I misspoke. Shoulda said "resembling its present form." I still think the conventional wisdom is that it changed a *lot*.
My impression is that there isn't much that is pretty well accepted about this, even among conservative scholars. It looks to me like the "preferred" mechanics of formation of the pentateuch get rewritten about every 50 years, and then the new theory gets discredited.
Oh my bet is they didn't spend much time in the desert per se, just moving around and not directly into the Canaanite settlements where they would not have been welcome, in fact probably just get thrown into servitude. There was a lot of open country in those days, and in fact there still is, and much of it looks very desert-like (worse now than 3000 years ago though), so open to all kinds of guessing. Not a lot of archeological evidence, but its growing (and the article I mentioned is an example).
But it is still a surprise to me that they hung out in the desert so long, even though it was apparent that they were afraid to enter into Canaan.
My analysis is that it is extremely rare to develop anything more than a cult if you try to create a religion from scratch. You can't draw people in unless you work from what they know. Jesus was creating a new sect of Judaism, not a new religion. Its inconceivable that the Israelites did not draw upon the existing pantheon of Gods, traditions and morals (!). I do give them credit though for having really put *monotheism* on the map, because all these other religions were polytheistic. Yahweh in form, description and powers bears tremendous similarity to the Canaanite Gods (who were derived from Ur, Sumaria, etc. etc.), but somewhere along the way it became important that he be the only God, and the others needed to be denegrated.
The tendency of folks to advocate that the Hebrew monotheism was stolen in some flavor from neighboring cultures is common.
That's what the books say, but my previous paragraph is the explanation for why the books say that.
The Biblical story of God being a "jealous" God, not to mention the First commandment, suggests that the simplest story is the Biblical one. God consistently reminded His people that He was not enthusiastic about their dalliances with other dieties.... And it seemd to make God grumpy regularly.
Grumpy, jealous, wrathful, gee whiz is this guy difficult to keep happy...and don't get me started about Abraham...