UNIT 3 DAY 1 - DARWINIAN MEDICINE

Question 1

key themes from chapter 1

Answer 1

• the body has good and a bad design
• good: eyes (precision and can see well)
• bad: spine (not designed well, prone to injury), food tube near wind pipe

Question 2

2 causes of disease

Answer 2

proximate and evolutionary

Question 3

proximate explanation

Answer 3

• “near” or direct causes –> a specific gene or behaviour that leads to a disease
• “what” or “how” questions

Question 4

evolutionary explanation

Answer 4

• why are we designed the way that we are allow this disease to happen
• “why questions”
• neglected in medicine, focuses on direct, structural causes for disease
• entails looking for possible benefits of aversive experiences
• is attainable scientifically with careful research

Question 5

causes of disease = defenses

Answer 5

• defenses vs defects
• one harmful to eliminate another one beneficial

Question 6

cause of disease = infection

Answer 6

• opponents that are also evolving to overcome defenses

Question 7

causes of disease = novel environments

Answer 7

• provide stimuli that our bodies don’t know how to react to (pollution, fatty acids)

Question 8

causes of disease = genes

Answer 8

• some now undesirable genes weren’t harmful when humans existed in more of a natural environment –> genes that cause harm may be beneficial in other ways –> mutations, though often eliminated, can cause disease at individual levels

Question 9

causes of disease = design compromises

Answer 9

• many of the body’s apparent design flaws aren’t mistakes just compromises

Question 10

causes of disease = evolutionary legacies

Answer 10

• eg. food tube near wind pipe not ideal but too late to change it now

Question 11

eugenics

Answer 11

• changes genes to produce the most desirable traits

Question 12

social darwinism

Answer 12

• applying natural selection concepts to sociology, economics and politics
• “imperialism justified by nature”
• justifying leaving people behind via natural selection

Question 13

why don’t the authors approve of either eugenics or social darwinism?

Answer 13

• don’t want to help natural selection improve the human species
• goal of medicine is to help the sick people, not species

Question 14

if we were to improve species what would that entail?

Answer 14

• sterilisation of certain groups in order to improve the species/race

Question 15

What does natural selection have to do with getting sick?

Answer 15

• natural selection occurs whenever genetically influenced variation among individuals affect their survival and reproduction
• genetic mutations that increase vulnerability to infection will never become common but genes that cause resistance to infection are likely to spread in the gene pool if all works out

Question 16

Herbert Spencer: “Survival of the fittest” misleading

Answer 16

• survival: measured by the reproduction
• survival increases fitness only so far as it increase the later population
• fittest: best suited to the particular environment the species inhabitants
• not necessarily the healthiest, strongest or fastest

Question 17

Why is evolution by natural selection not seen as proceeding according to plan or in a predictable way?

Answer 17

• in a real world chance has a large role in outcomes
• new variations arise, by mutations (large chance events)
• genetic drift will be an important force when variants are rare or small populations
• favourable variance depends on environment at that time

Question 18

What are quantitative traits and how do they involve natural selection?

Answer 18

• natural selection is very effective at shaping quantitative traits
• quantitative traits are traits that can be measured
• finches evolves through many small steps causing well adapted quantitative traits
• maintains close to ideal size for local environment but not perfect

Question 19

evolutionary hypotheses

Answer 19

• tested scientifically –> functionality of organs
• leads to new discoveries

Question 20

adaptationist approach

Answer 20

• studies of the functional reasons for human attributes are based on a method of investigation
• the investigation can confirm if these attributes are either there or not
• if they are there, there may be of medical significance

Question 21

how do beavers various features contribute to fitness?

Answer 21

• harvest trees in or near their ponds for their food and shelters
• use their teeth to chop through the trunks near the ground, drag the trees to the water and tow them into their lodges

Question 22

how do beavers decide which trees to watch?

Answer 22

• do it adaptively: make a rational decision
• range in sizes of trees harvested by beavers would steadily decrease as the distance from the pond increases, beavers take trees closer to the pond

Question 23

how do clutch of eggs (songbirds) various features contribute to fitness

Answer 23

• she and her mate lay a clutch of eggs
• her reproductive success for this breeding season will depend entirely on those eggs
• she is not trying to assure survival of the species, she is trying to maximise her own lifetime reproductive success
• laying too many would decrease her total lifetime reproduction because not enough food and chicks die or her health is jeopardised due to caring for too many
• David Lack: birds adjust the number of eggs they lay to maximise their individual reproductive success

Question 24

How do sex ratio various features contribute to fitness?

Answer 24

• important strategies in maximises fitness: producing offspring of whatever sex is in short supply, minority sex has mating advantages
• producing male offspring when females are scarce will be selected against because many of those males will never have offspring
• producing females if males are scarce, individuals that produce females will not have as many grad-offspring as individuals who produce males
• there needs to be a balance in ratio of male to female

Question 25

Why do gene pool and natural selection do more good than harm?

Answer 25

• easier to use than having to describe them literately

Question 26

fever

Answer 26

• an adaptation shaped by natural selection specifically to fight infection
• defense against infection

Question 27

why don’t we have fevers all the time to prevent infections from starting?

Answer 27

• depletes nutrient reserves 20% faster
• causes temporary male sterility, tissue damage etc
• no regulation process is perfect so sometime fevers may rise too much and other not enough

Question 28

what is iron withholding?

Answer 28

• defense
• egg whites were used prior to antibiotics
• free iron in blood increases infection risks; iron makes pathogens stronger so we withhold it from bacteria

Question 29

transferrin

Answer 29

• protein that binds iron tightly
• release iron only to cells that carry special recognition markers
• bacteria don’t have the “code” to get in
• in presence of infection body realises leukocyte endogenous mediator which raises body temperature and decreases the availability of iron in the blood

Question 30

how is an itch that drives you crazy seen as a defence?

Answer 30

• the itching is our adaptation to avoid future botes
• best defense against infection is to avoid pathogens

Question 31

how is strench of vomit seen as a defense?

Answer 31

• distress of nause discourages us from eating more of the noxious substance, and its memory discourages future sampling of whatever caused it

Question 32

how is pain of heat, cold and injuries seen as a defense?

Answer 32

• continued pain from infection or injury is adaptive because continued use of damaged tissue may compromise the effectiveness of other adaptations, such as tissue reconstruction and antibody attacks on bacteria
• pain motivates us to escape quickly when are bodies are being damaged, and the memory of the pain teaches us to avoid that situation

Question 33

how is the illness that makes you achy and tired seen as a defense?

Answer 33

• aches and tiredness encourages inactivity
• inactivity favours the effectiveness of immunological defenses and repair of damaged tissues

Question 34

how is diarrhea seen as a defense?

Answer 34

• diarrhea is a defense that helps flush out sickening bacteria
• but may want to stop diarrhea is blocking its defence

Question 35

how is menstruation seen as a defence?

Answer 35

• effective defense against uterine infection
• shredding of uterine lining and menstrual blood are more effective in destroying pathogens while minimising losses of nutrients

Question 36

pathogens adaptations

Answer 36

• evasion of host defenses (trypanosomes, HIV)
• attack on host defenses (HIV)
• pathogen dispersal (malaria)
• host manipulation (rabies, cholera)
  –> some are byproducts of quest for nutrients not actual adaptations

Question 37

why evolutionary training should be central to medical education

Answer 37

• benefits approach to disease
• ideas are simple, easy to apply

Question 38

fitness

Answer 38

number of grandchildren a organism produced

Question 39

adaptationist program

Answer 39

• assumes that every feature on an organism may be adaptive, so one can pose and test hypotheses about how each is adaptive