Our ancestors’ habitat remained stable for a long time because climate fluctuations were low and their food and supply were secure. The first evidence of bipedalism and different species of Hominini, which differed only slightly in terms of nutrition and brain size over more than five Ma , appeared seven Ma ago. The extensive food spectrum consisted mainly of plant-based (terrestrial and aquatic) foods. Here, some micronutrients were also scarce but sufficient for the other phenotype and more uncertain, resulting in limited food quality. Paranthropus boisei disappeared about 1 Maa ago when Homo erectus, the ancestor of Homo sapiens, had already begun to hunt and thus improved his food quality. It is not certain whether the vegan diet or other factors caused the extinction of P. boisei. However, new evidence has shown that P. boisei mainly ate plants. For modern humans, a vegan diet does not correspond to their evolutionary roots. The consequences of a long-term plant-based diet with an insufficient supply of micronutrients are manifold, affecting not only the immune system but also the development of children before and after birth.