A dentist/anthropologist named Weston A. Price wrote "Nutrition and Physical Degeneration" in mid-20th-century based on research he did in various parts of the world. He studied paired groups of people, closely related ethnically.One of the groups would live close to easy access to commercially manufactured foods, while the other would be isolated in some way so that had to rely on more traditional foods, including that grown by themselves.
Most were relatively primitive people, but also included an isolated, Roman Catholic Swiss farming community and their non-isolated nearby relatives who had easy access to "white bread" type foods.
He found extreme differences in dental arches, skull and skeletal structures as well as susceptibility to many diseases including diabetes and tuberculosis, though it was not known at the time that tuberculosis is contagious. His research methods may not have satisfied those of today, but were very convincing, more so in fact than today's sometimes very small reported differences.
The book is available at Amazon, and there is a website dedicated to his work. The website IMO has gone overboard, though I doubt any of their food choices would be unhealthy.
Left: [Fijians] The development of the facial bones determines the size and shape of the palate and the size of the nasal passages. Note the strength of the neck of the men above and the well-proportioned faces of the girls below. Such faces are usually associated with properly proportioned bodies. Tooth decay is rare in these mouths so long as they use an adequate selection of native foods.