Lecture 29: Evolution of the nervous system Flashcards
In what ways do brains differ between animals?
overall size -> birds, mammals and cartilaginous fish have increased relative brain size
relative regional size increases -> esp. neocortical scaling
brain architecture design -> esp. neocortical parcellation
What is important for brain architecture design?
lamination, migration, segregation and mappings
What hasn’t changed in the brain between animals?
thickness of the cerebral cortex
What makes the brains of primates different to most other animals?
bigger brains (in relation to body size)
more neocortex
more distinct architectures in the neocortex
Is size the only difference between the chimpanzee and the human brain?
no, there is also a parcellation difference
What is the language area in humans?
Broca’s area (44 and 45)
What might be more indicative of evolutionary changes in the brain compared to other organs?
patterns of gene expression rather than genomic homology
What does the distance between any two species indicate?
how different they are in the pattern of gene expression
What is the variation in gene expression doing (between humans and other animals)?
human brains not only have a greater proportion of pfc, they seem to have a lot more variety of gene expression in pfc, and a lot more pfc white matter, and pfc connectivity
How were Australopithecus sediba different to modern humans?
brain volume about 420cc (small brain)
wider pelvis
maybe more frontal cortex
What has been considered a driver of evolutionary change towards intelligence?
the evolution of grassland i.e. freeing the forelimbs to allow hands to make tools
What suggests that freed hands wasn’t a trigger for cerebral expansion?
brain size increased well after bipedalism
bipeds existed for two million, or even several million years before brains got bigger than chimp-sized
What does the Variability Selection Hypothesis propose?
that relatively rapid environmental change replaced habitat-specific adaptations and favored adaptations that increased the ability to respond and accommodate this change (such as increased intelligence and greater social complexity)
What are the costs of having a big brain?
need long gestation and long parental care = huge burden
big head = difficult birth
complexity = more genes, more mutations
large energy expenditure / heat production
What are the pressures that promote bigger brains?
benefits of social organisation
survival enhanced by being smarter (tools, clothes, hunting / gathering)
