9 - WHAT EVOLUTION DOES

Question 1

how does evolution work?

Answer 1

by tuning trade offs

Question 2

what is the optimal phenotype

Answer 2

live forever and have an infinite number of babies per second (genetic algorithms)
- id reproduction and survival weren’t involved

Question 3

why can’t be have the optimal phenotype?

Answer 3

• cost-benefit trade offs are the rule of life
• with finite resources, life must ‘choose’ (genetically) to favour one option over another
• more of one thing often means less of another

Question 4

common trade offs (6)

Answer 4

1 speed accuracy trade offs 
2 exploration-exploitation trade offs 
3 size number trade offs (bigger => fewer)
4 growth reproduction trade off
5 cost-quality trade off 
6 short-long teen trade off

Question 5

speed-accuracy trade off

Answer 5

• fast + errors
• or slow + accurate
• makes us overly sensitive to potentially threatening stimuli

Question 6

exploration-exploitation tradeoff

Answer 6

• eg exploit berry bush or explore for better

- exploitation is a type of FOCUS

Question 7

size-number trade-off

Answer 7

• eg coconut trees = few large seeds

- eg maple trees = thousands of small seeds

Question 8

growth-reproduction tradeoff

Answer 8

• reproduce a lot or help current ones grow
• eg small mustard plants reproduce a lot but don’t live long
• eg big trees grow for ages and then start seeds

Question 9

short-long term trade off

Answer 9

• intertemporal discounting
• money today or more money tomorrow
• r vs k selected species
• r = quick (fast growth and reproduction)
• k = later successionist species (slow growth and reproduction) eg tortoise

Question 10

why do we die?

Answer 10

• evolution explains (even predicts) death is an inter-temporal trade off and also why we don’t die

Question 11

what four reasons explain why we die?

Answer 11

1 disposable soma theory
2 antagonistic pleiotropy
3 mutation accumulation

Question 12

disposable soma theory

Answer 12

• extrinsic mortality weakens selection late in life
• if most part of a species die young, then selection can’t counteract kate acting deleterious mutations
• eg if 90% of wild mice die in first year (due to cold) then selection of long life genes only benefits 10% of the population
• if selection of long life genes requires resources that could keep them warmed then it’s not going to happen and be successful
• eg fruit flies in lab selected for long life (by artificially delaying reproduction) then long lived flies reproduce less - supporting disposable soma and pleiotropy theories
• lab animals still age and die as natural selection previously hasn’t had much of an impact on late life factors

Question 13

antagonistic pleiotropy

Answer 13

• good early genes can be selected even if they have bad later effects
• death is a consequence of trading off future against the present
• focusing on behaviours that support reproduction and survival early in life but at the consequence of less support for survival later in life

Question 14

what does pleiotropy mean

Answer 14

a gene can have more than one effect

Question 15

what does antagonist mean

Answer 15

the effects are working against each other
- eg risk taking in males, using resources on offspring (instead of your own longevity)
- eg semelparous species reproduce only once and often go out a massive expenditure of resources into that one reproduction - die after reproduction
^ line salmon, wheat, many ‘annual spiders’

Question 16

mutation accumulation

Answer 16

• not well supported evidence

- your cells don’t age because they suffer mutations

Question 17

hydra

Answer 17

an organism that doesn’t die or age

Question 18

henrietta lacks

Answer 18

HeLa cells do not die

• our germ line is immortal
• only our soma dies (senescence = gradual deterioration of functional characteristics)
• HeLa cell line = from a cancerous tumour she has
• 20 tonnes of these cells now exist
• leads to many medical breakthroughs

Question 19

why arent we smarter already?

Answer 19

• why don’t we have a perfect focus/infinite will power/ remember everything?
• attention focus is a trade off (too little v too much)
• ATTENTION NEEDS TO BE TUNED
• too little = don’t attend long enough / don’t start
• too much = can never change your mind or attend to alternatives (eg OCD, PTSD)
• memory should be adapted to the stability of the environment

Question 20

elman (1991) less is sometimes more

Answer 20

• a neural network designed to learn aspects of language performs better when the attention span (memory span) of the network starts off small and grows gradually
• make the memory span short to start with
• eg children only hearing parts of the sentence (eg phonemes) when learning a language
• he showed his neural network is exploration of language acquisition by providing appropriate inputs to a neural network, a network could be taught some rudiments of language acquistion

Question 21

attention being an inversed U

Answer 21

• too little attention
• optimal time spent attending
• too much attention
• too much/little = potentially pathological region

Question 22

is attention telling of being smart?

Answer 22

• things we think our smart might not be as smart as we think they are
• eg better memory

Question 23

vertical transmission

Answer 23

evolution and inheritance

Question 24

horizontal transmission

Answer 24

• culture (beliefs, social norms etc)

Question 25

what are life history trade offs?

Answer 25

• short term long term
• antagonistic pleiotropy
• size number
• growth reproduction
• others that change over lifetime

Question 26

explanations as to why we don’t have greater cognitive capacities

Answer 26

• most cognitive capacities are trade offs between too much and too little
• if our world changed less, we would probably evolve to have longer memories

Question 27

where do behaviours come from?

3

Answer 27

culture
learning (from environment - behaviourism/skinner)
evolution