Composition of the Torah

According to a long-standing tradition, the five books of the Torah were dictated by God to Moses.  However, after the Christian Reformation of the 16^th century, modern critical biblical scholarship found that the Pentateuch did not seem to be a unified text like you would expect from a single author like Moses.  As a result, the unique Mosaic authorship of the Torah has been largely rejected by leading biblical scholars since the 17^th century as they came to realize that the Torah was involved in a long evolutionary process.  Some later scholars started a critical study of the various parallel accounts, inconsistencies, and changes in style and vocabulary within the Torah.  The first attempt was to see two different sources, one that called God “Yahweh” and the other that called God “Elohim.”  Deuteronomy was different with its own source.  Finally, the Elohim source was divided again with a priestly source as the final redactor.  In 1878, the German Julius Wellhausen (1844-1918) published his history of Israel that established the four-source theory for the Torah.  The first source, the Jahwist (J) source, was the earliest document, a product of 10th century BCE and the court of Solomon.  The second source, the Elohist (E) source, was from the 9th century BCE in the northern Kingdom of Israel.  This E was combined with J by an editor to form a JE document.  The Deuteronomist (D) third source, was a product of the 7^th century BCE, during the reign of King Josiah (640-609 BCE).  Finally, the Priestly (P) source was a product of the priest-and-temple dominated world of the 6^th century BCE.  The final redaction, was when P combined with JED to produce the Torah as we now know it.  During the second half of the 20^th century, some scholars questioned the age of J, so that they thought that it should be moved to the time of the Babylonian captivity, 597–539 BCE.  This meant that the dates and even the existence of the other three sources came into question.  Thus, the final redaction of the Torah might have been during the Persian rule between 450–350 BCE.  Was this nothing more than a compilation of short, independent narratives, which were gradually brought together into larger units in two editorial phases, the older Deuteronomic and the more recent Priestly phases?  Most scholars today continue to recognize Deuteronomy as a source, with its origin in the law-code produced at the court of King Josiah.  They also agree that some form of a P source existed, although its extent, especially its end-point, is uncertain.  The general trend in recent biblical scholarship is to recognize that the final form of the Torah as a literary and ideological unity was based on earlier sources, likely completed during the Persian period.  Thus, the final composition of the Torah came in the 5^th century BCE.  Of course, some of the traditions contributing to this narrative are older, since allusions to the exodus story were made by 8^th century BCE prophets such as Amos and Hosea.  This story may have originated a few centuries earlier, perhaps in the 9^th or 10^th century BCE.  There are signs that it took different forms in Israel, in the Transjordan region and in the southern Kingdom of Judah before being unified in the Persian era.  This exodus narrative was most likely further altered and expanded under the influence of the return from the Babylonian captivity in the 6^th century BCE.  When you think that the Torah was written?