The problem and solution has been known for almost a century now; check out the book 'Nutrition and Physical Degeneration' by Weston Price. 'The Dental Diet' is also solid reading.
I'm still working through the book, but the tl;dr is that it mostly just comes down to nutritional deficiency. People in the past ate pretty much strictly nutrient-dense foods, people today eat a lot of junk food, empty carbs, and generally foods that just aren't nutrient dense compared to what our ancestors ate (mostly vegetables and meats).
I'm still working through the book, but the tl;dr is that it mostly just comes down to nutritional deficiency. People in the past ate pretty much strictly nutrient-dense foods, people today eat a lot of junk food, empty carbs, and generally foods that just aren't nutrient dense compared to what our ancestors ate (mostly vegetables and meats).