Survival of the Sickest summary

Understanding Diseases Through Evolution

In Survival of the Sickest, Sharon Moalem puts forward an intriguing theory: some conditions we see as diseases may actually be beneficial genetic adaptations. Derived from our ancestors' efforts to survive various environmental challenges, these "conditions" may have once served a life-saving purpose.

The book begins by discussing how hemochromatosis, a disorder causing iron overload, might have been protective against the plague. The Yersinia pestis bacterium, which causes the plague, needs iron to survive. Those with hemochromatosis deprive the bacterium of iron, possibly giving them a survival advantage.

Exploring Unusual Adaptations

Moalem also discusses diabetes, suggesting it might be an inherited adaptation for surviving in cold climates. Frozen climates render glucose unavailable to cells, simulating insulin resistance — a condition characteristic of diabetes. So, our ancestors with a propensity for diabetes may have been better equipped to survive the Ice Age.

Moving on from individual conditions, Moalem explores the phenomenon of "epigenetic inheritance," where environmental factors lead to genetic changes that can be passed down generations without altering DNA sequences. The Dutch Hunger Winter during World War II is cited as an example where mothers who were starved gave birth to offspring with altered health outcomes, demonstrating the effects of environmental exposure on genetic expression.

Implications of Evolved Diseases

Moalem asserts that understanding diseases as evolutionary adaptations could have profound implications for their treatment. Because diseases like hemochromatosis and diabetes were once beneficial, he suggests that removing them completely might have unforeseen consequences, inclining towards management rather than outright eradication.

A discussion on aging and the so-called longevity genes dazzles readers as another radical idea is introduced. He suggests that natural selection favors anything that helps us reach the age of reproduction and that once this task is completed, there's no evolutionary advantage to living longer. In fact, aging and eventual death might be evolution's way of ensuring genetic diversity and the survival of the species.

Viewing Health Through Evolutionary Lens

The final part of Survival of the Sickest concerns viruses and their interplay with our genome. It raises the speculation that viral DNA could be integrated into our own, potentially impacting our evolution. Moalem ends on a note emphasizing the importance of safeguarding our environment, as the diseases and conditions we face are directly linked to our ecological legacy.

In essence, this enlightening exploration forces readers to rethink widely held beliefs about health and disease. It underscores the intricate bond between our health, genetic predisposition, and environmental factors, shedding light on how these connections are forged over centuries of human evolution.