Mismatch occurs when organisms that

Mismatch occurs when organisms that were well adapted to one set of environmental circumstances cannot evolve rapidly enough to adapt to a new set of circumstances. Of the big ideas in evolutionary medicine, mismatch is one often invoked but frequently misused. For example, many people concerned with nutrition and exercise as components of a healthful lifestyle like to imagine an ancient environment, generically called the environment of evolutionary adaptation or "EEA," to which we were once well adapted and deviations from which are the cause of the "diseases of civilization" that we now experience: obesity, cardiovascular disease, diabetes, autoimmune diseases, and allergies, not to mention anxiety, depression, psychosis, and other mental disorders.