Was Genesis written in the 5th and 6th centuries BC or much earlier?
The book of Genesis is written much earlier than in the fifth and sixth centuries BC. The traditional view of the authorship of Genesis is that it was written as one of the first five books of the Bible, the Torah or Pentateuch. The author is Moses.
If we hold this to be true in traditional Christianity, then that is much too late of a date for the book. It is understood that Moses wrote the book of Genesis sometime during the 40 years in the wilderness wanderings. This is around 1400 BC.
Only in recent human and church history, since about the 19th century and especially in the 20th century, have scholars begun to question the authorship and dating of most if not all of the Bible books. Critical scholarship has introduced an entirely new set of disciplines from textual to literary criticism, and everything in between.
Some of critical scholarship can be helpful to the believer. One of the biggest problems with critical scholarship is that much of it is produced by unbelieving scholars. Their goal is to rip up the text of Scripture rather than come to it with a believing heart and mind.
Sometimes this can be helpful and other times it produces many words and pages that are useless to the message of the Bible. Many critical scholars have an agenda of tearing down Scripture rather than allowing it to build us up.
It is from these disciplines of critical scholarship that the date and authorship of every Bible book have been challenged. Sometimes the challenges are fanciful at best. Many times they are pure gasses as to when the actual date and to the authors are. One thing they do not do is take Scripture at face value and trust that it is inspired of God and does not lie to us.
One of the critical approaches to the authorship of the first five books, including Genesis, is that Moses cannot have written it. The reason they give, among others, is that one person cannot write more than one genre in one book, or subgenres. This is a crazy idea considering that most authors do this.
They cut up the first five books of the Bible into four different types of literature from priestly literature to law literature. They suggest that Moses could not have written law and one section of a book and then priestly material in the next.
But Moses and all writers are smarter than the scholars think. I myself write different genres and types of literature even within the same books and pieces. This makes no sense. Moses surely could have written everything that was written by him in these first five books.
We must also note that Moses did not come up with all of the material all by himself. What I mean by this is that Moses used documents and sources before his time. He was not there at the beginning of creation or during the time before the flood. But he had books of genealogies and other documents that he used by God’s divine inspiration in the writing of the Pentateuch.
So if you are a believing Christian, not a critical scholar who may not even believe in the words or inspiration of the Bible, Moses is the most likely author. And if that is the case, it must be written during his lifetime.