Why We Get Sick by Randolph Nesse and George Williams Summary

Why We Get Sick explores how evolutionary biology explains vulnerabilities to diseases like cancer, heart disease, and mental disorders. Authors Randolph Nesse and George Williams argue that traits causing modern illnesses often persisted due to evolutionary trade-offs, such as fever being a defense mechanism or genetic adaptations favoring reproductive success over longevity.

This book is ideal for readers interested in evolutionary biology, medicine, or public health. It offers insights for medical professionals, students, and anyone curious about why humans remain susceptible to diseases despite millennia of natural selection.

Yes—it’s a seminal work in evolutionary medicine, praised for challenging conventional views on disease origins. The book’s blend of scientific rigor and accessible examples, like the “Red Queen Principle,” makes it valuable for understanding health through an evolutionary lens.

The book posits that diseases persist because evolution prioritizes reproductive fitness over perfect health. Traits like inflammation or genetic mutations may have provided survival advantages in ancestral environments but now contribute to modern ailments.

Fever is framed as an evolved defense mechanism to combat infections by raising body temperature, not a direct symptom of illness. Suppressing fevers can inadvertently prolong infections, highlighting the body’s adaptive responses.

This concept describes the evolutionary arms race between hosts and pathogens. Just as the Red Queen in Alice in Wonderland says, “It takes all the running to stay in place,” pathogens and humans continuously adapt to outpace each other, ensuring diseases like the flu persist.

Critics note that some hypotheses lack direct evidence, particularly around mental health disorders. The book’s speculative approach, while thought-provoking, leaves room for further research in emerging evolutionary medicine fields.

Evolutionary mismatches—such as calorie-rich diets clashing with ancient metabolic adaptations—explain rising obesity rates. Our bodies, optimized for scarcity, struggle in environments of abundance and sedentary lifestyles.

Natural selection favors genes that enhance early reproduction over longevity. Traits beneficial in youth, like rapid wound healing, may have trade-offs later, such as increased cancer risk.

It suggests conditions like anxiety and depression may stem from evolved defense mechanisms misaligned with modern stressors. For example, low mood might historically have prevented risky behaviors but now manifests as chronic disorders.

Darwinian medicine uses evolutionary principles to understand disease origins. It examines why natural selection left vulnerabilities, such as childbirth difficulties from bipedalism or wisdom teeth impaction from dietary changes.

As a foundational text, it pioneered the field by framing diseases through evolutionary trade-offs. Unlike niche academic works, it balances scientific depth with readability, making it a gateway to broader evolutionary health literature.