Phys.org has an article on dental changes associated with the transition from hunter-gatherer cultures to less mobile agricultural ones. The transition occured 10,000 to 12,000 years ago at the end of the Paleolithic period. Some quotes:
“Our findings show that the hunter gatherer populations have an almost “perfect harmony” between their lower jaws and teeth,” he explains. “But this harmony begins to fade when you examine the lower jaws and teeth of the earliest farmers”.
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The diet of the hunter-gatherer was based on “hard” foods like wild uncooked vegetables and meat, while the staple diet of the sedentary farmer is based on “soft” cooked or processed foods like cereals and legumes. With soft cooked foods there is less of a requirement for chewing which in turn lessens the size of the jaws but without a corresponding reduction in the dimensions of the teeth, there is no adequate space in the jaws and this often results in malocclusion and dental crowding.
You can read the original research report in PLOS One.
Steve Parker, M.D.