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Lecture 7

Lecture 7

2 Pages
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Department
Anthropology
Course Code
ANTB14H3
Professor
Michael Schillaci

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Chapter 7a (pp. 176-191): The Evolution of Cooperation
Week 6
Altruistic behaviours: benefit other but at a personal cost
oExample, primates groom other group members, removing parasites, cleaning scabs,
picking bits of debris from hair
oGrooming others consumes time that could be spent looking for food, courting, caring for
offspring, or scanning for predators
oNatural selection can favour evolution of altruistic behaviour
Mutualism
Provide benefits to both participants
Most likely to work if slacking off isnt profitable for any of participants
Coalitions among male baboons may be an example
oEast Africa, male baboons guard receptive females
oOn days females most likely to conceive, highest ranking males usually attempt to
monopolize access to females
o2 lower ranking males may jointly challenge higher ranking male and try to gain control of
female he is guarding
Problem with group-level explanations
Altruistic behaviours cannot be favoured by selection just because they are beneficial to group as
whole
Example, alarm calls in monkeys, not favoured, because callers and noncallers benefits from a
callers group, but at the cost of the caller- predator may hear them.
Genes that cause alarm calling will not be favoured by selection
Kin selection
Natural selection can favour altruistic behaviour if altruistic individuals are more likely to interact
with each other than chance alone would dictate
Callers in relatives are favoured
Calling will be favoured by natural selection only if its benefits are sufficiently greater than its
costs
Hamiltons Rule
Predicts that altruistic behaviours will be favoured by selection if costs of performing behaviour are
less than benefits discounted by coefficient of relatedness between actor and recipient
Kin selection: selection could favour altruistic alleles if animals interacted selectively with their
genetic relatives
Act will be favoured by selection if:
rb>c
r = average coefficient of relatedness between actor and recipients
b = sum of fitness benefits to all individuals affected by behaviour
c = fitness cost to individual performing behaviour
Coefficient of relatedness (r) measures genetic relationship between interacting individuals
or is average probability that 2 individuals will acquire same allele through descent from
common ancestor
Hamiltons rule leads to two important insights:
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Description
Chapter 7a (pp. 176-191): The Evolution of Cooperation Week 6 Altruistic behaviours: benefit other but at a personal cost o Example, primates groom other group members, removing parasites, cleaning scabs, picking bits of debris from hair o Grooming others consumes time that could be spent looking for food, courting, caring for offspring, or scanning for predators o Natural selection can favour evolution of altruistic behaviour Mutualism Provide benefits to both participants Most likely to work if slacking off isnt profitable for any of participants Coalitions among male baboons may be an example o East Africa, male baboons guard receptive females o On days females most likely to conceive, highest ranking males usually attempt to monopolize access to females o 2 lower ranking males may jointly challenge higher ranking male and try to gain control of female he is guarding Problem with group-level explanations Altruistic behaviours cannot be favoured by selection just because they are beneficial to group as whole Example, alarm calls in monkeys, not favoured, because callers and noncallers benefits from a callers group, but at the cost of the caller- predator may hear them.
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