Why is the natural always first and then the spiritual in the Bible?

Les teaches that this is a rule of thumb: you always have first the natural, and then the spiritual, ever since the beginning of human experience. He illustrates it with Cain the natural, then Abel the spiritual; Isaac the natural, then Isaac the spiritual; Esau the natural, and Jacob the spiritual. He says all the genealogies follow that same format—first the natural or non-spiritual, then the spiritual. In Jacob’s life, he was first the natural man, Jacob the deceiver, and then he became the spiritual man, Israel the prince with God. Les connects this to our own experience: we were originally natural, with nothing to do with a spiritual life, but after we are born into the family of God and experience salvation, we are spiritual, citizens of heaven, totally different people. He also says the history of the nation of Israel is divided into the same two categories: those who remain natural, never having spiritual enlightenment even under the covenants, and the spiritual. From the beginning of human history there have primarily been two groups: the lost, the natural element, which are by far the greatest number, and the believers, the saved of the ages, the spiritual. It is the same today: saved or unsaved, regardless of black or white, rich or poor, bond or free.