The human fossil record is pretty short on cavities, as are the rare hunter-gatherer societies still remaining. All these problems arose with the adaptation of agriculture and a processed, grain-based diet.
The fossil record indicates humans began shrinking their brains 30k years ago. The underlying cause of gum disease and virtually all of the inflammatory/degenerative diseases is the retention of excess intracellular iron. There are at least 70 peer reviewed publications from 2014 where researchers from around the globe mentioned iron chelation as a therapeutic option in heart disease, cancer, diabetes, stroke, tbi, ptsd,autoimmune conditions etc. We can currently track the relative gray matter shrinkage in infants from the first bottle of iron fortified formula milk.