The Evolution of Cooperation

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?

I. Issue - How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another? - However, cooperation is OBSERVED and necessary:

I. Issue - How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another? - However, cooperation is OBSERVED and necessary: among genes in a genome

I. Issue - How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another? - However, cooperation is OBSERVED and necessary: among genes in a genome among organelles in a cell

I. Issue - How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another? - However, cooperation is OBSERVED and necessary: among genes in a genome among organelles in a cell among cells in a multicellular organism

I. Issue - How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another? - However, cooperation is OBSERVED and necessary: among genes in a genome among organelles in a cell among cells in a multicellular organism among organisms in a social group

I. Issue - How can cooperation evolve, especially if by cooperating, an entity reduces its own immediate fitness in sacrifice to that of another? - However, cooperation is OBSERVED and necessary: among genes in a genome among organelles in a cell among cells in a multicellular organism among organisms in a social group between species in symbiotic relationships

I. Issue II. Mechanisms (Nowak, 2006, Science).

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton)

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) - r > c/b

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) - r > c/b - Coefficient of relatedness must exceed the cost/benefit ratio of the act.

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) - r > c/b - Coefficient of relatedness must exceed the cost/benefit ratio of the act. - So, dieing while saving three sibs (c/b = 1/3) is adaptive because the coefficient between sibs is 1/2 (> 1/3).

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971)

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - 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

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - prisoners dilemma So, cooperation pays...but blind sacrifice does not! 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

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - in the "repeated prisoner's 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

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - in the "repeated prisoner's dilemma": - it's adaptive to cooperate if there are repeated interactions with the same partner 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

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - in the "repeated prisoner's dilemma": - it's adaptive to cooperate if there are repeated interactions with the same partner - it works by 'tit for tat' or 'hold if it pays' (if you start on cooperate) 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

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - in the "repeated prisoner's dilemma": - it's adaptive to cooperate if there are repeated interactions with the same partner - it works by 'tit for tat' or 'hold if it pays' (if you start on cooperate) 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 - 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)

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - Mutualisms: both partners have increased fitness, relative to other members of their species, by interacting with another species.

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - Mutualisms: both partners have increased fitness, relative to other members of their species, by interacting with another species. - Positive feedback can enhance the dependancy between partners

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) - Mutualisms: both partners have increased fitness, relative to other members of their species, by interacting with another species. - 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
Aphid farming by ants Frugivory Gleaners Pollination Protozoans in Termites

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) C. Indirect Reciprocity (Nowak 1998)

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) 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).

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) 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). - Helping establishes a good reputation; and increases the chance that others (not the direct beneficiaries) will help us if we need it.

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) 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). - 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.

I. Issue II. Mechanisms (Nowak, 2006, Science). A. Kin Selection (W. D. Hamilton) B. Direct Reciprocity (Trivers 1971) C. Indirect Reciprocity (Nowak 1998) - But 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). - 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 Cleaner Wrasse

- 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.

- 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

- 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...

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

- 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... - 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

I. Issue II. Mechanisms (Nowak, 2006, Science). III. Conclusions

I. Issue II. Mechanisms (Nowak, 2006, Science). III. Conclusions - cooperation can evolve as a result of selection; even among unrelated entities (symbioses)

I. Issue II. Mechanisms (Nowak, 2006, Science). III. 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.

I. Issue II. Mechanisms (Nowak, 2006, Science). III. 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

Conflicts.... I. Among Relatives

Conflicts.... I. Among Relatives A. Parent Conflicts

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants ALL her offspring to survive and so does NOT want one to grow disproportionately.

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants all offspring to survive and so does NOT want one to grow disproportionately. - Insulin-like Growth Factor II:

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants all offspring to survive and so does NOT want one to grow disproportionately. - Insulin-like Growth Factor II: - stimulates growth of embryo.

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants all offspring to survive and so does NOT want one to grow disproportionately. - Insulin-like Growth Factor II and gene imprinting: - stimulates growth of embryo. - gene from male is ON; gene from female is OFF

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants all offspring to survive and so does NOT want one to grow disproportionately. - Insulin-like Growth Factor II: - stimulates growth of embryo. - gene from male is ON; gene from female is OFF - Also, there is an inhibitor to IGF-II

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants all offspring to survive and so does NOT want one to grow disproportionately. - Insulin-like Growth Factor II: - stimulates growth of embryo. - gene from male is ON; gene from female is OFF - Also, there is an inhibitor to IGF-II - gene from male is OFF, gene from female is ON.

Conflicts.... I. Among Relatives A. Parent Conflicts - male parent (especially in multiply inseminated species) wants OWN offspring to receive resources and grow large - female parent, nourishing many embryos, wants all offspring to survive and so does NOT want one to grow disproportionately. - Insulin-like Growth Factor II: - stimulates growth of embryo. - gene from male is ON; gene from female is OFF - Also, there is an inhibitor to IGF-II - gene from male is OFF, gene from female is ON. - Infanticide by adoptive parents ... male lions kill cubs and bring female into estrus

Conflicts.... I. Among Relatives A. Parent Conflicts - Red Deer - In poor years, small doe's selectively abort male embryos at a higher frequency than female embryos. (In a harem forming species, males are unlikely to mate; especially if they are small).

Conflicts.... I. Among Relatives A. Parent Conflicts - Red Deer - In poor years, small doe's selectively abort male embryos at a higher frequency than female embryos. (In a harem forming species, males are unlikely to mate; especially if they are small). - But males with high breeding success (probability of mating, fertility, and proportion of normal sperm) can influence sex ratios also; they produce more sons. (Gomendio et al., Science )

Conflicts.... I. Among Relatives A. Parent Conflicts - Red Deer - In poor years, small doe's selectively abort male embryos at a higher frequency than female embryos. (In a harem forming species, males are unlikely to mate; especially if they are small). - But males with high breeding success (probability of mating, fertility, and proportion of normal sperm) can influence sex ratios also; they produce more sons. (Gomendio et al., Science ) - So, in this system, females often maximize production of daughters, while males maximize production of sons.

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts - Parents are concerned with their cumulative fitness; including potential future fitness... not the survival of each and every offspring.

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts - Parents are concerned with their cumulative fitness; including potential future fitness... not the survival of each and every offspring. - Obviously, each offspring is concerned with THEIR OWN survival

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts - Parents are concerned with their cumulative fitness; including potential future fitness... not the survival of each and every offspring. - Obviously, each offspring is concerned with THEIR OWN survival - Birds often lay more eggs than they can care for, on average. If it is a good year, they can take advantage and raise more chicks. If it is a poor or average year, the last chick to hatch will die.

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts - Parents are concerned with their cumulative fitness; including potential future fitness... not the survival of each and every offspring. - Obviously, each offspring is concerned with THEIR OWN survival - Birds often lay more eggs than they can care for, on average. If it is a good year, they can take advantage. If it is a poor or average year, the last chick to hatch ends up dieing. - Red Deer: in poor years, small doe's selectively abort male embryos at a higher frequency than female embryos. (In a harem forming species, males are unlikely to mate; especially if they are small).

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts C. Sibling Conflicts

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts C. Sibling Conflicts - siblicide occurs where resources are limiting, or social dominance is a priority.

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts C. Sibling Conflicts - siblicide occurs where resources are limiting, or social dominance is a priority. - Cattle Egrets ...lay three eggs; first two have high androgens. If food is limiting, they will kill the third chick

Conflicts.... I. Among Relatives A. Parent Conflicts B. Parent-Offspring Conflicts C. Sibling Conflicts - siblicide occurs where resources are limiting, or social dominance is a priority. - Cattle Egrets ...lay three eggs; first two have high androgens. If food is limiting, they will kill the third chick - Hyenas... same sex siblicide more common than female-male; matriarchal society

Conflicts.... I. Among Relatives II. Among Non-Relatives A. Interspecific Competition

Conflicts.... I. Among Relatives II. Among Non-Relatives A. Interspecific Competition - within both populations, those that are competing within AND between species are at an energetic and reproductive disadvantage.

Conflicts.... I. Among Relatives II. Among Non-Relatives A. Interspecific Competition - within both populations, those that are competing within AND between species are at an energetic and reproductive disadvantage competititive exclusion

Conflicts.... I. Among Relatives II. Among Non-Relatives A. Interspecific Competition - within both populations, those that are competing within AND between species are at an energetic and reproductive disadvantage competititive exclusion - niche partitioning

Conflicts.... I. Among Relatives II. Among Non-Relatives A. Interspecific Competition - within both populations, those that are competing within AND between species are at an energetic and reproductive disadvantage. - competititive exclusion - niche partitioning; character displacement Both species benefit by reducing the interaction; once it is reduced, there is no benefit to reestablish the interaction.

Life History Evolution
I. Components of Fitness and Trade-Offs A. Components

I. Components of Fitness and Trade-Offs A. Components 1. probability of survival

I. Components of Fitness and Trade-Offs A. Components 1. probability of survival 2. number of offspring

I. Components of Fitness and Trade-Offs A. Components 1. probability of survival 2. number of offspring 3. quality of offspring (probability of their survival)

BASAL METABOLISM GROWTH REPRODUCTION B. Trade-Offs
1. survival and growth vs. reproduction: 'r' vs. 'K' strategists BASAL METABOLISM "K"OMPETITIVE ABILITY GROWTH REPRODUCTION "r"

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history - When all else is equal, reproducing early and often is adaptive; even if it kills you. The faster you create copies that can copy themselves, the more the "compounding interest" effect of exponential reproduction can get working for you. Aphid "stem mother" produces live offspring asexually...

- But if that's true, why are there perennials?
Because environment matters. Lots of small offspring means that they only survive in a benign environment. But some environments are not benign... so the only way to reproduce successfully is to produce larger offspring... which may require longer survival to accumulate resources to make large offspring.

- But if that's true, why are there perennials?
Because environment matters. Lots of small offspring means that they only survive in a benign environment. But some environments are not benign... so the only way to reproduce successfully is to produce larger offspring... which may require longer survival to accumulate resources to make large offspring. - Or, as a consequence of storing energy, you may be able to reproduce disproportionately more later and 'recoup' the losses of delaying reproduction. 1 2 3 4 Annual 100 10,000 1,000,000 Perennial (Redwood) 1,000,001 each year

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history C Evidence of Trade-Offs 1. Fruit flies - delay reproduction and extend their lifespan

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history C Evidence of Trade-Offs 1. Fruit flies - delay reproduction and extend their lifespan 2. Blue tits - more chicks, shorter lifespans

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history C Evidence of Trade-Offs 1. Fruit flies - delay reproduction and extend their lifespan 2. Blue tits (birds) - more chicks, shorter lifespans 3. Crickets - short-winged morphs (decreased survival and less growth energy) have larger eggs; long-winged forms have smaller eggs

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history C Evidence of Trade-Offs 1. Fruit flies - delay reproduction and extend their lifespan 2. Blue tits (birds) - more chicks, shorter lifespans 3. Crickets - short-winged morphs (decreased survival) have larger eggs; long-winged forms have smaller eggs 4. Trade-offs between offspring size and number within species size number

B. Trade-Offs 1. survival and growth vs. reproduction: 'r' vs. 'K' strategists 2. # vs. quality of offspring lots of little or a few big 3. Timing: annual vs. perennial life history C Evidence of Trade-Offs 1. Fruit flies - delay reproduction and extend their lifespan 2. Blue tits (birds) - more chicks, shorter lifespans 3. Crickets - short-winged morphs (decreased survival) have larger eggs; long-winged forms have smaller eggs 4. Trade-offs between offspring size and number within species 5. Is there an optimal offspring size? - Probably a balance between selection on offspring survival (large size) and parental fitness (increased number). - Benign env... maximize number - Harsh env... maximize size

The Evolution of Cooperation

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