"Survival of the Sickest" by Dr. Sharon Moalem and Jonathan Prince explores the paradox of why harmful genetic diseases persist in human populations by revealing their evolutionary advantages. The book highlights hemochromatosis—a disorder causing excessive iron absorption—as an example where a deadly trait may have protected ancestors from infections like the bubonic plague by starving bacteria of iron, ensuring survival during epidemics. The text underscores iron's dual role in health and disease, explaining how excess iron fuels pathogens while regulated levels bolster immunity, as seen in historical bloodletting practices that modern medicine now employs to treat hemochromatosis. The authors also examine other evolutionary adaptations, such as diabetes-like mechanisms in wood frogs to survive freezing temperatures, skin color variations balancing vitamin D synthesis and UV protection, and the alcohol flush reaction in Asians acting as a deterrent against alcoholism. These examples illustrate how genetic traits, though detrimental today, once provided critical survival benefits, showcasing evolution's complex interplay with health.

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