Evolutionary theory part 2
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Evolutionary Theory Part 2. Goals for today. Kin selection and reciprocal altruism How do you assess adaptive value of a behavior? Look at some behavioral examples Introduce some models to explain primate behavior. Kin selection. A form of Natural selection

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Goals for today l.jpg
Goals for today...

  • Kin selection and reciprocal altruism

  • How do you assess adaptive value of a behavior?

  • Look at some behavioral examples

  • Introduce some models to explain primate behavior


Kin selection l.jpg
Kin selection

  • A form of Natural selection

  • Individual’s fitness is influenced by fitness of relatives (they share genes!)

Graph Strier pg 123


Behavioral choices l.jpg

Altruism-an act that benefits the helper at some cost but helps the receiver.

Selfish-acting on your own self interest to improve your fitness at cost to other’s fitness

Behavioral choices...


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How do you predict altruism?

Hamilton’s Rule

Degree of relatedness between actor and receiver

Act’s benefit to receiver’s fitness

Act’s cost to actor’s fitness

c

<

b

x

r


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Brother’s helping rear offspring.

R = .5

Benefits to helper’s fitness should be at least twice the cost.

Half brothers helping rear offspring

R = .25

Benefits to helper’s fitness should be at least four times the cost.


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Reciprocal Altruism

  • Behavior which is costly to actor but immediately benefits receiver (who is not related)- at some later time, receiver reciprocates.

  • Low dispersal rates

  • Social groups

  • Ability to discriminate between individuals

  • Time frame


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Coalitions

Hamadryas baboon

Rhesus monkey


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Chimpanzee politics

Yereon- dom. male

Nikkie- dom. male

Luit challenges,

No female support

Yereon and Nikkie

overthrow Luit

Luit and Nikkie form

Coalition, Nikkie gains

Female support

Luit- dom. Male

Nikkie

Yereon

Luit, Nikkie then

overthrow Yereon


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Criterion used to evaluate adaptation?

  • Evaluate costs and benefits

  • The compromise between these is the optimal strategy

  • How easily is this done in primatology?



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Infanticide

  • Male tenure important factor

  • Female strategies

  • Female counterstrategies


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Monogamy (pairbonding)

Males Costs

  • Mate with one female

  • Expend energy

  • defending territory

Males benefits

  • Paternal certainty

  • Exclusive access to

  • resources


Monogamy pairbonding14 l.jpg
Monogamy (pairbonding)

Female Costs

  • Limited mate choice

  • Expend energy

  • defending territory

Females benefits

  • Male care

  • Exclusive access to

  • resources


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