The Book of Genesis in the Bible is the first book of the Law of Moses (Jewish Torah). While some have tried to argue differently, Moses is clearly the one chosen by God to put the Genesis into the form we have today. However, I like the discussion of Henry Morris in “The Genesis Record” where he outlines how Genesis may, in fact, be a compilation by Moses of the written accounts of the patriarchs. That is, the written records of Adam, Seth, Noah, Isaac, Jacob, and others that were passed down through the generations to Moses who then took these records and combined them into a single whole under the inspiration of God. Morris’ basis of this is to look at how Genesis is divided into sections by the common phrase “the generations of” that appears at the end of each section. Morris’ divisions are

1. “The generations of the heavens and the earth” (Genesis 1:1-2:4). Section written by God and/or given to Adam.
2. “The book of the generations of Adam” (Genesis 2:4b-5:1). Written by Adam.
3. “The generations of Noah” (Genesis 5:1b-6:9). Written by Noah.
4. “The generations of the sons of Noah” (Genesis 6:9b-10:1). Written collectively by Noah’s sons, Shem, Ham, and Japheth and includes the description of Noah’s Flood through the death of Noah.
5. “The generations of Shem” (Genesis 10:1b-11:10) Written by Shem.
6. “The generations of Terah” (Genesis 11:10b-11:27) Written by Terah (Abraham’s father).
7. “The generations of Isaac” (Genesis 11:27b-25:19) Written by Isaac (and includes a section written by Ishmael, 25:12-18)
8. “The generations of Jacob” (Genesis 25:19b-37:2) Written by Jacob (and includes a section written by Esau and possibly a section added later by Moses — the kings of Edom)
9. “The generations of sons of Jacob” (Genesis 37:2b-Exodus 1:1) Written by the sons of Jacob. Most of this is the story of Joseph so most may have been written by Joseph in Egypt.

While this is not directly provable from Scripture, I think this makes very good sense and seems to explain a lot about how this critical piece of the history of mankind came to Moses.