Evolutionary medicine

[20][21][22][23][24] Prolonged periods of inactivity may have only occurred in early humans following illness or injury, so a modern sedentary lifestyle may continuously cue the body to trigger life preserving metabolic and stress-related responses such as inflammation, and some theorize that this causes chronic diseases.

"Microorganisms and macroorganisms such as helminths from mud, animals, and feces play a critical role in driving immunoregulation" (Rook, 2012[26]).

As noted in the table below, adaptationist hypotheses regarding the etiology of psychological disorders are often based on analogies with evolutionary perspectives on medicine and physiological dysfunctions (see in particular, Randy Nesse and George C. Williams' book Why We Get Sick).

[63] Summary based on information in Buss (2011),[64] Gaulin & McBurney (2004),[65] Workman & Reader (2004)[66] See several topic areas, and the associated references, below.

It seeks explanations for diseases, or their symptoms, signs, and cause in single, materialistic— i.e., anatomical or structural (e.g., in genes and their products)— changes within the body, wrought directly (linearly), for example, by infectious, toxic, or traumatic agents.

An important theoretical development was Nikolaas Tinbergen's distinction made originally in ethology between evolutionary and proximate mechanisms.

[75] Randolph M. Nesse summarizes its relevance to medicine: all biological traits need two kinds of explanation, both proximate and evolutionary.

[76]The paper of Paul Ewald in 1980, "Evolutionary Biology and the Treatment of Signs and Symptoms of Infectious Disease",[77] and that of Williams and Nesse in 1991, "The Dawn of Darwinian Medicine"[78] were key developments.

The latter paper "draw a favorable reception",[43]page x and led to a book, Why We Get Sick (published as Evolution and healing in the UK).

In 2000, Paul Sherman hypothesised that morning sickness could be an adaptation that protects the developing fetus from foodborne illnesses, some of which can cause miscarriage or birth defects, such as listeriosis and toxoplasmosis.