I say this as someone with a passion for milling and experimental archeology: I imagine they had degraded teeth because of two factors: stone querns can deposit grit into the grist and unless you're manually sorting everything twice, it's easy to miss seed-sized stones in your grain. Ultimately, I think this is why white flour became a status good after milling became professional--the end result is sifted obviating both issues simultaneously.

Something that doesn't get talked about often enough is that grain and seeds become easier to mill (and digest) after toasting (aka parching). There is less percussive force required to mill toasted grain which deposits less grit into your grist.

If you look into the history of military rations, you universally find parched grain. The Confederates parched corn, the Maoists parched rice, the Prussians parched peas, the Israelites parched barley and wheat. I don't imagine that neolithic humans or Neanderthals lacked this technology. I also suspect this is why we find charred grain (not only as a result of survival bias)--someone got distracted during the parching process and they threw out the burnt results. Multitasking has always been a bad idea.

Unfortunately, European-derived cultures are so downstream of professional milling that the ultimate role of parching grain in the agrarian revolution has been lost in the popular mind.

This is totally understandable given that for centuries in Europe it was broadly illegal for peasants to mill their own grain. The feudally-entitled miller was actually allowed to destroy any querns that he found to prevent defection.