However, clean water and modern hygienic advances have made such infections rare in developed countries. For example, throughout human evolutionary history, we’ve been more or less continually infected by parasites, such as helminth worms. Some cases are relatively obvious - for example, the high rates of lactose intolerance among human populations without a history of dairying and the prevalence of type 2 diabetes among populations that have recently adopted a high-sugar, high-fat Western diet. However, because these dietary changes happened relatively recently (and in the modern world, occurred in conjunction with advances in dentistry that lessened their impact on health and reproduction), we do not possess adaptations to deal with an influx of sugar and starch and, hence, are likely to develop dental disease.Įvolutionary mismatches to modern lifestyles seem to contribute to many diseases. If we humans had eaten lots of carbohydrates throughout our evolutionary history (for many hundreds of generations) and if the resulting dental disease had reduced our ability to survive and reproduce, we might have experienced natural selection favoring adaptations that reduced the severity of the problem. In these instances, natural selection has not been able to keep pace with the rate at which human culture and the innovations that it generates (e.g., farming) change. The idea is that our bodies are ‘matched’ to the environment in which we spent most of our evolutionary history - not to the environment that we have created for ourselves today. The link between our diet and rates of tooth decay and gum disease is an example of a mismatch to modernity - a case in which a disease results from a modern lifestyle feature that our lineage has not experienced during the course of our evolutionary history. Since greater biodiversity is associated with healthy, resilient ecosystems, a lack of oral biodiversity may help explain the high rates of dental disease among modern humans. As with many other habitats on Earth, there just aren’t as many species living in our mouths as there used to be. Second, as these dietary changes occurred, the diversity of the oral ecosystem plummeted. When humans began eating processed flour and sugar, the ecosystem shifted again, this time favoring decay-causing species. When humans began farming and eating more wheat and barley, the oral ecosystem changed, allowing gum-disease-causing species to flourish. First, different bacterial species became more common after dietary shifts. The scientists collected tartar samples from the teeth of human skeletons ranging from a few hundred to more than 6000 years old and extracted the ancient bacterial DNA, providing snapshots of the oral ecosystem at different points in our history. To study the ancient microbial communities inhabiting human mouths, an international team of researchers capitalized on the fact that oral bacteria are trapped on teeth by tartar buildup. Information on controversies in the public arena relating to evolution.Alignment with the Next Generation Science Standards.The big issues – Pacing, diversity, complexity, and trends.Macroevolution – Evolution above the species level.Microevolution – Evolution within a population.
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