BIOL 3010 Lecture Notes - Lecture 4: Pleistocene, Statistical Significance, Natural Selection

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1 Dec 2014
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Lecture 4 Sept.
12/14
Adaptationism and Life History Theory
- Need criteria to distinguish which traits are adaptation
- Lag : environments change faster than gene frequencies
- Natural selection acts on phenotype
- If environment changes you’d end up with phenotypes that would be adaptive in
previous environment
EEA
- Entire set of environment regularities that were relevant to human evolution
- Pleistocene is shortcut answer, this is the period where humans actively evolved
- A lot of human traits such as eyesight and movement were there before Pleistocene
- Example: EEA for vision in fish: statistical significance of physical features: light moving
through water vs. through air
- Our present social adaptations assume social conditions of past
- The good definition of EEA is specific to adaptation
- What is the environment that made this species different than others?
Was foraging in open maladaptive for a rabbit?
- Have to evaluate decision role rather than the outcome
- How to evaluate whether decision was adaptive or not:
Signal Detection Theory:
- Rabbit could go in open or brush
- More food in the open but also more predators, safer in brush but less food
- Rabbit has to decide to act whether predator is there or absent.
Predator is actually…
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Present Absent
Rabbit thinks
predator is…
Present HIT
(avoided getting eaten)
False Alarm
(misses out on food)
Absent Miss
(Gets eaten)
Correct Rejection
(Rabbit gets food)
- Miss is the worst outcome
- There are two errors: miss and false alarm
- The more cues, the more certain you are that a predator is there
- High frequency of cues and low # of cues means fairly certain predator is absent
- High frequency of cues with high number of cues means certain that predator is present
- Errors are inevitable in decision making
- Want to look at benefits of answer
- It was maladaptive because the rabbit was eaten, but it may have been an adaptive
decision if he was going to starve to death in an hour (had to go into open to survive)
Life History Theory: What are Lifetimes for?
- Lifetimes are finite
- 2 kinds of effort which trade off against each other.
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Somatic Effort: building and maintaining a body
Building, gathering resources, making friendships etc.
Reproductive effort: mating, redistributing resources
- Natural selection creates organisms which are good at replicating
- Very early in life all effort is somatic effort
- By pre teens there is a little bit of reproductive effort in the sense of taking care of
younger family members. Want genes to carry on
- Early adulthood  mating effort
- Shortly after is parenting effort
- Purpose of somatic effort is to build body that will be good at reproduction
Lecture 5 Sept.
15/14
Life History Theory and Game Theory
What are lifetimes for?
Life history: standard developmental sequences an organism goes through
- Lifetimes are about reproduction
- Level of gene
- Point of life is for reproduction
- Somatic effort and reproductive effort
- Somatic is devoted to increasing reproductive value
-Reproductive Value: expected lifetime residual reproductive output
- RV increases until adulthood point where physically capable to have kids then slowly
declines
- Early in life 100% of effort is somatic (anything that increases reproductive value)
- There is a trade-off between efforts (somatic and reproductive)
Why don’t we live forever?
- Williams’ pleiotrophy: genes have multiple effects
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