Book excerpt: Human illnesses can be understood as damage to those adaptations that we took on at various stages in our evolution from pre-life molecules to modern Homo sapiens. Preventing these illnesses entails avoiding what causes the damage — which too frequently are the everyday hazards of twenty-first-century life, as the chart below shows: Level of Evolution / Cause of adaptive failure / resulting disease or problem Pre-life / Environmental poisons / Certain birth defects Single cell (bacteria and amoeba-like) / Viral infection / Colds/flu/HIV Morula (sponge-like) / Cellular stress / Cancer Chordate / Physical stress / Back pain Fish / Excess dietary salt / Hypertension/heart disease Amphibian / Tobacco smoke / Lung cancer/emphysema Lower primate / Excess dietary sugar / Diabetes mellitus Higher primate / Vitamin C deficiency / Scurvy Ape / Excess dietary protein / Gout Homo sapiens / Reduced dietary variety / Nutritionaldiseases/food allergies