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42 Cards in this Set
- Front
- Back
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Evolution of Traits
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Traits show variation--> Some trait variants are more advantageous than others-->Individuals with beneficial traits leave more offspring --> Future generations will have more individuals with beneficial traits
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How do you get the evolution of complex adaptations like behavior?
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basic social theory: B – C > 0
and Benefit is to someone else, cost is to you |
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Types of Social Interactions
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Cooperation Altruism
Selfishness Spite |
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One-time interactions
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-Non kin
-No individual recognition ex. Prisoner’s Dilemma With single interactions, the solution is always to remain silent |
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Raven example of evolution of behavior/ complex adaptation.
Why does a young raven announce that it’s found food? |
Problem for young raven:
Territorial defense by adult raven pairs Solution: Strength in numbers Find->Recruit->Success! Altruism (B1<C1) Selfish (B2>C2) B1 + B2 > C1 + C2 = SELFISH (overall benefit is to individual |
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Why relationships matter
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Cooperation can get you things that solitary efforts cannot...
Costly interactions can become beneficial with repeated interactions – reap long-term benefits As a result, you would be selected to invest in relationships (ex. Dwarf Mongoose) |
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Dwarf Mongoose example of why relationships matter
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Dominant female can stop
others breeding...but bigger groups do better, and subordinate animals can leave so powerful subordinates are allowed to breed |
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Primate sociality
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unique...
Permanent bisexual groups, stable home ranges, long-lived species, long-term relationships... The complexity of primate social lives provides many opportunity for the formation of complex social relationships |
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How do behaviors like reconciliation & cooperation evolve?
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natural selection maximizes fitness. measurable in 3 ways.
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3 ways to measure fitness
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Direct fitness
Indirect fitness Inclusive fitness |
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Direct Fitness
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An individuals direct fitness (DF) is measured by the number of their offspring that survive to reproduce
ex. mom has 3 offspring, each gets half her genes, so her fitness is 1 1/2 |
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Natural Selection (fitness through relatives)
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If natural selection operates through reproduction, then the winners are those that have the most genes in the world
Your relatives share genes with you, thus you can increase your fitness through your relatives as well |
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Determining Relatedness (r)
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fitness divided by each individual in between the 2 looking at...
ex. Coefficient of relatedness between aunt/nephew? ½ * ½* ½ = 1/8 (ma, sis, neph) |
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Indirect Fitness
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An individual’s fitness gained through relatives that pass on shared genes
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Inclusive Fitness
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An individual’s direct fitness PLUS fitness gained through relatives that pass on shared genes.
r is the probability that homologous alleles present in different individuals are “identical by descent” (ex. black tailed prairie dog giving an alarm call) |
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Inclusive fitness
ex. black tailed prairie dog giving an alarm call |
alarm calling is costly to the caller. Alarm call nepotism in black-tailed prairie dogs - more likely to call if living with kin and acquaintances)
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When Is Altruism Favored?
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An allele for an altruistic
behavior will be favored if: rB > C This is called “Hamilton’s rule” *so requires either a very high benefit or very high coefficient of relatedness |
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“Hamilton’s rule”
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An allele for an altruistic
behavior will be favored if: rB>C coefficient of relatedness, B = benefit to recipient, C= cost to helper |
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Eusociality
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Extreme form of kin selection in which few individuals in the group reproduce. Also characterized by reproductive division of labor, an overlap of generations and cooperative care of offspring born to the group
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Eusociality in Marmosets/Tamarins
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+Monogamous, polygynous or -- polyandrous
+Reproductive suppression (dominant female will surpress the reproduction in younger females behaviorally through harassment or chemically through pheromones) +Paternal and sibling care, Chimerism (always give birth to twins, twins exchange stem cells in utero) |
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Hamilton’s rule helps explain how altruism between kin could evolve, but what about helping non-kin?
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Reciprocal Altruism
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Reciprocal Altruism
Trivers’s (1971) preconditions: |
3 things needed
1) Cost to giving, benefit to receiving 2) Delay between altruistic act & reciprocated act 3) Giving is contingent upon receiving |
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Reciprocal Altruism
Requirements |
1. Individual recognition
2. Recall past interactions 3. Quantify costs & benefits 4. Recognize cheaters 5. Punish cheaters |
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Reciprocal Altruism
Example: Vampire Bats |
"I’ll barf blood, if you’ll barf blood"
60 hrs w/out blood = dead Individuals regurgitate blood, but to whom? Sharing occurred with close relatives or distant relatives with whom there was a strong association |
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Reciprocal Altruism
Why only weak evidence for reciprocal altruism? |
Required Mechanisms:
1. Individual recognition √! 2. Recall past interactions √! 3. Quantify costs & benefits ? 4. Recognize cheaters ? 5. Punish cheaters ? |
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What is a “Bond”
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greater then partly positive relationship
(can be positive or mixed. Not negative) |
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“Strong bonds”
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correlation of >2 types of interaction
(Affiliation,Time together,Coalitions,Decreased aggression) |
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Bonds in Adults
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Intersexual bonds - reproductive purposes
(Many vertebrates, mammals, birds) Intrasexual bonds - male-male or female-female, not related to reproduction (Primates, some carnivores, cetaceans. No birds, fish, reptiles, or amphibians) |
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Coalitionary Bonds
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Definition:
2 types – Coalitionary interaction = “coalition” (two indiv. help e/o out) – Coalitionary relationship = “alliance” (long-term bond) • Support in aggression • Complex interactions (competition for partners) |
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Coalitionary Bond
“Polyadic Aggressive Interaction" |
when number of individuals fight against others
*Diadic Aggression - 1 to 1 agression. If one individual cries out, then others come to help, then someone comes to support and you have 2-1 (or 3-1 or more), then you have coalition ex. |
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Coalitionary Bond
complications |
Allies are often also rivals
(Females are competitive over food, Males over females) So have to test bond ex. Capuchin Monkeys |
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Coalitionary bond - Testing
ex. Capuchin Monkeys |
(Trust games)
hand-sniffing eye-ball poking Finger in mouth |
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Stability of Bonds
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Fixed partners
-insects or birds Flexible partners (can change accord to rank etc.) requires greater cognitive abilities - must be able to understand others socially -primates or cetaceans, and humans |
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Stability of Bonds
Rank effects |
-Give support down the hierarchy
-Invest/groom up the hierarchy Result is low-ranked animals invest in alliances |
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Stability of Bonds
Flexible alliances |
-Groom down the hierarchy
-Give support up the hierarchy Competition for allies means dominants invest |
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Reconciliation
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Definition:
Increased affiliation after aggression (making up) varying styles of reconciliation – Example: macaque social styles |
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Example of style of reconciliation
macaque social styles |
Different lineages vary in terms of friendliness dependent on different grades (grades 1"weak bonds"-4"strong bonds")
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Valuable Relationship Hypothesis
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Stronger bond -> High probability of reconciliation
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Valuable Relationship Hypothesis
example chimps vs. Macaque |
Chimps:
Males = high prob. of rec Females = no rec Macaqus: Female = high prob. of rec male = no rec |
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Reconciliation results
(before and after) |
Before:
Anxiety, scratching, heart-rate, glancing After: Trust Calm Eyes shut |
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Fairness
is there a universal sense of fairness? |
test w/ monkeys show primate understanding of fairness
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Punishment
ex. Rhesus Macaques |
Consumers who punished were more likely to get food in subsequent trials
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