31 - Evolution Flashcards
In what way do vertebrate brains differ?
All things being equal, smaller animals have proportionately larger brains
In what ways have brains changed? (3)
1) Overall size - Bigger brains
Bird, mammals and cartilaginous fish have increased relative brain size
2) Relative regional size increases - esp. neocortical signalling (more neocortex)
3) Brain architecture design (lamination, migration, segregation, mappings) esp. neocortical parcellation
Are bigger brains more sophisticated brains?
No - a whale may have more neocortex but not necessarily more complicated
Are smaller brains less sophisticated brains?
No - a fish brain can have at least 15 types of different organisations
Primate brains show same/different levels of gyrification (folds of cerebral cortex)?
Different
What brain feature hasn’t changed?
Cortical layer thickness, 6 layers
Benefits of thinner cortex rather than having an 8 layer cortex to try and get more cells in?
Tighter folding because thick cortexes need to spread out folding more
Homo erectus was found in 3 continents
Africa, Europe, Asia
The evolution of grassland = driver of evolutionary change towards intelligence [ie freeing the forelimbs to allow hands to make tools etc.]
But, brain size has increased well after bipedalism: bipeds existed for two million, or even several million, years before brains got bigger than chimp-sized. This suggests that freed hands wasn’t a trigger for cerebral expansion.
The evolution of grassland = driver of evolutionary change towards intelligence [ie freeing the forelimbs to allow hands to make tools etc.]
But, brain size has increased well after bipedalism: bipeds existed for two million, or even several million, years before brains got bigger than chimp-sized. This suggests that freed hands wasn’t a trigger for cerebral expansion.
Variability Selection Hypothesis
Relatively rapid environmental change replaced habitat-specific adaptations and favoured adaptations that increased the ability to respond and accommodate this change (such as increased intelligence and greater social complexity). Problem solvers survive.
Chimp, Australopithecus or human - childbirth is hardest in?
Human
Rates of tooth development are fastest in - aust., h.erectus. h.sapiens?
Aust. - move to adult diet quickly from birth
Homo floresiensis - they fit both aust. and homo lineages
-had a brain size similar to chimps
Homo floresiensis - they fit both aust. and homo lineages
-had a brain size similar to chimps
Do monkeys and humans both have brocas area (for language)?
Yes but they don’t have the capacity for generative language
What made brains bigger?
Pressure for bigger brains (benefits of social organization and for survival)
