Problem Set 1

Question 1

What is the bottom line of Dr. Nesse’s lecture?

Answer 1

The bottom line is that understanding human health and disease requires an evolutionary perspective in addition to traditional medical approaches.

• While medicine often focuses on proximate causes (the mechanisms of disease), evolutionary explanations reveal why the body is vulnerable to certain diseases.
• Natural selection has shaped the human body not for perfect health but for reproductive success, leading to trade-offs that explain many health issues.
• Disease vulnerability results from factors like slow evolutionary responses, trade-offs between traits, and the body’s adaptation to environments that no longer exist.
• Therefore, applying evolutionary theory to medicine is crucial for understanding why diseases exist and how to approach them more effectively.

Question 2

Are there any current uses of evolutionary theory applied to medicine or health sciences? If so name some.

Answer 2

• Antibiotic resistance
• Evolutionary genetics
• Human phylogeny

Question 3

What other aspects of evolutionary theory could be useful to understand and treat so called “illneses”?

Answer 3

• Natural Selection: Understanding how certain traits may have been advantageous in ancestral environments can explain why certain diseases manifest today.
• Mismatch Theory: This theory posits that many modern health issues arise from a mismatch between our evolved biology and contemporary lifestyles (e.g., obesity in a high-calorie environment).
• Life History Theory: This can help explain trade-offs in health and development, such as the balance between growth, reproduction, and longevity.

Question 4

Name some common misconceptions about evolutionary theory. Explain.

Answer 4

“Survival of the Fittest” Means Only the Strong Survive: This phrase often misinterprets fitness as strength; in reality, fitness refers to reproductive success.

Evolution is a Linear Process: Many believe evolution is a straight line from simple to complex organisms, but it is more accurately a branching tree with many paths.

Humans are the Pinnacle of Evolution: Evolution does not have a goal; all species are adapted to their environments, and no species is “better” than another.

Question 5

Why are there aspects of our biology that are so imperfect or that are so prone to make us ‘suffer’?

Answer 5

1. Mismatch:
   - Our bodies were never designed to cope with out modern lifestyle environment
   - Selection is slow
   - The mismatch explains most chronic diseases
   - Our fulfilled desires are killing us (car crashes, smoking, etc.)
2. Competition with fast evolving organisms
   - pathogens evolve faster
   - Also predators and conspecifics
   - Selection is constrained
3. Every trait is a tradeoff
   - Sickle-cell
4. Constraints on natural selection
   - Path dependence
   - Mutation
   - Weakness of selection
   - happenstance
   - We misunderstand
5. Organism shaped for reproduction, not health
   - Selection maximizes reproductive success NOT health, longevity and happiness
   - Reproduction trumps all: Senescence (some genes that cause aging have no selective cost in the wild, others offer advantages early in life when selection is stronger), the feeble sex
6. Defenses and suffering
   - Nausea, vomiting, diarrhea, fever, cough, fatigue, anxiety are painful but useful responses

Question 6

What are the differences between pathology, an uncomfortable adaptation, a constraint, and a cost paid for earlier adaptations? Does the distinction really matter for practice?

Answer 6

Pathology: Branch of medical science that studies the causes, mechanisms, and effects of disease.

Uncomfortable Adaptation: Traits that may not be optimal but serve a purpose (e.g., anxiety as a response to danger).

Constraint: Limitations imposed by our evolutionary history that prevent optimal adaptations (e.g., bipedalism leading to back pain).

Cost of Earlier Adaptations: Trade-offs that arise from adaptations that were beneficial in the past but may not be advantageous now (e.g., high-fat storage in times of food scarcity).

The distinction matters in practice as it helps clinicians understand whether to treat a condition as a disease or to recognize it as a natural variation that may not require intervention.

Question 7

Can the same individual be healthy and sick?

Answer 7

Yes, an individual can exhibit both health and sickness simultaneously. For example, a person may have a chronic condition (like diabetes) but still lead a healthy lifestyle and maintain good overall health.

Question 8

Should therapeutic intervention be limited to conditions that jeopardize biological adaptation?

Answer 8

Therapeutic interventions should not be limited solely to conditions that jeopardize biological adaptation. While it is important to consider evolutionary implications, many conditions that do not threaten survival can significantly impact quality of life and well-being, warranting treatment.

Question 9

Should understanding that something is “natural” tell us if it right or wrong, or whether or not it should be treated?

Answer 9

Understanding that something is “natural” should not automatically dictate its moral rightness or whether it should be treated. Natural does not equate to good or desirable; many natural processes (like disease) can be harmful. Ethical considerations, individual circumstances, and societal values should guide treatment decisions.