Brain Evolution

  • Created by: Yasmetron
  • Created on: 04-02-23 20:42
Define natural selection
Evolution is a change in genetic composition of a population over time. Gradual accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environments.
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How do mutations help?
Mutations create variation
Unfavourable mutations hamper reproduction and are selected out
Adaptive mutations are favoured and spread through the population
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Define homology
Homology: Common ancestry between species is revealed by common physical traits shared by these populations
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Define Genetics
Genetics: Advances in scientific techniques allows us to study similarities between species independently of homology
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What is convergent evolution?
– Similar environments can induce two relatively independent species to evolve similar homology
– Two genetically dissimilar species can have very similar homologies
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Who are we related to?
Cousins with chimpanzees - 5 million years ago
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What is the social brain hypothesis?
o Dunbar (1998)
o We need bigger brains to interact with bigger social groups
o Information processing demands should increase with the number of social relationships
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What is the relationship with neocortex and group size?
as volume of the neocortex increases so does the mean group size.
Out group size should be 150 – meaning we have the mental capacity to be able to deal with 150 people.
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What did Kudo and Dunbar (2001) find?
- Primates regularly ‘groom’ eachother – this is an important social activity that promotes bonding between members of the group.
– Grooming cliques vary with species
– Across a range of species, neocortex size (corrected for overall brain size) varied wi
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What did Byrn and Corp (2004) find?
– Tactical deception: Social primates often deliberately mislead members of their group to achieve their goals.
– The frequency of tactical deception across different species scaled with neocortical size.
– This is a specific example of a cognitive abilit
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Where has absolute brain size come from?
studying cranial capacity is that it can also be applied to the fossilised remains of extinct species
ince the same measure is used to obtain data from extant and extinct species, they can be directly compared.w
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What is relative brain size?
Brain size is known to scale with body size (the brain gets bigger only because the body gets bigger – so perhaps there is nothing special about the size of the human brain)
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What is the Encephalisation Quotient?
Encephalization quotient (EQ):
Ratio of a species’ actual brain size to the size expected given its body weight
Humans still have the largest EQ (6) relative to other primates primates.
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What did Holloway suggest?
Evolutionary change takes place through brain reorganisation – not simply by expansion of the same areas
He suggests that the brian of modern humans is qualitatively different from other primates and not just quantitatively bigger
Encephalisation Quotient
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What parts of the brain evolve quicker?
The trajectory of some brain areas including the neocortex is much faster than other brain areas.
The cerebral cortex has evolved more rapidly than other brain areas.
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Define micro architecture?
the organisation of the cortex on a small scales – neurons, networks, cortical column organisation etc
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Define macro architecture?
the organisation of the cortex on larger scales (the size of existing/new cytoarchitectonic/Brodmann areas etc.
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What is micro architecture?
• Mountcastles concept of cortical columns are organised in the same way throughout the brain in every species.
• Some report that these columns are highly conserved (almost the same number of neurons in every column in nearly all species). Input/output o
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What is macro architecture
Some have suggested that primates tend to have the same number of cortical areas
Others emphasise the evolution of new cortical areas (e.g.Allmann, Kaas, see Preuss reviews)
Frontal Cortex: There are good functional grounds for suggesting that the fronta
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Define mosaic evolution?
The idea that individual neural structures evolved independently of each other.
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Define concerted evolution?
Evolutionary pressures act not on individual brain structures, but on whole functional systems comprising several interconnected parts of the brain.
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What did Semendeferi (1997) suggest?
Semendeferi (1997): The frontal lobe occupies the same proportion of the cortex in most species: there is nothing special about the humans frontal cortex
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What are Schoenemann et al. (2005) study and find?
Used 46 structural MRI scans of 46 primates (11 species) – he found that we have a similar amount of grey and white matter, grey matter from different species however when you look at the white matter, there is a great difference between humans and other
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What did Semendeferi and Passingham argue?
MRI scans don’t reveal cytoarchitecture boundaries – prefrontal boundaries in Schoenemann seem to be arbitrary
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Other cards in this set

Card 2


How do mutations help?


Mutations create variation
Unfavourable mutations hamper reproduction and are selected out
Adaptive mutations are favoured and spread through the population

Card 3


Define homology


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Card 4


Define Genetics


Preview of the front of card 4

Card 5


What is convergent evolution?


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