Birupakshya Paul ChoudhuryM.Sc. 3 rd semester
Dept of Life Science and BioinformaticsASSAM UNIVERSITY
Altruism and EvolutionKin Selection Group selection
Reciprocal Altruism
Derived from : French - “Autrui” meaning other people Latin - “Alter” meaning otherThe term was Coined by- Aguste Comte (French)
Altruism is a type of social behaviour where the actor is harmed while others get benefit
In evolutionary biology, an organism is said to behave altruistically when its behaviour benefits other organisms, at a cost to itself
Costs and benefits are measured in terms of reproductive fitness
Altruism
Why did Altruistic behaviour evolve where natural selection persists
In a group there are members who are selfish, so how can the altruists thrive in the population
Idea of altruism seems to go completely against the Darwinian idea of ‘survival of the fittest’
How does Altruism exists within Natural Selection?
??!!!
To explain the altruistic behaviors of animals in the light of evolution, we need to discuss the following:
A.Group selectionB.Kin selectionC.Reciprocal altruism
In The ‘Descent of Man’ (1871), Darwin discussed origin of altruistic and self-sacrificial behaviour among humans
Almost all animals including humans show altruistic behaviour in their respective society
Lets find out the reasons behind Animal altruism
Explanation of Altruism
It is a type of natural selection, that acts on all members of a group i.e. the whole group is favored over another group
Defined as a selection which evolves according to fitness of groupsHas two Concepts- 1) Old Concept 2) New Concept
Group Selection
In 1960, Wynne Edwards argued that individual selection could not explain subordination of selfish interests to promote group wellbeing
For example, in groups consisting of selfish individuals (who reproduce at the maximum rate), resources would be over exploited, and the group would go extinct. In contrast, groups consisting of cooperative individuals who restricted their birth rate would not over exploit their resources, and not go extinct
This came to be known as the Old concept of group selection
Group Selection- Old concept
During the 1960s and 1970s a large body of theoretical work was piled up against the idea of Wynne Edwards’ Old Concept
Maynard Smith (1976) showed that group selection would not work if the number of individuals who disperse and reproduce elsewhere (successful migrants) is greater then one per group
Empirical works showed that individuals who were reproducing at the rate that maximized their lifetime reproductive success, and were not practising reproductive restraint
Basic idea behind this concept is at certain stages of an organism's life cycle, interactions take place between only a small number of individuals. & under these conditions, cooperative behaviour can be favored.
Group Selection- New concept
Sometimes referred to as ‘trait-group selection’ or ‘demic selection’ or ‘intrademic’ selection
Difference between the old and new group selection models is that the new group selection models rely on within-population (intrademic) group selection,
Whereas old group selection theory worked on between-population (interdemic) group selection
Group Selection- New concept
Groups
SelfishAltruists
“Kin selection” was coined by Maynard Smith Also known as Inclusive Fitness TheoryHere, an individual has the tendency to help its relativesThe inclusive fitness theory (commonly known as Kin selection) was
proposed by Hamilton (1964)- HAMILTON’s RULElet B = Benefit to Recipientlet C = Cost to Actorlet r = Coefficient of their genetic relatedness
In this case, An allele for an altruistic behavior will be favored if:Br – C > 0
r is the probability that homologous alleles present in different individuals are “identical by descent”.
Kin selection
William Hamilton
Jerram Brown pointed out that the inclusive fitness of an individual is dividedinto two components:
I.‘Direct Fitness’II.‘Indirect Fitness’
Direct fitness is gained through the production of offspring indirect fitness through aiding the reproduction of nondescendent
relatives
Kin selection (contd.)
Basis of this behaviour: A gene that a particular individual carries may pass to the next generation through a related animal
Forego reproduction: Eusociality
Examples of Kin selection
Robert Trivers coined and introduced the theory of ‘reciprocal altruism’ (1971)
In this type of altruism, the altruist acts in a manner that temporarily reduces its fitness with the expectation that the beneficiary organism will act in a similar manner at a later time
This form of altruism may occur among unrelated individuals
Trivers suggested that two conditions must be met:I. Cost must be ≤ to the benefit received.II.Individuals that fail to reciprocate must be
punished.
Reciprocal altruism
Robert Trivers
Summary of social interactions
RECIPIENT BENEFITS
RECIPIENT HARMED
ACTOR BENEFITS ACTOR HARMED
COOPERATIVE ALTRUISTIC
SELFISH SPITEFUL
BIG question to be answered But we have some examples
Altruistic behaviour of Humans
Helping the needy
Blood donation
BIG question to be answered But we have some examples
Exchange gifts
Giving seat in the bus to old/women
Giving away something
permanently for loved ones
Giving the child to childless
uncle in joint families
………… and many more
Caring for pets
Working for animal rights
Sacrificing self for Nation
1. Alan Grefen ‘Natural selection, Kin selection and Group selection’2. David Sloan Wilson ‘A Theory of Group Selection’ (1975)3. Joan B. Silk ‘Reciprocal altruism’4. Kevin R. Foster, Tom Wenseleers, & Francis L.W. Ratnieks ‘Kin
selection is the key to altruism’ (2005)5. Martin Zwick, Jeffrey A. Fletcher ‘Levels of Altruism’ (2014)6. Stuart A. West, Andy Gardner & Ashleigh S. Griffin ‘Altruism’7. S. A. West, A. S. Griffin, A. Gardner‘Social semantics: altruism,
cooperation, mutualism, strong reciprocity and group selection’ (2007)
Reference:
URLs:1. http://science.jrank.org/pages/264/Altruism.html
2. http://plato.stanford.edu/entries/altruism-biological/
3. https://en.wikipedia.org/wiki/Reciprocal_altruism
4. http://www.lse.ac.uk/philosophy/blog/2015/06/19/where-does-altrui
5. http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2006.01258
Reference: