Paleolithic people had uniformly excellent teeth: archaeology shows that tooth decay is extremely rare before the Neolithic.  Read Weston A. Price's "Nutrition and Physical Degeneration" for many examples, including agricultural societies whose nutrition and dietary practice was sufficient to prevent caries.

There are most likely several factors influencing this:

1. For many thousands of years, grain was ground with stones.  That means there was a lot of sand and stone chips in the grain, which caused tooth wear.

2. The nutrient that allows us to grow strong teeth, and even regrow lost dentin (vitamin K2-MK4) is only present in the organ meats and bone marrow of animals (or in unpasteurized, grass-fed dairy fat).

3. As Paul pointed out, chewing tough, fibrous meat and plants during childhood causes teeth to become stronger.  Eating grain-based gruel (and drinking beer) doesn't.

4. Mouth bacteria feed on sugar and starch.  A diet high in simple sugars and starches encourages tooth decay.

JS

PS: ubetido, I'm glad you're asking questions -- but the volume is becoming difficult to deal with, and answering you is taking a meaningful amount of my time and energy.  I'd greatly appreciate it if you reciprocated by buying a copy of The Gnoll Credo.  (If you have no interest in reading it, just pass it on to someone who might.)  Thank you!

ubetido:

I don't like having a "Donate" button because it puts a price on my advice, as well as implying fee for service.  Just pick up a copy of TGC through whatever retailer is convenient for you. 

If you're in the USA, I encourage you to get a signed copy from my publisher (though Amazon and B&N also work).  Here's a list of places that ship for free to the rest of the world: The Book Depository is reliable.  Worst case: you can donate it to your local library if you don't like it.

Do stick around!  I'm glad you're posting to the forums, instead of peppering me with emails, so that others can get the benefit of the exchange.

JS