rob117

I agree that the Joseph story was probably northern in origin, but it could easily date to any period in the monarchy (although 8th-7th century is most likely IMO, as this is when we have most of our other literary activity). There is no reason why the stories about early northern holy sites could not simply be referring to the fact that these sites actually were some of the earliest holy sites. And Shechem and Shiloh are in Ephraimite rather then Benjaminite territory, so this does not fit with the idea of particulary Benjaminite authorship for these stories; only generalized northern authorship.

It's true that Benjamin must have originally been the southernmost of the Israelite tribes; however a good case can be made that this situation was pre-monarchic. This is the situation spoken of in the Song of Deborah (Judges 5) which mentions 10 Israelite tribes, not 12, and does not include Judah in that count. Baruch Halpern in David's Secret Demons makes a good case for the theory that the integration of the tribe of Judah into the Israelite confederation was a late and complex process, but it did occur, probably just before the monarchic period. The Bible itself admits that Judah was also affiliated with various non-Israelite groups in the Negev such as the Calebites and Jerahmeelites, who were eventually absorbed into that tribe and so Judah would have probably been seen by the northerners as only "half-Israelite." The north thus had a greater claim to the Israelite name than the south; however, this does not negate the fact that Judah ultimately identified itself as belonging to the same ethnicity as the north.

The 8th-century prophets refer to Judah and Israel as one and the same ethnically, and the various false prophecies that these books contain negate seeing them as later pseudepigraphical works. Jeremiah was a Benjaminite living under Judean rule, yet he nowhere refers to his Judean contemporaries as being "non-Israelite."

During the monarchic period, Israel and Judah were rivals, and during the post-exilic period the impetus among the Judean community was to shut out the Samaritans rather than include them. This is not an environment in which the idea of Judah as a member of Israel would have developed had it not already existed.

The evidence for the Josianic reform is wholly internal, yes, but the way the story of the reform is written, it is far more likely to have been written by a contemporary than by someone 100+ years later. The story admits that the Passover was not celebrated in Israel until the time of Josiah. This does not reflect well on the legitimacy of the holiday as celebrated and thus is unlikely to have been written by a non-contemporary who accepted the holiday's legitimacy. Additionally, if such a story were going to be invented by a later writer, it is unlikely that it would be assigned to an otherwise obscure king such as Josiah; it would be more powerful to assign it to a famous king like David or Solomon.