Evolution Social Behavior Flashcards
Altruism
an act that benefits other at one’s own cost
Cooperation is an Action that Benefits:
1) both a recipient and the actor or
2) provides a benefit to another individual (recipient) but not to the actor (altruism)
Selfish
benefits the actor and costly to recipient
Mutualistic
beneficial to both
Spiteful
costly to both
Group Selection
- one popular mechanism to explain the evolution of selflessness/altruism
- applies Darwin’s postulates to groups
Why Group Selection Doesn’t Work
selection acts on individuals not groups
group selection cannot explain evolution of altruistic behaviors
How Does Altruism Evolve?
kin selection
Kin Selection
when individuals interact selectively with relatives
process whereby natural selection favours a trait due to its positive effects on the reproductive success of an organism’s relatives
Hamilton’s Rule
asserts that a trait is favored by natural selection if the benefit to others (b), multiplied by relatedness (r), exceeds the cost to self (c)
rb > c
rb > c
where b = sum of fitness benefits to all recipients
c = cost to giver
r = coefficient of relatedness between them
Coefficient of Relatedness (r)
Measures genetic relationship between interacting individuals
or the average probability that they share an allele from a common ancestor
Relationships and r
Parent and offspring = 0.5
Full siblings = 0.5
half siblings = 0.25
first cousins 0.125
unrelated = 0
r decreases as you become more distantly related to kin
Hamilton’s Rule Has Two Predictions
1) altruism should be directed towards kin (because r = 0 for unrelated individuals)
2) closer genetic relatedness allows for more costly altruism
Kin Recognition
- phenotypic matching = smell or likeness to self
- contextual cues = familiarity, proximity, observe patterns of associations
Maternal Kin
- easier to recognize
- contextual clues, identify siblings as those who spend time with mom too
Paternal Kin
- harder to identify
- age may provide clues in polygynous species (age-liked peers likely fathered by same male)
Examples of Altruism
- grooming (more common among kin)
- Coalitions (supporting individuals during conflicts)
Male Coalitions
- males do cooperate even though they compete for mates
- coalitions last longer + more intense when males are related
- coalitions to take over groups, mutual defense of territory
- cooperate breeding (polyandry)
Parent-Offspring Conflict
fitness of future offspring comes at expense of current offspring
mother wants to invest in future offspring
current offspring want mother to continue to invest in them
Reciprocal Altruism
altruism can evolve even among non-kin if behavior is balanced between partners over time
reciprocity, not kinship, drives this type of altruism
Requirements for Reciprocal Altruism
- frequent interactions
- ability to keep track of support given & received
- must provide support only to those who help
Beyond Kin
reciprocal altruism, altruism between non-kin can evolve if the exchange of benefits is balanced over time
Nonrandom Social Interactions
altruists are more likely to associate with other altruists (both kin or unrelated)
