bio cycle 8 cooperation and conflict

what is cooperation?

a behaviour in which both the actor and the recipient benefit; it increases the actor’s inclusive fitness (directly or indirectly), not considered altruism

what is true altruism?

a behaviour that reduces the actor’s inclusive fitness while benefitting another individual, extremely rare in nature because natural selection selects against reducing your own fitness

what is selfishness?

a behaviour that increases the actor’s fitness at the expense of the recipient, ex: lion infanticide

what is spite?

a behaviour that reduces both the actor’s and the recipient’s fitness, essentially nonexistent in real populations

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

• natural 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 = focal individual’s (the person’s perspective it’s from) relatedness to the recipient

• r2 = focal individual’s relatedness to the helper (you)

• explains why relatives disagree about helping decisions

why is helping descendants not “altruism”?

because helping descendants/offspring increases inclusive fitness (your genes are passed on), 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?

their genetic interests overlap but are not identical, different individuals have different r-values so their optimal decisions differ (ex: mother wants you to help your sibling more than you want to)

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 if partner cooperates, cheating gives T > R

• if partner cheats: cheating gives P > S

• with 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 

why did group selection fail as an explanation for altruism?

one selfish individual can exploit altruistic group members → free rider problem, kin selection provides a stronger explanation

why would individuals reduce their own fitness?

to increase indirect fitness by helping relatives (kin selection) or to gain future benefits (reciprocal altruism), note: parental care is not altruism