User blog comment:Maki Kuronami/Extra Lesson: Attack on Grimm/@comment-24994749-20141017003507/@comment-10380701-20141017004338

To be fair, they specifically mention "ancient cultures". For all we know, the ancient tribes of Remnant may worship Dust as gods as well.

I mean, as of now, Dust is pretty much the most concrete thing in-series to worship. It's either that or an abstract god.