MODULE 18: EVOLUTION & HUMAN HEALTH

What is evolutionary medicine?

The application of evolutionary principles to understand why humans get sick, why certain diseases persist, and how traits, pathogens, and environments shape health outcomes.

Why do some harmful genetic diseases persist in populations?

Because heterozygotes may have higher fitness (e.g., sickle-cell trait and malaria), or due to mutation–selection balance and drift.

Why is cancer considered an evolutionary process?

Cancer cells accumulate mutations, undergo selection for rapid growth, and compete within the body, making tumor progression an evolutionary arms race.

What is inbreeding depression?

Reduced fitness caused by increased homozygosity of deleterious recessive alleles due to mating between relatives.

What is parent–offspring conflict?

An evolutionary conflict where offspring demand more resources than are optimal for the parent to provide, due to differing fitness interests.

Why does aging evolve?

Because natural selection weakens with age, allowing late-acting harmful mutations and favoring early-life advantages that trade off with later survival.

What are possible evolutionary explanations for fever?

Fever may be a host adaptation to inhibit pathogens, a pathogen manipulation strategy, or sometimes neutral depending on the infection.

What evidence suggests fever can be adaptive?

Experiments show that suppressing fever in some viral infections (e.g., common cold) can worsen symptoms, indicating a beneficial role.

What is lactase persistence?

The continued production of lactase into adulthood, evolved in populations with a long history of dairy farming through gene–culture coevolution.

Why is lactose intolerance common globally?

Most populations did not evolve lactase persistence because dairy was not historically consumed after weaning.

What are diseases of modernity?

Chronic conditions like heart disease, obesity, type 2 diabetes, asthma, osteoporosis, depression, and Alzheimer’s caused by mismatch between modern and ancestral environments.

Why is myopia considered a mismatch disease?

Genes predispose individuals to myopia, but modern near work (reading, screens) triggers its expression far more than in ancestral environments.

Why are breast cancer rates high in modern societies?

Modern women experience far more lifetime menstrual cycles than ancestral women, increasing estrogen exposure and elevating cancer risk.

What is the novel environment hypothesis for breast cancer?

Reproductive patterns in modern societies differ drastically from ancestral patterns, leading to higher lifetime hormonal exposure and increased cancer risk.

How do pathogens evolve?

They evolve rapidly due to large populations, short generation times, and high mutation rates, driving ongoing host–pathogen arms races.

What is antigenic drift in influenza?

The accumulation of mutations in viral hemagglutinin that allows escape from host immunity, leading to replacement of older lineages.

How does influenza evolution help vaccine prediction?

Lineages with the most non-synonymous mutations in antigenic sites are most likely to dominate in the next flu season.

How do pandemic influenza strains arise?

When different influenza strains coinfect a host, genetic reassortment produces novel combinations with new antigenic properties.

What causes antibiotic resistance evolution?

Antibiotics impose strong selection favoring resistant bacteria, which spread and may acquire compensatory mutations reducing fitness costs.

What management strategies reduce antibiotic resistance?

Use antibiotics only when needed, complete full courses, prefer narrow-spectrum drugs, maintain hygiene, and isolate resistant infections.

What is the trade-off hypothesis for virulence evolution?

Pathogens evolve virulence levels that balance host harm with transmission success; transmission mode strongly influences this balance.

When does high virulence tend to evolve?

When pathogens rely on vectors, contaminated water, or environmental persistence rather than host mobility for transmission.

What is the coincidental evolution hypothesis?

Virulence can arise as a byproduct of traits selected for in non-host environments, such as soil bacteria producing toxins.

What is the short-sighted evolution hypothesis?

Pathogens may evolve traits that increase within-host fitness but reduce transmission, as seen in poliovirus invading the nervous system.