Lecture 19 Flashcards
1
Q
Evolutionary Medicine
A
- Application of evolutionary principles to problems in health and disease
- Ask why rather than how
- Better understanding = better prevention, treatment
- Diseases need both proximate explanations of underlying mechanisms as well as ultimate explanations of why any vulnerabilities exist
2
Q
Questions in evolutionary medicine
A
- Why are we vulnerable to disease
- Why do we age
- Which symptoms of disease are harmful and which are helpful
- When do we expect drug resistance to evolve
- Will vaccines lead to evolution of pathogens
- How virulent should we expect novel pathogens to be and how will they evolve over time
3
Q
Five reasons why we are vulnerable to disease
A
- Tradeoffs
- Natural selection acts to increase reproductive success of genes, not health
- Some signs of disease are actually defenses
- Mismatch with current environments
- Pathogens are evolving
4
Q
Tradeoffs
A
- Structures and systems must balance conflicting demands
- DNA Repair: Increase longevity, low fecundity
- Immune defense: targets pathogens, might target itself(immunopathology)
5
Q
Natural selection acts to increase the reproductive success of genes, not health
A
- Some health issues may be decoupled from fitness
6
Q
Some signs of disease are actually defenses
A
- If it is adaptive for parasites, then test. If adaptive for host, don’t test
7
Q
Mismatch with current environments
A
- Our environment has changed at rate that exceeds our rate of evolution
- Past environment: trait was beneficial in past environment, so increase frequency for that trait -> current environment: trait leads to vulnerability to disease
8
Q
Pathogen evolution
A
- Pathogens evolve much more quickly than we do
- Fast generation times
- Large population sizes
- High mutation rates
9
Q
Some signs of disease may be defenses
A
- ## Quantify costs and benefits of trait to both individual and pathogens
9
Q
Fever
A
- Elevated body temperature is a common response to pathogen infection
- Typical treatment is to take aspirin, acetaminophen, or ibuprofen
- Evolutionary medicine asks: why do we have a fever
10
Q
Evolutionary perspective on why we have fevers
A
- Fever is a direct effect of pathogen replication in a host. Pathogen success increases with fever. Disease mechanism
- Fever is an adaptive defense against pathogens. Pathogen success decreases with fever. Defense mechanism
11
Q
Behavioral thermal regulation in iguanas
A
- Iguanas are ectotherms, and therefore behaviorally regulate body temperature
- Iguanas injected with live bacteria tend to bask and elevate their body temperatures
12
Q
Adaptive value of fever
A
- Iguanas infected with a bacterial pathogen were held at a series of temperatures and prevented from behaviorally regulating
- Preferred body temperature is 38-39 for these iguanas
- Iguanas held at fever level temperatures tended to live longer
13
Q
Fever may increase efficacy of immunity
A
- Differences in iguana survival are not simply an effect of temperature on growth rate of pathogen
- Increase temp, decrease doubling time
14
Q
What about fever in humans
A
- Can’t easily experimentally regulate body temperature in humans
- Experimentally induce a mild infection and test for effectiveness of anti-fever treatment
- Symptoms were worse in individuals given medicine that reduces fever
15
Q
Adaptive value of fever in humans
A
- Immune response is suppressed in individuals given anti-fever drugs
- Evidence to suggest that fevers are part of an evolved defense system -> treating them might not always be helpful??
16
Q
Mismatch to current environments
A
- Humans may be adapted to a different environment and lifestyle than current one
- Can account for some diseases
17
Q
Myopia
A
- Near-sightedness: distant objects are out of focus, caused by elongated eye
- Varies in frequency across populations
- Frequency has been increasing
- Sunlight cause increase dopamine -> decrease in elongation -> reduce myopia
18
Q
Evidence of genetic basis for myopia
A
- ## Heritability of myopia has been estimated many times
19
Q
GxE interaction
A
- Possibility that genes that give rise to myopia now did not cause myopia in past environments
- Modern lifestyle includes much more reading under artificial light during development, less time outdoors
- Need sunlight
20
Q
Comparative study for myopia
A
- Researchers study population with recent shift in lifestyle
- 506 individuals got eye exam
- Myopia would be more frequent in younger age groups because they grew up in a modern environment with artificial light and less time outdoors
