Dietary fibre is the most important factor that modulates human biology and speciation. A low intake of dietary fibre with a diet rich in protein and fat leads to increased endosymbiotic and colonic archaeal growth and neanderthalisation of the species. This leads to induction of the Warburg phenotype and increased incidence of metabolic syndrome x, neurodegeneration, autoimmune disease, cancer, schizophrenia and autism. A high intake of dietary fibre leads to predominant large intestinal digestion by colonic microflora and inhibits endosymbiotic and colonic archaeal growth producing homo sapienisation of the species. This leads to decreased archaeal growth and incidence of civilizational disease. Thus civilizational diseases like autoimmune disease, metabolic syndrome, cancer, schizophrenia, autism and neurodegeneration can be controlled by a high fibre diet, inhibiting archaeal growth, archaeal endosymbiosis and by promotion of large intestinal digestion.