The most traditional way of understanding the chief theme of this fourth chapter of the Book of Genesis is to see it as the beginning of the two peoples, the two nations; the people of God and the people of the world – the seed of Adam, through which the Messiah would come and the church of the New Testament would emerge in due time, and also the seed of the serpent, that is those who are ungodly and who reject God and reject his grace. This is a cable that runs throughout the Bible from beginning to end.
`The wonder of childbirth must have dawned on them as they now brought a child into the world and should still fill us with wonder today. The creative work of God is involved in every new life, but here they experienced God’s gift of being able to bring new life into the world without any direct miraculous intervention on his part. So the command to fill the earth is still in force, even after the fall, and they begin to obey it.