lecture 6 - Brain Evolution

Question 1

what did Charles Darwin propose?

Answer 1

Evolution- natural selection, selectional pressures and adaptations.

Question 2

what must you have for successful evolution?

Answer 2

Extinction.

Question 3

how many known species are there?

Answer 3

2 million.

Question 4

what creates variation?

Answer 4

Mutations- unfavourable mutations are selected out and adaptive mutations are favoured then spread through the population.

Question 5

Define Homology.

Answer 5

Physical resembelence based on common ancestory.

Question 6

Give an example of Homology.

Answer 6

All mammalian forlimbs have commonly inherited characteristics.

Question 7

what is convergent evolution?

Answer 7

were 2 different species living in the same environment can produce the same characteristics, as selectional pressures are so similar to each other.

Question 8

give an example of convergent evolution.

Answer 8

A tuna fish and a dolphin resemble each other because they have evolved for efficient swimming. Even though a Tuna is a fish and a dolphin is a mammal.

Question 9

what is an analogous feature?

Answer 9

similarity of function although the structures of interest may look different. e.g. human hand and elephants trunk.

Question 10

how many years ago did humans evolve?

Answer 10

4-6million years ago.

Question 11

what is the FOXP2 gene?

Answer 11

the first gene relevant to the human ability to develop language.
The gene that enables us to speak- making humans unique.
A gene thought to be critically involved in vocal behaviour across species.

Question 12

what is the FoxP2 gene?

Answer 12

this is the mutation gene of FOXP2 that is involved in vocal behaviour.

Question 13

did Neandertals have the human variant of the FOXP2 gene?

Answer 13

yes

Question 14

what is the aim of the Neandertals Genome Project?

Answer 14

to characterise the DNA from fossils that are understood to be Neandertal in origin. To see if they too were capable of speech and language.

Question 15

what did Krause et al (2007) give evidence/support for in his experiment?

Answer 15

Neandertals are capable of speech/language as 46 DNA samples from 22 bones from 46000 were extracted and found to have the SAME mutations as humans today.

Question 16

how does the human brain compare with other species?

Answer 16

we have a large cranial capacity - space inside skull filled with the brain.

Question 17

what is the advantage of studying cranial capacity?

Answer 17

because it can also be applied to the fossilied remains of extinct species.

Question 18

what is linked to larger brain size?

Answer 18

mammals-tend to have larger brains as they eat food that are harder to find e.g ripe fruit.

Question 19

what did Jerison (1973) think about brain size?

Answer 19

normal for brains to get bigger if humans get bigger- not that surprising after all?

Question 20

what is the Encephalisation Quotient?

Answer 20

A measure of brain size relative to body size.
EQ = A/E
(ratio of species actual brain size to the expected given its body weight).

Question 21

how many times larger is the human brain than a hypothetical primate of the same body size?

Answer 21

3.

Question 22

what part of the brain has evolved more rapidly than other brain areas?

Answer 22

Cerebral Cortex - interesting as it develops later in life.

Question 23

what does Jerison think about brain size and cognitive capacity?

Answer 23

they must be RELATED.

Question 24

what does Holloway suggest?

Answer 24

evolutionary change takes place due to brain reorganisation NOT just the expansion of the same areas. Human brains are different in comparison to other primates.

Question 25

Encephalisation vs. Reorganisation- what 2 aspects are needed to examine this problem in the Cortex?

Answer 25

Micro architecture and Macro architecture.

Preuss (2001)

Question 26

what is micro architecture?

Answer 26

examination of neurons/networks/cortical columns/organisation. e.g Mountcastle -suggested that cortical columns are organised the SAME way throughout the brain in every species. Although other researchers have found differences accross species.

Question 27

what is Macro architecture?

Answer 27

examination of the size of existing/new cytoarchitecture/ Brodmann areas. asking the Q: same no. of cortical areas OR new cortical areas?

Question 28

what part of the brain has evolved selectively to give us sophisticated mechanisms like language/memory/ToM?

Answer 28

Frontal Cortex.

Question 29

what is the Machiavellian brain?

Answer 29

this is the social brain hypothesis! we need a bigger brain to interact with bigger social groups.

Question 30

what did Barton et al (1996) discover?

Answer 30

they found a relationship between the size of the neocortex and the size of groups that they lived in.

Question 31

Dunbar disagreed with Barton et al (1996) on the social brain, why?

Answer 31

not the size of the social group but the complexity of the relationships that are important.

Question 32

Explain Hill and Dunbars christmas card experiment.

Answer 32

firstly they took all other no-human primates neocortex ration first then predicted using this what the optimal group size would be for humans. they used the exchange of christmas cards to compare there social network.
REMARKABLY this was very close to the group size predicted for humans based on the size of there neocortex.

Question 33

what did Kudo and Dunbar (2001) note about primates grooming each other and brain size?

Answer 33

across a range of species: neocortex size varied with the sizes of grooming cliques.

Question 34

what did Byrn and Corp (2004) note about tactical deception and brain size?

Answer 34

tactical deception (deliberately misleading members of their group to achieve their goals) across different species scaled with neocortical size. this is a specific example of cognitive ability related to the social brain hypothesis.

Question 35

what did Semedeferi (1997) say there is nothing special about?

Answer 35

humans frontal cortex.

Question 36

what did Brodman disagree with Semedeferi for?

Answer 36

the prefrontal cortex (part of the frontal lobe) has selectively evolved.

Question 37

what is Barton and Harveys (2000) Mosaic Hypothesis of Brain Evolution?

Answer 37

individual brain areas DO NOT evolve independently - brain areas evolve together and similarly. Evidence: connections in the prefrontal cortex have expanded as there is more white matter.

Question 38

what evidence did Semendeferi and Passigham (2002) have to disagree with Schoenemann et als (2005) study on white matter?

Answer 38

used MRI scans as evidence which didnt reveal cytoarchitecture boundaries.

Question 39

Which areas of the cerebellar cortex would appear to be differentially evolved in the human brain compared to other non-human primates?

Answer 39

Crus I and Crus II, associated with learning cognitive skills.

Question 40

Evidence suggests that teeth of modern humans develop slower than earlier hominins. What does this suggest?

Answer 40

The period of juvenile development is prolonged in modern humans, increasing the opportunity for socialisation.