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