Recently there was a meeting of the American Association of Physical Anthropologists. Here are some fascinating research areas that were reported during the conference....
When Europeans began to arrive in what became the Eastern US the Natives thought they were dirty and unhealthy looking. Which was true. Their hygiene was worse than the natives and their diets were much poorer. They were also used to being peasants and servants, many of them, with all the connotations especially of that first word.
Well of course, generally speaking, dental health will decline when you are consuming sugars (or compounds broken down to sugars in the mouth) - that's what causes tooth decay in the first place. Not to mention the aggregation of humans and livestock promotes disease. If you find this interesting at all, you should really read Guns, Germs, and Steel; this is, to a large extent, the things talked about in the book (it is less about 'history' as it is about some of those things you mentioned)
