The first eleven chapters, which give us the primeval history (universal history) of the world, do so by relating five stories that all have the same structure. The stories are of the fall, Cain, the sons of God marrying the daughters of man, the flood, and the tower of Babel. All five stories follow this fourfold theological pattern: a) Sin: the sin is described; b) Speech: there is a speech by God announcing the penalty; c) Grace: God brings grace to the situation to ease the misery due to sin, and d) Punishment: God punishes the sin.
These patterns arise from the Author of Genesis not by mistake, but I believe, by divine purpose so that we better understand the purpose and context of Genesis. Though I do hold, Genesis 1 was written at a different time than the rest, I firmly believe the compilers picked up where the others left off (if it was not the very same ones).
The author of Genesis began by bunting the polytheism of his world and replacing it with the reality and truth of God’s monotheistic theology. So then, how did the author’s hearers understand the days of creation as he read them the account? Certainly, they did not understand it as myth! It was a polemic against the pagan mythologies of the surrounding nations. Each day of creation attacks one of the gods in the pagan pantheons of the day and declares that they are not gods at all. On day one the gods of light and darkness are dismissed. On day two, the gods of sky and sea. On day three, the earth gods and gods of vegetation. On day four, the sun, moon, and star gods. Days five and six dispense with the ideas of divinity within the animal kingdom. Finally, it is made clear that humans and humanity are not divine, while also teaching that all, from the greatest to the least, are made in the image of God. Thus Biblical reality replaced myth.
This begins the plentiful and wonderful theological motifs of Genesis. Chaos into order, darkness into light and so on. We find Genesis to be the Primeval reality Israel was longing for as they exited slavery from Egypt. A grand return to their God, the one true God of all creation.