the evolution of cooperation. i. issue - how can cooperation evolve, especially if by cooperating,...

The Evolution of Cooperation


I. Issue

- How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another?


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- However, cooperation is OBSERVED and necessary:


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among genes in a genome


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among organelles in a cell


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among cells in a multicellular organism


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among organisms in a social group


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among organisms in a social group

between species in symbiotic relationships


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II. Mechanisms (Nowak, 2006, Science).

A. Kin Selection (Hamilton, 1964)

A. Kin Selectionr > c/b

White-fronted bee-eaters

Nowak, M. A. 2006. Five rules for the evolution of cooperation. Science 314:1560-1563.


I. Issue


A. Kin Selection (W. D. Hamilton)

B. Direct Reciprocity (Trivers 1971)

http://www.sciencemag.org/content/vol314/issue5805/images/large/314_1560_F3.jpeg


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- prisoners dilemma

B Stays Silent B Betrays

A Stays Silent both get 6 months A gets 10 years; B goes free

A Betrays B gets 10 years; A goes free

both get 2 years


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- prisoners dilemma So, cooperation pays...but blind sacrifice does not!




both get 2 years


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- in the "repeated prisoner's dilemma":




both get 2 years


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- it's adaptive to cooperate if there are repeated interactions with the same partner




both get 2 years


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- it works by 'tit for tat' or 'hold if it pays' (if you start on cooperate)




both get 2 years


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- it works by 'tit for tat' or 'hold if it pays' (if you start on cooperate)




both get 2 years

- cooperation can evolve only if w > c/b .... if the frequency of encounter exceeds the cost/benefit ratio of the altruistic act. If this is the case, you may profit in the future if the act is reciprocated (and if w is high, then there is good chance it will be)


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- Mutualisms: both partners have increased fitness, relative to other members of their species, by interacting with another species.


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- Positive feedback can enhance the dependency between partners


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- Positive feedback can enhance the dependancy between partners

Atta cephalotes, the "leaf cutter" ants, farm and eat a species of fungus that lives nowhere else now.

Acacia and Acacia ants

Corals and zooxanthellae

Gleaners

Aphid farming by antsFrugivory

PollinationProtozoans in Termites


“watcher”




C. Indirect Reciprocity – “reputation”



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C. Indirect Reciprocity (Nowak 1998)

- In large populations (humans), the frequency of encounter may be low, and the relationship is asymmetric (one person CAN help, the other may never be able to).


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- Helping establishes a good reputation; and increases the chance that others (not the direct beneficiaries) will help us if we need it.


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- Helping establishes a good reputation; and increases the chance that others (not the direct beneficiaries) will help us if we need it.

- People who are observed to be more helpful are more likely to be helped.

- Even in other species... Bshry 2006 - Cleaner Wrasse

- wrasse eat parasites off "client" fish... but they can cheat and eat mucous, which is bad for the client fish.



- Client fish observe wrasses, and prefer the wrasses that don't cheat




- AND, when WATCHED, wrasses cheat less and cooperate more...




- AND, when WATCHED, wrasses cheat less and cooperate more...

- so wrasses cooperate with current clients to gain favor (reputation) with others that are observing.

- cooperation can only evolve IF q > c/b, where:

q = prob. of knowing someone's reputation



D. Network Reciprocity

http://www.youtube.com/watch?v=frpp6DjCaJU

http://www.youtube.com/watch?v=frpp6DjCaJU




D. Network Reciprocity

E. Group Selection

E. Group Selection


Pseudomonas flourescens

Colonies with high concentration of mat-builders (expensive proteins) float; if cheaters increase in number, colony sinks and dies.

E. Group Selection

“givers and takers” andEvolutionarily Stable Strategies

Scenario 1: Payoff to hawks is always greater than payoff to doves, regardless of density. Even though all doves is better for the group, it is not an ESS… it can be ‘invaded’ by hawks.

All hawks IS an ESS, though, because doves always at disadvantage and can’t increase in population.

c

Scenario 2:Here, the cost of competition among hawks is high, so as hawk density increases, payoff to hawks decline rapidly. A population of all hawks is not an ESS now – it can be invade by doves. There is a stable equilibrium in which hawks and doves are maintained in the population.

E. Group Selection

“givers and takers” andEvolutionarily Stable Strategies


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Conclusions

- cooperation can evolve as a result of selection; even among unrelated entities (symbioses)

- when cooperation occurs at one level, it creates a new level of organization... cells cooperate and ORGANISMS are produced... organisms cooperate and SOCIAL UNITS are produced.

- Cooperation allows specialization, and creates diversity at several levels

Vogel, G. 2004. Evolution of the golden rule. Science 303:1128-1131.

Game:

Give one monkey a pebble. If it gives it back (co-operation), it gets a cucumber slice.


Game:

Give one monkey a pebble. If it gives it back (co-operation), it gets a cucumber slice.

Repeat with a second monkey, in view of the first, but give the second monkey a grape (better reward).

GRAPE?… what the $%#@@!!


Fair trade. Capuchin monkeys refuse to cooperate when they see a comrade receive a better reward for the same task.

Game:

Give one monkey a pebble. If it gives it back (co-operation), it gets a cucumber.

Repeat with a second monkey, in view of the first, but give the second monkey a grape (better reward).

First monkey will no longer return the pebble for a cucumber.

KEEP your #$#@ CUCUMBER!!

Chimps helping strangers - http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0050184

• 36 wild-born chimps (orphaned) – Uganda• Two novel experimenters struggle over stick, thrown in cage• Experimenter reaches for stick• Does chimp help and get the stick in 60 sec? How about a child?

Chimp

Child

http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050184

http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050184

Chimps helping strangers - http://www.livescience.com/animals/070625_chimp_altruism.html

yes, as often as 18 month old children if the experimenter reaches for it.


Still, humans at the sanctuary provide the chimpanzees food and shelter, so helping people out could simply be in their best interests.


9 unrelated chimps ‘trained’ to use a mechanism in a pre-test. They remove the peg, and then can walk around the corner, through the newly opened port, and get the food.

• Both the target and the distracter door were held shut by chains. • subject (S) could release the chain of the target door. • In the experimental condition, food was placed in the target room (subject could help) by releasing the target chain. In the control condition, food was placed in the distracter room, so that the recipient would try to open the distracter door. In this situation, it was irrelevant (with respect to the recipient's attempt to open the distracter door) whether the subject released the target chain. The target measure in both conditions was whether the subject released the target chain. (from Warneken, PLOS 2007). • 3 acted as recipients and 6 as subjects – 10 trials for each pairing; 5 experimental and 5 controls (banana in ‘distractor’ room).

Chimp helping chimp

Mean percentage of trials with target behavior (releasing the target chain) by condition. Error bars represent SEM. Each subject was tested in both conditions in a within-subject comparison. (Warneken, PLOS 2007).

Subjects pull bar for recipient to access food significantly more often than the control (p < 0.025). Difference increased over trials.

The Evolution of CooperationConflicts within Families

Parent’s potential for future reproduction may favor them investing in survival rather than parental care.


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III. Conflicts

A. Parent vs. Offspring

D. Conflicts within Families2. Parent - offspring

Selection can favor parents that abort care of current offspring to improve survival and future reproductive success…


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III. Conflicts

A. Parent vs. Offspring

B. Parent-Parent

IGFII gene – stimulates growth

On in males, stimulating the growth of their own offspring; off in females, as she bears the cost of growing embryos and all are hers.

B. Parent-Parent

IGFII inhibitor gene – slows growth

Off in males, stimulating the growth of their own offspring; on in females, as she bears the cost of growing embryos and all are hers.

C. Sibling - sibling

B. Sibling - sibling

Conflicts....

I. Among Relatives

II. Among Non-Relatives

A. Interspecific Competition

Conflicts....

I. Among Relatives



- within both populations, those that are competing within AND between species are at an energetic and reproductive disadvantage.

Conflicts....

I. Among Relatives




- competititive exclusion

Conflicts....

I. Among Relatives





- niche partitioning

Conflicts....

I. Among Relatives





- niche partitioning; character displacement

Both species benefit by reducing the interaction; once it is reduced, there is no benefit to reestablish the interaction.

the evolution of cooperation. i. issue - how can cooperation evolve, especially if by cooperating,...

Documents

evolution of cooperation

genome slide

cell slide

immediate fitness

multicellular organism

social group slide

mechanisms nowak

years b