Problem 4 Flashcards
Levels of selection debate
Refers to a debate concerning which level of biological organization, natural selection is best seen as acting at
e.g.: genes, individuals, populations
Wynne Edwards explanation for reproductive restraint in birds
According to him, birds hatch less eggs during a scarce period so that the whole population will survive
–> altruism has to be able to outcompete selfishness, for the theory to work
Why is Wynne-Edwards explanation wrong ?
Altruism will not outcompete selfishness as it will eventually go extinct
–> as altruists only lay one egg as opposed to selfish ones, they will be disadvantaged relative to their competitors within the group
Evolutionary stable strategy (ESS)
Refers to a behavioral policy that, once common in a population, cannot be outcompeted by any alternative behavioral policy
ex.: selfishness
Why are altruistic alleles disadvantaged as opposed to selfish alleles ? Why do they go extinct ?
Because the average fitness of the selfish allele is higher than that of the altruistic allele
–> this means it will eventually go into fixation
Kin selection (Hamilton)
Refers to natural selection in which an apparently disadvantageous characteristic increases in the population due to increased survival of individuals genetically related to those possessing the characteristic
–> central component is the coefficient of relatedness
ex.: altruistic traits
Hamiltons rule
States that kin selection causes specific genes to increase in frequency when the genetic relatedness of a recipient to an actor multiplied by the benefit to the recipient is greater than the reproductive cost to the actor
Formula for Hamiltons rule
C < 1/2 x b
c= reduction in the actors reproductive success/cost
b= increase in the recipients reproductive success/benefit
r=1/2 –> coefficient of relatedness
Inclusive fitness
Refers to an individual’s direct fitness + any other additional fitness of its relatives resulting from helping him, adjusted by the coefficient of relatedness
–> sum of direct + indirect fitness
Alloparenting
Investing in or providing parental care to any non-direct offspring
–> kin selection plays a strong role
What are the constraints on hamilton’s rule ?
- A behavior will not evolve, if C is too large in absolute terms
- R is not sufficient to predict which behaviors will evolve
–> b + c are variable depending on the future prospects of the recipient + actor
Why can behaviors that benefit relatives at the expense of the actor evolve according to Hamilton ?
Because of allelic relatedness between kin
True altruism
Develops if a cooperation behavior, negatively affects the actors lifetime reproductive success
–> evolves + is maintained through kin selection
ex.: parental care
Mutual-benefit behaviors
Develops if a cooperation behavior, positively affects the lifetime reproductive success of both the recipient + actor
–> can only be maintained if cheating strategies can be prevented from prospering
Cheating
Taking the benefits of joint ventures without paying the cost
By-product benefit
Occurs when the benefits to others arise simply as a side effect of the benefit to the actor
–> no cooperation, therefore no cheating
Direct reciprocity
Refers to the idea that we help individuals who have helped us in the past
–> possible mechanism for the evolution of mutual-benefit behavior
ex.: Prisoners dilemma
Indirect reciprocity
Refers to the idea that it might be advantageous to help individuals who we have seen helping others in the past, even if that help wasn’t specifically directed to us
Punishment
Providing punishment is a form of cooperation
–> can make cooperation stable even in the absence of direct reciprocity
Humans are notable for the extent of their cooperation. Why is that ?
- They have direct reciprocal one-on-one relationships
ex. : friendships, marriages - Collective actions/Contribution to joint ventures
–> the costs are potentially very large, but are sustained by a combination of danger of ostracism or punishment
ex.: going to war
Ultimate explanations
Are concerned with why a behavior exists
–> respectively the fitness consequences of a trait or behavior and whether it is (or is not) selected
Proximate explanations
Are concerned with how a certain behavior works
–> respectively the mechanisms that underpin the trait or behavior
Tit for tat
Cooperate in the first round, and then do what the other just did to you
Grudgers
Is a strategy where one first always co-operates unless the other defects – then he only defects
Stay-loose shift
Keeping the strategy if you win, but changing it when you loose
Joss
Strategy that is basically tit for that, but sometimes tries defecting
Tester
Is a strategy which starts of cooperating and then defects to see what the opponent does and to find out their strategy
Indirect fitness
Refer to the genes that contribute to the next generation by an individual indirectly via helping relatives
–> offsprings produced by relatives
Direct fitness
Refer to the genes that contribute to the next generation by an individual directly via reproduction
–> direct offsprings
Parochial altruism
Altruism within a group has co-evolved with hostile behaviour towards the other group, factors combined result in fitness benefit
–> reduces fitness
Eusociality
Highest level of organization of animal sociality, is defined by
- cooperative brood care
–> individuals older than parents assist in raising the offspring
- overlapping generations within a colony of adults
- division of labour into reproductive and non-reproductive groups/ reproductive altruism
- philopatry
–> individuals remain living in their birthplace
ex.: bees
Reproductive altruism
Behaviour that increases other organisms’ fitness and permanently decreases the actor’s own fitness
Network reciprocity Formula ?
Social networks imply that some individuals interact more often than others
FORMULA: b/c>k
–> The benefit-to-cost ratio must exceed the average number of neighbours (k) per individual
Reproductive restraint
Refers to adaptation that has evolved because it increases the likelihood of the population surviving through bad years
What are the benefits of tit for tat ?
It is
a) Nice
* never cheats first
b) Retaliatory
* sees cheating and cheats too
c) Forgiving
* forgives earlier cheating
Hamiltons explanation on how Eusociality arose in social Hymenoptera
According to him, it arose by kin selection because of their interesting genetic sex determination trait of haplodiploidy
–> males are produced by parthenogenesis, females are produced from fertilized eggs
What is a cooperator ?/ Cooperation ?
Someone who pays a cost (c), for another individual to receive a benefit (b)
–> best for in-group
What is a defector ?/ Defection ?
Someone who has no cost and does not deal out benefits
–> have a higher overall fitness than cooperators
–> selection increases the relative abundance of defectors
–> best for the individual + population
Formula for direct reciprocity
w>c/b
–> the probability (w) of another encounter between the same two individuals has to exceed the cost-to-benefit ratio of the altruistic act
Formula for indirect reciprocity
q>c/b
–> the probability (q) of knowing someone’s reputation has to exceed the cost-to-benefit ratio of the altruistic act
Fitness
Refers to the ability of an individual to survive and reproduce in an environment, compared to other individuals in the population
Green beard effect
Refers to a situation where one favors the carriers of a certain gene that can be seen by phenotypic effects
ex.: Green beard people help each other, but not others
Group selection
In a group, selfish individuals will beat altruistic individuals but between them, groups of altruistic individuals beat groups of selfish individuals
Multi level selection
Selection acts on individual organisms but also on groups
- The population is divided in groups, which grow due to offspring
- Once a group has a certain size, it splits in 2
- Now there is selection at 2 levels
–> within group that favors defectors and between group that favors cooperators
