Genesis 4 records the story of Cain and Abel. The sacrifices of Cain and Abel provide a contrast.
Cain brought only crops as an offering. In the Biblical sense, plants do not have life (plants do not have blood - see Lev 17:11), and thus Cain's offering did not involve any death. Thus, it was counterfeit. It did not symbolize the fact that death is required for the atonement of sin.
Abel offered animals on his altar. This was an acceptable sacrifice. Why?
Thus, here in Genesis, at the start of history, we have a contrast:
Cain is an example of man-made religion. People try to get to God their own way. They're perhaps offended by the gory details of Leviticus, or by the teaching that the Lord Jesus purchased our pardon with his own blood, (but they don't mind killing unborn babies!). Cain eventually killed Abel, who was a man of God. Abel is commended in Heb 11:4 as a hero of faith.
When God confronts Cain about his murder of Abel, he shows no remorse. He asks, "Am I my brother's keeper?" God in effect answers, yes! Cain's wife must have been a sister or close relative. Cain's descendants also seem to have been the first to build cities (Ge 4:17). The term city here does not imply a metropolis, but a settlement with a watch.
While the Bible mentions only three sons of Adam and Eve by name, it does mention that they had many sons and daughters (Ge 5:4). Jewish tradition has it that Adam had 33 sons and 27 daughters. So you can imagine that the population would increase rapidly, and Cain had good reason to be wary.
Cain went away from God's presence, and in whatever little the Bible mentions about his descendants, nothing is mentioned about their having any interest in God. Cain's descendants were quite illustrious, developing music, agriculture, and metallurgy.
The first few generations had certain advantages:-
These factors contributed to the great advancement of technology in the ante-diluvian (pre-flood) world. The same factors also contributed to the proliferation of evil. There seems to have been no government then - everyone fended for themselves (see Ge 4:23).
Genesis 5 tells us about the sons of Adam. It's interesting to check the meanings of their names:-
Thus: "Man is appointed mortal sorrow but the blessed God will come down preaching that His death will bring the sorrowing comfort". There's the gospel!
In this construction, "Methuselah" refers to the death of the Lord Jesus Christ that would be a ransom for us. However, in a more immediate context, Methuselah's name referred to the fact that his death would bring God's judgment. Methuselah died in the year of Noah's flood. Notice also that at 969, Methuselah is the longest living human recorded! Does this not suggest the forbearance of God? He does not want to punish man!! God waits for as long as He can.
"As I live, declares the Lord Jehovah, I take no delight in the death of the wicked, but that the wicked turn from his way and live. Turn! Turn from your evil ways!" - Eze 33:11
Enoch (Methuselah's father) probably understood the import of his son's name. He was very godly, he walked with God and God raptured Him. Thus, Enoch is a symbol of the church that will be raptured away before God's wrath is poured on the earth, while Noah is a symbol of Israel, that will be purged even as she passes through the time of God's judgment. Enoch also prophesied about God's judgments that are yet future (Jude/Judas 1:14).
This chapter begins with verses that have been the subject of much discussion:
"Now it came to pass, when men began to multiply on the face of the earth, and daughters were born to them, that the sons of God saw the daughters of men, that they were pleasing; and they took wives for themselves of all whom they chose." - Ge 6:1,2
What exactly is this talking about? There are two interpretations that believers tend to have:-
Position # 1:
The "sons of God" are angels. These are rebellious angels who took on human bodies and, for the sake of pleasure, married women. The Bible mentions "giants" as the result of such unions, suggesting that these angels may have tried some tinkering with the human gene code. If this is so, other departures from the normal human body can also be expected.
Position # 2:
The "sons of God" refers to the people of the godly line of Seth - they intermarried with the daughters of men - the ungodly women of Cainite descent.
Arguments in favor of position # 1 (or against position # 2):
Arguments in support of Position # 2
The following arguments are used to support position # 2, but I don't consider them valid.
Argument # 1: "In Mk 12:25, the Lord Jesus says that angels do not marry."
But wait a minute. He's talking about the "angels of God in heaven" at the time of the resurrection. These are the "good guys" who have not rebelled against God and taken human bodies for themselves. That it is -possible- for an angel to take on a human body is made evident in Genesis 18 and 19. Abraham and Lot get angelic visitors who appeared just like men. They ate and drank with Abraham and Lot, and the Sodomites thought they could have a sex orgy with them.
Argument # 2: "The proliferation of evil that followed these marriages suggests that it was a case of God's people marrying the people of the world, the unequal yoke that God forbids in 2 Cor 6:14"
It is true that unequal yokes (marriages between believers and unbelievers) don't make for good families, and the children of such marriages are likely to go astray. However, this does not constitute proof for position # 2, since it is equally possible that marriages between rebellious angels and ordinary (unbelieving) women would result in delinquent children.
Believers should not behave like evolutionists, offering one interpretation of the known facts as evidence for a position, when there are interpretations for the same facts that support the opposite position!
Whatever be the case, God was displeased with all the evil and decided to destroy the earth with Noah's Flood.