goodness and what it means for God to have His hand on a people.

Know therefore that the Lord your God, He is God, the faithful God, who keeps His covenant and His lovingkindness to a thousandth generation with those who love Him and keep His commandments.
– Deut 7:9