Evolution of symbiotic relationships of the gut and introduction of mismatches affecting those relationships. In this diagram, a cascading series of timelines are shown, with lowest magnification, starting at 600 MYA (million years ago) on top. The timeline with the highest magnification, starting at 200 YA (years ago) is shown on the bottom. The approach used to estimate time of appearance of various symbiotic relationships during evolutionary history (top timeline) in the gut is described in the text. The evolutionary mismatches shown in the bottom timeline apply to communities with widespread systems hygiene [11] and to individuals with highly processed diets [49]