The Documentary Hypothesis teaches that the Pentateuch arose from four distinct sources known as JEDP (the Jahwist, Elohist, Deuteronomic, and Priestly source). The J document is usually given a 9th century date, the E source is believed to be an 8th century source, whereas D is attributed a 7th century date and P is considered a 6th century source.
"The Documentary Hypothesis claims that the Pentateuch is a composite of four separate, complete, and coherent documents." See http://imp.lss.wisc.edu/~rltroxel/Intro/hypoth.html
One point that interests me for now is how dogmatic that proponents of this view have been or continue to be. Furthermore, the Documentary Hypothesis is a lesson in how certain scholars get pushed to the margins if they do not follow the status quo. Tremper Longman III and Raymond B. Dillard relate the story of Franz Delitzsch, who apparently was pushed to the margins of scholarship because he did not accept the Documentary Hypothesis. While I understand the need for the scholarly guild to protect academic biblical studies from "loony" and unsupported ideas, it's somewhat disturbing that scholars have made the Documentary Hypothesis (a very speculative endeavor) a touchstone for who can have a voice in the biblical scholarly world and who cannot. That view strikes me as conformist to the utmost degree.
I am reminded of ancient controversies that used force instead of persuasion to shut "heretics" down; and one can't help but think of Martin Werner, whose views on Christ qua angel were intensely criticized by Wilhelm Michaelis. Werner never recovered from the latter's analysis. See https://www.academia.edu/2202637/Reconsidering_and_Aspect_of_the_Title_Kyrios_in_Light_of_4Q416_2_iii
You can believe what you want to believe in academic biblical studies, so long as your view harmonizes with the prevailing orthodoxy.