What was Shelob, and more importantly, what was Ungoliant?

[The Might]

As far as this "result of natural forces" theory is concerned I can see why you would reffer to Bombadil as such and as I stated above I can also well think of Ungoliant as another such result as well.
Indeed there is no clear proof for this, however, in absence of any other better thery for her origin I personally also share Gwathagor's opinion.

[Gwathagor]

Originally Posted by The Might

As far as this "result of natural forces" theory is concerned I can see why you would reffer to Bombadil as such and as I stated above I can also well think of Ungoliant as another such result as well.
Indeed there is no clear proof for this, however, in absence of any other better thery for her origin I personally also share Gwathagor's opinion.

The proof is not very clear, I agree, but it is both a reasonable and functional theory. My primary reason for viewing Ungoliant as a manifestation of dark natural forces (anti-Bombadil) is the bit in the Silmarillion that describes her as being descended from the darkness that lay about Arda. It's not much, but it works.