Why We Get Sick: Using Evolutionary Medicine to Understand Disease

Introduction

• Despite human success, many diseases like cancer, heart disease, anxiety, depression, diabetes, and obesity affect us.
• Evolutionary medicine seeks to understand why our bodies are vulnerable to disease.
• Focuses on why our bodies were shaped in ways that make us susceptible.

Six Reasons for Disease Vulnerability

Mismatch

• Environments today differ significantly from those in which we evolved.
• Evolution of organisms lags behind rapid environmental changes.
• Lifestyle changes such as different food availability and sedentary lifestyles contribute to chronic diseases.

Coevolution

• Humans evolved alongside microorganisms like bacteria and viruses.
• Microorganisms evolve rapidly, often overcoming our defenses quickly.
• Example: Antibiotic resistance in bacteria.

Trade-offs

• Evolutionary changes often come with costs.
• Example: High blood pressure benefits exercise ability but damages tissues later.
• Humans lost body hair for cooling but increased UV exposure risk.

Constraints on Natural Selection

• Natural selection can only modify existing structures.
• Example: The laryngeal nerve in giraffes demonstrates evolutionary constraints.
• Once a structure developed, it's difficult to start over.

Reproductive Success at a Cost to Health

• Natural selection promotes traits impacting reproductive success, not necessarily health.
• Some traits beneficial for reproduction may harm health, e.g., testosterone.
• Diseases affecting reproduction face strong selection, unlike those affecting post-reproductive health.

Defenses and Suffering as Adaptations

• Bodily responses like coughing and fever are defensive adaptations.
• Sometimes, these defenses are misregulated, causing issues like excessive anxiety.
• Defensive responses can be mistaken for disease symptoms.

Complexity of Disease

• Diseases are complex and can arise from multiple causes.
• Example: Atherosclerosis involves mismatch and immune system trade-offs.

Importance of Evolutionary Medicine

• Understanding disease vulnerability through evolution can improve prevention and treatment.
• Evolutionary medicine provides insights into improving health.

Research and Resources

• Arizona State University’s Center for Evolution and Medicine leads research in the field.
• Offers educational resources on evolutionary medicine.
• Visit EvMedReview.com for updates.

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• Images used from Wikimedia Commons.
• Example image: San people by Aino Tuominen.