Evolutionary changes in brain size Flashcards
describe the relationship of body size to brain size
the smaller the animal –> the larger the brain in proportion to body
what is determined through allometric scaling of brain and body
brain grows more slowly compared to body size
what can be said about the allometric relation of the brain in humans compared to other species
humans lie above “best fit” line
have larger brains that should have in relation to body size
what is the encephalization quotient (Harry Jerison)
observed brain weight vs expected brain weight
closer to line – more expected
further away – more statistically significant
challenges in allometric studies
Sampling issues : calculations depends on the data points (taxonomic groups) included in the analysis
Different scaling exponents : different taxonomic groups may have scaling exponents other than 2/3
what can be said about relative brain size in vertebrate evolution
relative brain size has increased in most taxonomic groups
taxa that increased in relative brain size experience more diversification
what is the clever foraging hypothesis
suggests that having larger relative brain provides better advantage to adapting to natural environment
Species with greater relative brain size hunt strategically vs. less encephalized species that find food opportunistically
what is the social (Machiavellian) intelligence hypothesis
Suggests most intelligent animals are highly social, and form alliances (friendships)
Suggested that larger relative brain are also more related in deception of others for resources (Machiavellian intelligence)
what is the social brain hypothesis
Larger relative brain size in primates evolved to manage complex social systems
Correlation found between brain size (relative neocortex volume) and group size (proxy of social complexity)
what is the best predictor for cognitive ability among non-human primates
absolute brain size
what can be said about brain size and cortical thickness / density
Cortical thickness –> NOT correlated with brain volume, Larger brain mammals have thinner cortex
Cortical Neuronal density negatively correlated with brain size, Brains that are larger have more spaced neurons –> allows for longer axons and better connection
how much of our metabolism doe sour brain consume
its is 2% of our body weight but consumes 20% of our metabolism –> very expensive organ
