Welcome to the final case study of the Paleo Diet module. We're going to step away from the chemical approaches but stick with the teeth. And stick is an appropriate word as we will learn how caries, you'll know these as cavities, are related to sticky sugars and starches. And thus can tell us about what people were eating in the past. To understand how caries can be used for certain aspects of the diet, we have to first learn how and why they form. When you were a child you probably had a grown-up tell you not to eat too many sweets because they'll rot your teeth. And indeed this is true. Caries are caused by bacterial breakdown, essentially the fermentation of carbohydrates, these includes sugars and starches on the tooth�s hard surface. This bacterial fermentation create an acidic microenvironment, which causes the hard surface to demineralize. Oral bacteria collect around the teeth and gums in a sticky mask called plaque. Some areas of the mouth collect plaque more easily than others, something you may have observed when at the dentist.� Grooves on the chewing surfaces on the back of your teeth let plaque by bacteria hide in trapped food particles, and the same is true for the spaces between adjoining teeth. Hence the frequent occurrence of caries in these locations. So what you may be asking is, knowing that caries frequencies are likely to be higher when the diet is high in carbohydrates, can we really use this information to better understand the diets of past peoples? In order to provide some context to answer this question, we should first be aware of the results of several meta-analyses conducted by different researchers over the years. A meta-analysis is simply the compilation of the results of the whole bunch of studies. These meta-analyses have compared caries frequency rates of populations with different subsistence types as seen in this table. Generally, hunter, gatherers show low caries frequencies whereas people with mixed economies, gardening and farming show increasingly higher caries rates. But notice there is quite some variation within each category. It depends not only on subsistence strategy but also on the specific foods you consume. And other important factors are the rate at which teeth are worn as this can raise caries. If there is any form of oral hygiene or how the food is prepared. The softness and stickiness of a food is very important. There are also clear genetic differences in the predisposition and differences between males and females due to the effect of different hormones. On a grand scale, however, it's clear that agriculturists have higher rates of caries than any other subsistence category. To explore one of these agricultural groups, we turned to the Maya region of Central America. Here the agriculture cropping to caries is maize where you probably know as corn. In particular, we're studying a variety of maize that rose around 4,000 years ago that was softer and sweeter and thus more cariogenic than its earlier native form. One interesting case study is researched on by Dr. Christine White and colleagues at the Maya site of Lamanai located here in modern day Belize. This site yielded human dental remains from 1250 BC to AD 1000, a time span of over 2000 years. After AD 1000, the Maya's civilization became refraction of what it once was. With some saying there is a collapse of their civilization. This would have changed many aspects of Mayan life including Maya agriculture. So as you can see in the Late Preclassic, Early Classic, and Late Classic periods the frequency occurrence was somewhat similar at 20, 24, and 18%. As expected with me is at state of food. But in the final classic period caries frequency dropped dramatically to only 1.8%, this was proposed to be due to a dramatic decline in maize consumption. And later stable isotope research indeed found this to be the case, with Terminal Classic peoples having different stable carbon isotope values that showed maize, a C4 plant, was not as heavily consumed. It was likely replaced by a mixture of wild and domestic C3 plants. Another example from the Maya region comes from two sites. Copan in modern day Honduras investigated by doctors Reed and Whittington, and again Lamanai and Belize. And here the interesting findings relate especially to skeletons from the classic periods. So from 8250 to 950, at Copan at this period the elites were found to have a lower prevalence of caries than ordinary people. Among low status burials there were significantly more caries than in high status individuals. At Lamanai there were two elite burials from the wealthiest tombs and these individuals had no caries whatsoever. This suggest that the elite had access to and consumed more animal protein. Again, subsequent isotopic analyses of bone collagen supported this finding. Lower status Maya individual consumed more maize. Clearly in the Maya world one's status played an important role in what was deemed appropriate to eat and what was made available to eat. So you think that this is the case today as well? You'll find one of the online forum discussion questions, asks you to think about the role of status or class in food availability and choices in your country or region of the world, other foods generally, only in by the wealthy and if so, what are they? Or conversely are there foods that are considered to be associated with the lower class? Perhaps giving quaint labels such as rustic, peasant food or even poor people's food. Maybe in thinking about this you'll come to realize that your own food choices are informed by some unconscious paradigms about what foods are and are not appropriate for you socio-economic status. In this week's video, you've learned about how dental caries are related to certain dietary variables, particularly the proportion of carbohydrates versus protein in the diet. We�ve then looked at the few brief examples from the ancient Mayans, Central America, to show how differences in caries frequencies are indicative of a different diet. Coming up next is the short summary video about Paleo Diet where we'll bring it back to some of the big questions. And after that, we'll move onto week four. All about how your teeth and bones reveal a lot about the activities you commonly engage in.
