Genesis 5:1

This is the book of the generations of Adam. In the day that God created man, in the likeness of God made he him;

1. It sounds like Adam may have kept a record of his posterity, from which these chapters of Genesis were copied or summarized.
2. Adam and/or his descendants apparently used a written language.
3. God created man (previously stated).
4. Man is in the likeness of God (previously stated).
5. The repetition of these concepts suggests the first 4 chapters of Genesis were written by a different person than wrote chapter 5.