NBB 201 Lecture 14: Oct30Notes
7 Nov 2018
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• Testosterone might facilitate aggression, but it is not aggression!
• Cortisol – stress
• Aggression in mating fitness!!!
Aggression:
• Fancy folk theories:
o Argues that aggression is inevitable, aggression builds up and is random – Lorenz
o Sussman and Garber – looked at primate species and how much time did they
spend in social interactions and how much of that time were they aggressive
▪ If the dominant male is displaced, that might increase aggression time! –
Making it a “folk” story
▪ Species might be different in terms of hierarchies – making it “folk”
• Behavioral Ecology:
o Certain contexts in which it makes “Sense” to be aggressive – cost and fitness
• Sexual Selection
o How you interact with others in your group
▪ Intersexual (between the sexes) – male and female interactions
▪ Intrasexual (within a sex) – males competing with other males to mate
with a female for example
• Because they are competing for the same resources – in this case,
their ability to mate with females
• Females are competing for a preferred partner (a good, strong
dominant male). Takes energy to make offspring – food resources
– in order to produce viable offspring
o INFANTICIDE AS A MALE INTRASEXUAL COMPETETION!!!!!
o Female counterstrategies as intrasexual competition:
▪ Why don’t females evolve to be larger than males to better protect
infants?
• B/C females are competing with each other
o Males are limited to mating opportunities with females
• Male Competition:
o Strength of intersexual competition is high → males are larger than females
(have ornaments)
o Males have higher potential reproductive rates than females because they invest
less energy than females. Because they move on to females very quickly!
▪ This means there is a greater disparity between top and bottom males
because other males are left out!
• E.g. Gagnes Khan – Mongolia – 20% have shared y-chromosome –
he mated with a lot of people to spread his genes
• Hunter-gatheres – egalitarian society
o Females have tighter distribution between number of kids they have (Around 7-
8)
