Altruistic? - a behaviour that is costly to the actor with no benefit
Individual will forgo foraging
Call out to other individuals
If individuals are “selfish”, why do we see cooperative behaviours?
Selection for cooperative groups?
How is selection occurring in populations
How it evolved
Wynne-edward model
2 groups:
S groups overexploit resources and die out
A groups cooperate and live
Selfish individuals will overexploit resources,
take more than needed, group will die off
Cooperative group- share resources equally,
group survives
Problem
Individuals dies faster than groups/population
Selection occurring more on individuals
In group of altruistic individuals- selfish individual that comes along and tries to enter group will have
higher fitness than altruistic individuals and will invade population
Selfish individuals entering the population will ha ve higher fitness
Model isn't helpful
Need to find a way to explain cooperative behaviour even though section acts on individuals and
individual fitness
Needs to satisfy condition
Cooperation can evolve when benefits to individual minus costs of producing this behaviour is greater
than zero- individual B-C>0
But some humans are “resilient” co-operators in the long run…
Game people were asked to play
Rounds of game
Cooperate or defect
Play for 10 rounds each day over successive days
The amount of cooperation starts high then declines within the day and over different days
There were some resilient cooperators- don't defect on others
Cooperation was maintained by these individuals in the population
Need to alter the lifetime payoffs for cooperation and defection…
, Direct benefits – mutually beneficial
Indirect benefits – can explain altruism
Kin selection
Inclusive fitness
You can achieve full fitness (having a full copy of genes in the next generation) without producing
your own offspring!
Evolutionary fitness- how many offspring an individual can produce
Gain fitness through offspring of relatives
Can achieve full fitness without having to produce own offspring if they can help relatives produce
offspring
Hamilton’s rule
Rb-C > 0
B – benefit to the recipient
C – cost to the actor
R – genetic relatedness
The more related the actor is to the recipient (i.e. The bigger r is), the bigger the cost can be.
Change equation of whether we expect cooperation to evolve
Benefits and costs
Genetic relatedness between actor and recipient
How do we calculate r?
R = Σ (0.5)L
Where L is a generation link,
sum across all possible
pathways
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