Introduction to Evolutionary Medicine

Introduction to Evolutionary Medicine

• Concept of evolutionary medicine focuses on how evolutionary principles apply to health and disease, integrating insights from biology, anthropology, and medicine. It seeks to understand how evolutionary processes shape human health.

• Highlighting that medicine primarily deals with:

  • Diagnosis: Identifying the underlying causes of diseases by examining symptoms and conducting tests. This involves understanding the biological mechanisms and environmental factors at play.

  • Treatment: Developing strategies to intervene in the disease process. This may include pharmacological treatments, lifestyle changes, and supportive therapies to manage symptoms and improve health outcomes.

  • Prevention: Establishing measures to avoid the onset of diseases by addressing risk factors and promoting healthy behaviors. Public health initiatives play a crucial role in preventive medicine.

Key Questions in Medicine

• Diagnosis: What is causing damage or disease? What functions/pathways are disrupted? Understanding the patient's history, physical symptoms, and diagnostic tests is crucial.

• Treatment: How do we interfere with the entities causing disease? This involves not only targeting infections but also considering chronic diseases and their management.

• Prevention: How do we protect against disease causative agents? This encompasses vaccinations, lifestyle modifications, and public health policies that mitigate risk.

Evolutionary Perspective in Medicine

• Evolutionary Toolbox: This provides deeper insights beyond proximate (how/what) to ultimate (why) questions in health and disease. It enables a better grasp of why certain diseases manifest and persist in populations.

  • Combining evolutionary principles helps in:

  • Better understanding of disease mechanisms by analyzing how human biology has been shaped by our evolutionary past.

  • Providing new insights for diagnostics, treatment, and prevention, potentially leading to more effective strategies that account for evolutionary dynamics.

Distinguishing Evolutionary Medicine from Traditional Medicine

• Evolutionary medicine can answer unique questions compared to traditional medicine, leading to:

  • Understanding why we age and the physiological changes associated with aging.

  • Identifying defenses vs diseases, focusing on the role of symptoms as potential adaptations rather than just harmful effects.

  • Understanding the implications of drug resistance, a growing concern in the treatment of infections and chronic diseases.

Five Reasons for Vulnerability to Disease

1. Trade-Offs

   • Every organism has limited resources (energy, nutrients) impacting evolution and vulnerability to disease. This impacts decisions made by organisms concerning growth, reproduction, and survival.

   • Example: Resource allocation between DNA repair (longevity) and reproduction. An organism may prioritize reproduction over longevity, making it more susceptible to disease later in life.

   • Immunopathology: Strong immune responses can damage host cells alongside fighting pathogens, illustrating a trade-off between immune defense and tissue integrity.

2. Natural Selection and Genetic Fitness

   • Natural selection acts on genes that impact reproductive success, not necessarily overall health. Some genetic traits may predispose individuals to certain diseases without negatively affecting their reproductive fitness.

   • Diseases may exist if they do not affect fitness or are not selected against, leading to a prevalence of seemingly maladaptive traits in certain populations.

3. Signs of Disease as Defenses

   • Symptoms can serve a defense role rather than be purely harmful. They may be evolutionary responses to pathogens or environmental challenges.

   • Example: Understanding immune responses in relation to symptoms like fevers can show adaptive benefits of those signs, such as inhibiting pathogen replication during elevated body temperatures.

4. Environmental Mismatches

   • Humans have rapidly changed their environment, especially in the last 12,000 years (agriculture) and in the last 100 years (modern medicine). This mismatch can lead to health problems that were not present in our ancestral environments.

   • Some traits may have been advantageous in past environments but detrimental in current contexts, such as diet and activity levels.

5. Pathogen Evolution

   • Pathogens evolve much faster than humans due to shorter generation times, which poses a challenge for our immune system to keep up with emerging diseases.

   • This rapid evolution complicates disease management and immunity strategies, necessitating ongoing research into adaptive and preventative measures.

Focus on Vulnerabilities 2 and 3: Case Studies

• Discussing how some symptoms like fever function as defenses, demonstrated with iguanas and their responses to infections.

• Iguanas show behavioral thermoregulation to induce fever, which may help manage bacterial growth and enhance immune response efficacy.

• Further human studies indicate that fevers can enhance immune responses in certain contexts, showing the utility of symptoms in immune function.

Case Study: Myopia and Environmental Influence

• Increasing rates of myopia attributed to reduced outdoor light exposure, suggesting a gene-environment interaction.

• Studies show significant differences in myopia prevalence in populations with different environmental exposures:

  • Older generations vs. younger generations exposed to modern education indoors, indicating a shift in lifestyle impacting eye health.

  • Experimental studies reveal that increased outdoor light exposure may reduce the incidence of myopia by influencing eye elongation through dopamine release in the retina.

Conclusion

• Recap of vulnerability reasons to be discussed in detail over future lectures.

• Consideration of physiological adaptive responses, such as nausea and vomiting in pregnancy, as an example of adaptive defenses against potential harm.