Lecture 17 - Evolution of a cognitive brain Flashcards
What is meant by evolution?
Species change over time.
But not all species change a lot. Some are highly successful and stay
almost the same for millions of years (e.g. sharks)
Why do some change a lot?…. Because their environment either changes, or is more competitive (or both)
How do species change?
Through Natural Selection
“survival of the fittest” – what kind of fitness?
There is no absolute definition of ‘fittest’
Fit to the environment….and environments change
Darwin was inspired by artificial selection…what farmers do when
breeding livestock
(the farm and farmer is the ‘environment’ for livestock; the individuals that best fit
the farm, e.g. by producing more milk or being more docile, get to breed most).
Shift in genes and black death
One gene-variant seems to have given people 40% better chance of surviving
(it codes for a protein that is good at chopping up invading microbes).
Relative advantage depends on the current environment – today that same
gene-variant is associated with higher risk of auto-immune diseases.
There was a 10% shift in its prevalence over 2-3 generations, and it remains
more common today than before the black death.
Huge shift in short amount of time
No definition of good or best, depends on environment. In some cases this gene good in others higher risk of autoimmune disease
What does natural selection mean?
Natural selection simply means that those individuals with most surviving
offspring have a stronger genetic influence on the next generations
Natural selection can’t see the future or act for whole species.
Each small change conferred an advantage to individuals in the
environment they were in at the time.
What are key ingredients for natural selection?
What are the key contributors to having successful offspring?
Key ingredients:
1. variation – individuals differ (otherwise next
generation will be the same no matter what)
2. competition – number and success of offspring varies
(so that the genes from some individuals are more represented in the
next generations).
What is the lecture outline?
Evolution and our family tree
Natural selection
Primates: visuo-motor expansion
Brain functions from an evolutionary perspective
case study
1: colour vision
Apes: expansion of ‘association cortex’
Brain functions from an evolutionary perspective
case study
2: Memory
Primates part of lecture
Who has lots of neocortex?
Humans, chimps and monkeys
carnivores have quite a lot of neocortex
Mice and rats (which are one of our closest relatives) do not have much neocortex so this expansion happened when we split from rodents
Whales have quite a bit of neocortex
Direct correlation between social complexity and neocortex. Online also says intelligence. He thinks probably came about for better sensory processing
Brain functions from an evolutionary perspective
Primate sensory systems are somewhat different from mammals
Compared to most mammals we reply much more on sight than smell and hearing
Primate visual cortex is relatively huge
One example of change: one type of colour vison has evolved
Primates have bucked the trend and re-invented trichromacy (3 dimensional colour vision)
Why might primates have developed this 3 dimensional colour vision?
Likely an advantage for finding fruit in foliage
Other mammals do not rely on this job to process fruit and so they have optimised their vision for other things - such as being sensitive in the dark
Part of the lecture about Apes: expansion of ‘association cortex’
Fun fact about cerebral cortex
The last common ancestor of monkeys and humans probably had ~1.5 million neurons in its cerebral cortex. We have about 16 billion.
Brain could have developed and changed like any other part
Memory systems: case study
How does episodic memory come about?
Hypothesis- comes from navigation. You have a memory for where you have been and this supports episodic memory
Hippocampus supports navigation abilities, HM case study shows episodic memory supported by the temporal lobe, how did one situation lead to another?
Navigational representation guided fish through their environments and they remembered the routes consciously and unconsciously and what the advantages of going different routes were and this would develop into representation of past activity and my past.
Another idea - social cohesion - representations of the self (which comes from knowing the past) initially prompted social cohesion came to underlie the sense of owning knowledge and participating in events, real and imagined.
Where has the expansion in the brain mostly been relative to monkeys?
The temporal lobe, the parietal lobe and the frontal lobe. These are ones that do the more conceptual tasks away from the directly motor (such as language).
Brain takes 20% of our food.
Weird stuff about humans
Obvious solution to small hips big brains and deaths in childbirth is smaller skulls - less deaths in childbirth. Babies need to be born 6 months or would not get out as big brain but ideally due to helplessness need 15 months.
Other weird stuff is menopause.
Why some areas of brain dedicated to certain areas?
Lateralisation not unique to humans. We have it because ancient mammals did. Why? Feeding vs alerting - it helped to specialise focused attention ie to food to other stuff. When we developed language it came out of a lateralisation plan not equally distributed. Language is lateralised accross the brain.
We are born with ability to want to learn language.
Example questions from this lecture
- Evolution is best conceptualised as
a) A ladder progressing from primitive to advanced animals
b) A branching tree where today’s animals are the twigs and ancestral
species are the branches.
c) A bush, where the roots are all the animals that combined to make us
d) A daffodil. - In the famous example of Galapagos finches
a) Big beaks are the best
b) Small beaks are the best
c) The advantage of different beak sizes depends on the current conditions
d) Middle sized beaks are the best - For natural selection to change a population of animals over several generations there
must be both:
a) Variation and competition
b) Competition and consistency
c) Consistency and variation
d) None of the above
