How do we categorize interactions?
Vis a vis effects on FITNESS - in terms of costs and benefits
Actor's fitness can be selfish while being negative for recipients fitness
- Selfish behaviors
Mutualistic behaviors: actors fitness enhance recipient fitness
- Work together to protect territo
Mutualism
* Two or more individuals engage in behavior that benefit BOTH
*More well off
- Group territorial defense
- Predator mobbing = 2 of more individuals aggression against a predator
Will natural selection favor cooperation?
Recall Darwin's postulates
Traits that allow individuals to reproduce are
more successfully that others in a population
and will become
more
common
Individuals are competing with others in their group for
Differential reproductive success
What are some assumptions that can be made?
A population of individuals who practice reproductive restraint for the
good of the group
- any time a mutation can arise that breaks it (no restraint)
- works in any dynamic where individual are assumed to impose a cost to themselves while benefiting oth
What is unlikely in sexually reproducing species?
GROUP SELECTION
- Most likely not explanation for altruism either
* Group A vs Group B
- Have to be significant variation between both groups - natural selection acting
- 2 groups of SAME SPECIES
* Migrating between the groups to AVOID interbreeding
* Dif
What has to happen for selection to take place at the group level?
In order for selection to take place at the group level , there has to be SIGNIFICANT genetic variation between the two groups
What is the problem with altruism?
Natural Selection favors behaviors that increase relative fitness of individuals
- BENEFICIAL to self, COSTLY to others
Mutualism increase fitness to self and others
Altruism reduces fitness of self and increases fitness of others
.........So now what, no
How does cooperation occur in nature?
1. Alarm calls
2. Cooperative hunting
3. Territorial defense
4. Food sharing
5. Communal care of young
What are 2 ways for selection to favor genes/alleles underlying cooperative behavior individuals?
Inclusive fitness/kin selection
- Help related others who share genes
Reciprocal altruism
- Altruism reciprocated by recipient of benefit (time delay from mutualism)
-
Can't just have random act that benefits others and costing you
-----> Will never work
What must happen in order for altruism to evolve?
Must limit altruism to other altruists
Relatives tend to share genes through COMMON DECENT
- Cooperation requires explanation with shared genes (altruism)
Get behavior to stabilize population
When is altruism favored by kin selection?
B
enefits to recipient x
R
elatedness (actor, recipient) >
C
ost to Actor
This is known as Hamilton's rule:
br>c
What does Hamilton's rule gives us insight about?
Hamilton's rule gives us insight about
distribution of altruism
~ br>c implies
1. No altruism toward
non-kin
(r=0)
2. Altruism biased toward
closer
kin
3. The benefits of kin must OUTWEIGH the cost to the actor in order for alleles underlying cooperation
Example of Hamilton's Rule
Ex: Mom perform behavior (actor) (kin selection)
* Daughter 1 and 2 50% mom's genes
* 2 grandchildren: each 25%
150% shared genes TOTAL
* Mom protect them at all costs
Altruistic behavior allowed 150% to make another day of selection
* Benefit has to outw
What role does kin selection play in primate groups?
Evidence for cooperative behavior among kin
- Grooming
- Coalitions
- Cooperative Breeding
What is widespread around primates?
NEOTISM (non-singal bed single)
Dwarf lemurs forage alone, but settle near female
kin
Male siamangs carry their offsprin often
� Female bonobos form bonds with sons
� Callitrichid infants are provisioned and carried
mainly by related group members
� Femal
Kin Biases in behavior: Grooming (Kin)
Grooming
- most instances between infant and mother
- occur more often between kin than distant kin or nonkin
Kin Biases in Behavior: Coalitions
Coalitions/alliances form during despute
Qualify as
Altruism
- benefit: may result in victory in dominance
- cost: risk of injury
KBIB: Coalitions (Maternal Support)
Maternal rank transferred offspring in many primates
- matrilineage hierarchies
- stability in female hierarchies
Kin Recognition
Contextual cues
- Infants in contact with mother
- Siblings connected through mother
What does the mother know and not know?
- Brain organized to recognize kin through smell or likeness themselves...known as
Phenotypic matching
- DIFFICULT TO TELL
- Indiv
What do primates rely on to recognize kin?
FAMILIARITY
Remember: Mothers don't seem to recognize own infants at birth
Within few weeks, mothers discriminate between own infant and strange infant
How do females recognize other maternal relatives?
Through Mother-infant associations
Mothers and infants stay close together
- Juveniles remains close to mothers
Infants become familiar with older siblings because both are near mother
Mothers maintain ties to adult daughters, and become familiar with gra
Should we expect kin recognition in the wild?
Conventional wisdom:
Paternity certainty is LOW
Pare bonded species: extra pair copulations
One-male groups: incursions from nonresident males
Multi-male groups: females mate with many males
- no long term pair bonds
What might primates use to guess paternity?
Rules of Thumb
If alpha male monopolizes matings
- all infants born during his tenure = his offspring
- all infants born during his tenure = paternal siblings
Males can't be related to kids conceived before they arrived
Males can't be related to kids unle
Understanding parent offspring conflict
Fitness of future offspring comes at expense of current offspring
- Mothers have to balance care of current offpsirng against future offspring
- Limits on the care benefits mother but not the current offspring
Most obvious in weaning conflict: mom motivat
What can reciprocal altruism favor?
Altruism among nonkin
Altruism exchanged between reciprocal partners
- A help B if B help A
- they are better off than doing nothing
What does reciprocal altruism require?
1. Frequent opportunities to interact (proximity)
2. Keep track of help given and received (memory)
3. Must only help if receive help (contingent discriminating behavior)
Notice:
Non-random interactions
If doing costly things for random individuals and ge
What is it that primates ought to be good candidates for?
Reciprocity
Grooming: A grooms B; B grooms A
- Better off from the interaction: both won't have parasites
1. Stable social groups
2. good memories
3. flexible behavior
Reciprocity in Grooming
Spending equal amount of time with one another
Studies indicate that primates can keep track of contingencies over short periods of time
- balance within bouts
- balance between bouts
Do monkeys trade grooming in for support?
Grooming and support are altruistic
Groomees might "repay" groomers by aiding them
- Such as in food or support in conflict
Predict: Recent grooming makes monkeys more likely to respond to requests for help
- grooming traded for aid
- monkeys more attenti
What is the importance of reciprocity?
Most examples involve exchanges of LOW COST commodities in
short span of time
- almost simultaneous, which looks more like mtualism
Including individuals that are related to each other (kin selection)
- not clear whether reciprocity is contingent
- correl
What are the mechanism for underlying cooperation in primate groups?
Very strong evidence for kin selection
Mixed evidence for reciprocal altruism