18- Human co-operation

Question 1

what is cooperation and altruism

Answer 1

cooperation: a behaviour which provides a benefit to another individual and which is selected for because of its beneficial effect on the recipient

altruism: a behaviour that is costly to the actor and beneficial to the recipients. costs and benefits are defined on the basis of the lifetime direct fitness consequences of a behaviour

Question 2

cooperation example

Answer 2

cleaning mutualisms

not cooperation: dung production by elephants

Question 3

altruism example

Answer 3

alarm calling?

Question 4

why cooperate?

Answer 4

can be sometimes explained by direct benefits - but not always. altruism is an evolutionary puzzle

Question 5

puzzle of altruism

Answer 5

“natural selection will never produce in a being anything injurious to itself, for natural selection acts solely by and for the good of each”

origin of species, 1859

Question 6

Group selection

Answer 6

proposed as solution in the early-mid C20th

idea that organisms behave altruistically for the good of the species of population e.g. foregoing reproduction to avoid overpopulation (Wynne-Edwards)

Question 7

Genes eye view

Answer 7

Natural selection works at the level of the gene (competition between alleles)

But ‘selfish gene’ a metaphor, genes do not always favour selfish behaviour

Richard Dawkins

Question 8

kin selection

Answer 8

cooperate selectively with genetic relatives

“I would lay down my life for two brothers or eight cousins” - JBS Haldane

Question 9

Hamiltons rule

Answer 9

alleles devouring altruistic behaviour can evolve when rB > C

r = coefficient of relatedness
B = benefit to recipient
C = cost to helper

Question 10

Examples of Kin selection and altruism

Answer 10

Alarm calling = beldings ground squirrel (calls more often when more relatives around)

Cooperative breeding = pied kingfishers (offspring often stay with parents to help rear younger siblings)

Question 11

eurosociality

Answer 11

cooperative breeding with reproductive and non reproductive ‘castes’ e.g. honeybees and naked mole rats

relatedness within groups high in eusocial species (haplodipoidy in insects)

Question 12

What about humans?

Answer 12

all humans recognise and categorise kin relationships.

Detailed analysis of axe fight in Yanomamo village, Venezuela 1971:
- fight began when local woman refused to give vistor some of her crops
- visitor attacks her, fight escalades as supporters get incolced
- supporters more closely related to each other than opponents

Question 13

reciprocal altruism

Answer 13

Trade favours: cooperate selectively with those who help you in return

Robert Trivers

Question 14

prisoners dilema - reciprocal altruism

Answer 14

‘tragedy of the commons’ : mutual cooperation best for all
BUT individually better to exploit the cooperation of others
Tit for tat strategy favoured if interactions repeated (game theory)

How could altruism evolve given this temptation

Question 15

reciprocity example

Answer 15

few examples in non humans, even classic example debated.
vampire bats:
- reliant on the blood of other animals for food
- success rates variable, risk starvation
- will donate food to hungry groups members
- groups contain kin and non kin members
- sharing more likely between kin relatives
- but also non kin who associate more

Question 16

what about humans?

Answer 16

average genetic relatedness fairly low in hunter-gatherer communities - cooperation with non-kin essential

reciprocal gift giving often vital for between-group relationships e.g. kula ring - ceremonial gift giving, implicit obligation to reciprocate

friendships are reciprocal and require reciprocal exchange

Question 17

Human cooperation special issues

Answer 17

very large scales, not limited to kin or potential reciprocators

large charities

50% of ‘golden balls’ contestants chose to ‘split’ rather than ‘steal’

Question 18

why cooperate with non kin and those unlikely to reciprocate

Answer 18

1. evolutionary mismatch - Current conditions not representative of ancestral human communities (small groups of kin + known non-kin)
2. cultural group selection - variation and competition between cultural groups favours large scale, generalised cooperation with group members

currently a matter of debate and disagreement!

Question 19

evolutionary mismatch

Answer 19

plausible given other examples of evolutionary mismatch. But - encounters with strangers not that evolutionary novel

Question 20

cultural group selection

Answer 20

supported by between group variation in cooperative behaviour. But - also extrinsic variation in the cooperative behaviour within groups