Birupakshya Paul ChoudhuryM.Sc. 3 rd semester

Dept of Life Science and BioinformaticsASSAM UNIVERSITY

Altruism and EvolutionKin Selection Group selection

Reciprocal Altruism

Altruism or Selfishness ??

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

Examples of Reciprocal altruism

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

Conclusion

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:

Thank You