bio cycle 8 cooperation and conflict

what is cooperation?

a behaviour that benefits another individual and also increases the actor’s inclusive fitness (directly or indirectly)

what is true altruism?

a behaviour that reduces the actor’s inclusive fitness (direct + indirect), very rare and generally selected against

what is selfishness?

behaviour that increases the actor’s fitness at the expense of others 

what is spite?

behaviour that reduces the actor’s fitness and also reduces the recipient’s fitness, extremely rare in nature

what is direct fitness?

fitness gained through producing one’s own offspring

what is indirect fitness?

fitness gained through helping relatives reproduce, weighted by relatedness (r)

what is inclusive fitness?

direct fitness + indirect fitness

• selection acts on inclusive fitness, explaining helping behaviours toward kin

what is kin selection?

natural selection favouring helping behaviours directed at relatives, because they share alleles

• helping occurs when rb > c (Hamilton’s rule)

what is reciprocal altruism?

cooperation between non-relatives where help is given with expectation of future return

• requires repeated interactions, memory, and ability to punish cheaters

degrees of relatedness

• parent to offspring - r = 0.5

• full siblings - r = 0.5

• half-siblings - r = 0.25

• first-cousins - r = 0.125

• grandparent to grandchildren - r = 0.25

what is Hamilton’s rule?

helping behaviour is favoured when: rb > c

• r = relatedness to the recipient 

• b = benefit to recipient 

• c = cost to actor 

reformulated Hamilton’s rule (when considering different viewpoints)?

helping is favoured when: r1b > r2c

• r1 = actor’s relatedness to recipient

• r2 = actor’s relatedness to the helper (themselves or someone else’s cost)

why is helping descendants not “altruism”?

because helping offspring increases direct fitness (passing on alleles), it is cooperation, not altruism

example: should you sacrifice yourself to save 5 cousins (r=0.125) and 2 half siblings (r=0.25)?

calculate rb:

• (5 × 0.125) + (2 × 0.25) = 1.125 > 1 life cost → yes, kin selection favours sacrifice 

example: should a bird help parents raise 4 full siblings or reproduce itself, producing 3 offspring?

• helping siblings: rb = 0.5 × 4 = 2

• reproducing: rb = 0.5 × 3 = 1.5

• help siblings (higher inclusive fitness)

helping half-sister increases her fitness by 20 units. Mother’s POV: max cost you should pay?

• mother’s relatedness to both of you = 0.5

• her rule = 0.5(20) > 0.5c → 10 > c

• c < 10

• correct answer: c. help only if c < 10 units

father’s POV with the same problem?

• father only shares genes with you, not your half sister

• so r2 > r1 → no benefit 

• correct answer: no nonzero cost is acceptable 

stepfather’s POV?

• he shares no genes with either child, so he is indifferent

• correct: always acceptable (no genetic cost/benefit)

why is there conflict even among close relatives?

genetic interests overlap but are not identical (ex: siblings value their own reproduction more than a sibling’s)

how do asymmetries in relatedness generate conflict?

if relatives differ in r-value to each other and to themselves, optimal decisions for one relative may differ from optimal decisions for another

what game model explains cooperation vs cheating between non-relatives?

the prisoner’s dilemma, where typical payoffs

T > R > P > S

• T = temptation to cheat

• R = reward for mutual cooperation

• P = punishment for mutual cheating

• S = sucker’s payoff (you cooperate, partner cheats)

why is cheating the “rational” one-shot choice?

• because T > R and P > S

• no future consequences → cheating maximizes fitness

under what conditions can cooperation evolve among unrelated individuals?

when interactions are repeated and individuals can: 

• recognize patners

• remember past behaviour

• reward helpers

• punish/avoid cheaters

• found in wolves, chimps, humans 

why are “social emotions” useful in evolution?

emotions like guilt, trust, resentment maintain social scorekeeping, promoting cooperation and detering cheating