Preferences in Sexual selection
Parental investment for women
Waist to hip ratio for men
Men- worse is sexually (you could have to raise someone elses offspring)
Women – worse is emotionally, he could withdraw his parental investment
- why does it happen
- which competes, which chooses
- can it operate on both sexes? (Yes, esp. in humans however there are sex
differences in sexual selective traits)
- nature of jealousy between sexes is usually very different
Cooperation and Conflict
- altruistic/self-sacrificial behavior on behalf of another group of organism is a
puzzle for evolutionary biology
- selection is fundamentally competitive so why help others?
- How can group living and cooperation be common?
Actor Actor is
Recipient Cooperation Altruism
Recipient Selfishness Spite
Types of Social Interaction
- actor benefits or is harmed
- recipient benefits or is harmed
- exampels of spite in nature are extremely rare
- how can we explain altruism?
Altruism is a “special difficulty, which at first appeared to me insuperable, and
actually fatal to my whole theory” – Darwin
- how can we explain behaviours that appear to sacrifice the fitness of an
individual and benefit the fitness of others?
Ex. Mother squirrels have to call out to offspring so they know a predator is coming.
Increases risk for mother as the predator can then locate the mother but the babies
are nonsensible and would otherwise not survive. Kin selection altruism. Ex. Type of birds forego their own opportunity for reproduction to help produce
How can traits reducing fitness (offspring production) be selectively favoured?
- Sacrificing individual fitness for the good of the group? NO
- Kin selection
- personal reproduction direct fitness
- More to “fitness” than simply producing direct descendants
- more of a chance of your alleles surviving sometimes in helping those closely
- based on the idea that there is more than one way to get your genes to the next
- directly or indirectly through increasing survivability of close relatives
- additional reproduction by relatives due to ‘altruism’ indirect fitness
- inclusive fitness = direct + indirect fitness
Kin selection – favours traits that increase indirect fitness
Hamilton’s Rule determines whether ‘altruistic’ traits favoured: rb>c
- does selection favour spread of altruistic trait?
- degree to which donors relatives benefit (b)
- weighted by degree of relationship (r)
- does this outweigh costs to donor’s direct fitness (c) ?
“I would lay down my life to save two of my brothers or eight of my cousins, but nine
cousins would outweigh the two brothers in genetic fitness”
- blood sharing in vampire bats
- cooperation, reciprocity, and the Prisoner’s Dilemma
- punishment depe