2A) You are the first to arrive at the scene of a house fire. You hear somebody in the house
calling for help. Ignore the notion of helping people for the sake of helping people (a noble thing
and highly recommended, but not immediately relevant here). In your own words, explain why
it may be selectively advantageous for you to help, and risk serious injury or death in the
process, if the person calling is a close relative. What if that person is a stranger? I am looking
for a narrative explanation, not just a formula.
2B) Jane is an ant, an organism with a haplo-diploid mating system (females are diploid, males
are haploid). In a parallel of J.B.S. Haldane’s statement, should Jane give up her life to save two
of her sisters? Assume all ants can reproduce and will produce 2 offspring (neither is correct in
reality, but assume it for your calculations). List all of your calculations, and your reasoning on
why you plugged in specific numbers.
Solution
Answers:
2. (A) The concept of self-sacrificial behaviour was provided by William D. Hamilton.
According to his arguements, natural selection favours genetic success, not reproductive success,
and that individuals can pass copies of their genes on to future generations.
Genes are passed from direct parentage and by assisting the reproduction of close relatives a
concept referred to as kin selection.
The conditions under which reproductive altruism evolves:
r × B > C, where r = genetic relatedness of the altruist to the beneficiary, B = Benefit received by
the recipient, C = Cost incurred/suffered by the donor.
The coefficient of relatedness is different between everyone
r =1/2 for parents/offspring
r = 1/2 for siblings
r = 1 for offspring and themselves
r = 1/4 for half sibling
Siblings are related by 1 to themselves but 1/2 to each other, while parents are equally related to
all their offspring.
So, its a fair deal in evolutionary terms if the person to be saved is a close relative like
offsprings, siblings aorparents, but not for a stranger since r = 0.0 in a life and death situation.
(B) Half of its genome comes from the father (haploid) and half from the mother (diploid). That
means she carries all of her fathers genes and half of her mother’s genes. So does her sister,
implying that they share of course the entire genome of their common father (i.e. already 50% of
their genome), plus, on average, a quarter of their mother’s genome, yielding a coefficient of
relatedness of 0.75.
r for one sister = 0.75
So, r for two sisters = 0.75 + 0.75 = 1.5
Thus, the cost suffered by Jane is less than the benefit gained by the two sisters. So, Jane should
give up her life to save her two sisters..
2A) You are the first to arrive at the scene of a house fire. You he.pdf
1. 2A) You are the first to arrive at the scene of a house fire. You hear somebody in the house
calling for help. Ignore the notion of helping people for the sake of helping people (a noble thing
and highly recommended, but not immediately relevant here). In your own words, explain why
it may be selectively advantageous for you to help, and risk serious injury or death in the
process, if the person calling is a close relative. What if that person is a stranger? I am looking
for a narrative explanation, not just a formula.
2B) Jane is an ant, an organism with a haplo-diploid mating system (females are diploid, males
are haploid). In a parallel of J.B.S. Haldane’s statement, should Jane give up her life to save two
of her sisters? Assume all ants can reproduce and will produce 2 offspring (neither is correct in
reality, but assume it for your calculations). List all of your calculations, and your reasoning on
why you plugged in specific numbers.
Solution
Answers:
2. (A) The concept of self-sacrificial behaviour was provided by William D. Hamilton.
According to his arguements, natural selection favours genetic success, not reproductive success,
and that individuals can pass copies of their genes on to future generations.
Genes are passed from direct parentage and by assisting the reproduction of close relatives a
concept referred to as kin selection.
The conditions under which reproductive altruism evolves:
r × B > C, where r = genetic relatedness of the altruist to the beneficiary, B = Benefit received by
the recipient, C = Cost incurred/suffered by the donor.
The coefficient of relatedness is different between everyone
r =1/2 for parents/offspring
r = 1/2 for siblings
r = 1 for offspring and themselves
r = 1/4 for half sibling
Siblings are related by 1 to themselves but 1/2 to each other, while parents are equally related to
all their offspring.
So, its a fair deal in evolutionary terms if the person to be saved is a close relative like
offsprings, siblings aorparents, but not for a stranger since r = 0.0 in a life and death situation.
(B) Half of its genome comes from the father (haploid) and half from the mother (diploid). That
means she carries all of her fathers genes and half of her mother’s genes. So does her sister,
implying that they share of course the entire genome of their common father (i.e. already 50% of
2. their genome), plus, on average, a quarter of their mother’s genome, yielding a coefficient of
relatedness of 0.75.
r for one sister = 0.75
So, r for two sisters = 0.75 + 0.75 = 1.5
Thus, the cost suffered by Jane is less than the benefit gained by the two sisters. So, Jane should
give up her life to save her two sisters.
