Intelligence Flashcards
brain metabolic costs
- use 20% of resting energy (10% for primates and 5% for non-primates
- needs; higher quality meaty diet, fat-for-muscle tradeoffs
- 60% of energy goes to brain development in babies
brain maternal costs
- larger head fitting through a narrower pelvis (bipedalism)
- Obstetrics Dilemma
Obstetrics Dilemma
trade-off between infant brain size, dependency period, female pelvic width, and childbirth mortality
equation showing what makes brains evolutionarily worth it
metabolic costs + maternal costs < adaptive benefits
Four theories for rapid human brain size increase in the past 2 million years
Wallace’s theory- creationism
Darwin and Fisher’s theory- sexual selection and runaway sexual selection
Dunbar’s theory- Social Brain Hypothesis
Henrich’s theory- Cultural Brain Hypothesis
Wallace’s intelligence theory
creationism- a higher power bestowed our “humanness upon us
Darwin’s intelligence theory
sexual selection- it was favourable for a mate to be more intelligent and was therefore selected for
Fisher’s intelligence theory
runaway sexual selection- constant selection for bigger and bigger representations cause runaway expansion over time, therefore selection for intelligence led to runaway brain expansion
e.g. Irish elk
why aren’t Darwin and Fisher’s theories supported today?
not enough examples in nature
wouldn’t see bigger brain selection in both sexes, only 1
if intelligence is maladaptive, females would have chosen dumber males with smaller brains
Dunbar’s intelligence theory
Social brain hypothesis- primates with a bigger neo-cortex ratio are more social, have bigger group sizes, and therefore spend more time grooming each other
Dunbar’s number
147.8
what is the neo-cortex ratio?
ratio of the neocortex (top layer of brain) to the rest of the brain
theory on why language developed (social brain theory)
amount of time spent grooming (like other primates) would be unsustainable in humans big social groups, so they created language which is quicker
what is most social language used for?
gossiping and networking, about 80% of the conversation on college campuses
What was the new type of relationship formed in the animal kingdom with the invention of language
friendship
