Myths should be taken seriously, not literally. That’s how one finds the truths hidden within the myth.
In Genesis, Chapter 1, God creates the universe in 6 days, by the power of his word, and all he makes is good. He creates man and woman and gives them perfect liberty; he tells them to go forth and fill the earth; he gives them dominion over all animals and the unrestricted use of all plants bearing seed. He is the god of liberty.
In Chapter 2, while God rests on the seventh day, Lord God builds a garden around the tree the Knowledge of Good and Evil and the Tree of Life; builds Adam and animals from mud; and then makes Eve out of Adam’s rib. Lord God is obviously a lesser god; he doesn’t create matter; he forms it into other things, as men do. His name proclaims his purpose: to rule men as their Lord. He is the god of government, of necessary evil.
He starts by forbidding them to eat of the fruit of the Tree of Knowledge of Good and Evil: they can eat of all the other trees in the garden, but if they eat of that tree, in that day they will surely die. His servant, the serpent, then tempts Eve into eating the forbidden fruit, saying that they won’t die; they will gain knowledge. And so it was; the Lord God lied and the serpent spoke truth; they learned that they were naked and powerless before the wrath of the Lord God, but they did not die. The Lord God said, “Behold, the man has become as one of us, to know good and evil; and now, lest he put forth his hand and take also of the Tree of Life, and eat, and live forever:” he evicted them from the garden.
Thus Lord God imbued his creation with conscience and sent them forth into a world of people without it. Adam’s first two sons came to blows, with Cain killing Abel in a jealous rage; Cain’s conscience and his resulting guilt caused him to lie to the Lord about his knowledge of Abel’s whereabouts. Cain is exiled and finds a wife among the daughters of the first creation. Adam has one more son, Seth, and no daughters. Seth also finds a wife from the daughters of other men, so the line of Adam is mixed from the start: men of conscience and those who lack it.
The world was still full of conscienceless people, and thus became full of evil, as evil exists regardless of whether one knows it to be evil. God decided that mankind needed to be destroyed apart from the family of Noah, a direct descendant of Adam who found favor with the Lord. The flood kills the remaining unmixed people of the original creation and leaves only the mixed breed of Adam’s line through Noah. Most of their descendants have some conscience; some lack it entirely; in all it is limited; and nobody’s perfect.