The Mishnah (Brachos 6:1) says that anything that comes from the ground gets a Ha'adamah, except for bread, which gets a Hamotzi. Well, what about non-bread foods from the Five Grains? The Gemara (36b) says that Mezonos was instituted by Rav and Shmuel.
What brachah did the Tannaim make on those foods that we now make a Mezonos on? Did they make a Ha'adamah, since they're from the ground? Did they make a Hamotzi, and they equated all of the Five Grains to bread? Or did they make a Shehakol, since it's ground up beyond the point of recognition, or because that's the standard nondescript Brachah if nothing else fits (and it fits all foods, at least bedieved)? I would assume the last category as least likely, that these foods are worse off than Ha'adamah, and for the same reason I don't think not making a brachah is even an option.
I'm not sure if it's possible to answer this question, but I'm really curious if there's an answer out there.