Grit may not have been added directly to the meal but it comes in from the mill itself.
The grit ground off the mortar and pestle goes into the flour. If you have enough skulls from a population you can get relative ages from the amount of tooth wear caused by that grit.
Not sure if it answers this or not but I remember discussing osteoclasts in Anatomy which is a factor in braces for teeth. This seems to me would be the process by which the body would reabsorb bone and free up calcium but I don’t know if this can actually happen with teeth.
I still say its a bit of a leap to conclude tooth wear is cuased by grit in the flour. People have tooth wear today, and there is a lot less grit in the flour, I would think.
Ah, but you haven’t seen the molars of a person who spent his life eating hand-ground breadstuffs. Nor will you, since I’m too cheap to subcribe to the pertinent journals.
And here is a collection of systems for rating tooth wear: http://www.nd.edu/~stephens/toothwear.html Sure, we all wear down our teeth but I don’t suppose you’ve see molars with the enamel worn clean through and the dentin worn flat.