PSY290H1 Chapter Notes - Chapter 2: Old World Rom, Genetic Recombination, Molecular Clock

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6 Oct 2012
Chapter 2: Evolution, Genetics, and Experience
Thinking about the biology of behaviour: from dichotomies of interactions
Zeitgeist: the general intellectual climate of our climate
Cartesian dualism: the idea that the human brain and the mind are separate entities
Is it inherited or is it learned?
Nature vs. Nurture
Most psychologists are committed to the nurture part of n v. n
John B. Watson, the father of behaviourism, states that there is no real evidence of the
behavioural traits
This started experimental psychology taking root in North America
But in Europe, this was around when ethology emerged: the study of animal behaviour
in nature
European ethology focused on instinctive behaviours, unlike North American
This emphasised the role of nature in behavioural development
Nature vs. Nurture (physiological -or -psychological) criticisms:
Many demonstrations show that even the most complex psychological changes can
be produced by damage to, or stimulation of, the brain
The man who fell out of bed:
Oliver Sacks is a patient suffering from asomatognosia (a deficiency in the
awareness of parts of one’s own body)
Usually consists of the left side of the body due to damage to the right
parietal lobe
Some nonhuman species, particularly primate species, have abilities that were
thought to be confined to the human mind.
The case of chimps in mirrors:
G. G. Gallup’s research on self-awareness in chimpanzees shows that chimps
show self-awareness.
Neural development
Neurons become active long before they are fully developed
The subsequent course of their development (if they survive, number of
connections, etc.) depends greatly on their activity, much of which is triggered by
external experience
Experience continuously modifies genetic expression
Behaviour is a product of three factors:
1. Genetic endowment (a product of evolution)
2. Experience
3. Perception of the current situation
Part 1: Human Evolution
Darwin’s theory of evolution:
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Not the first to propose that we evolve (undergo gradual orderly change), but first with
lots of supporting evidence. 3 main kinds of arguments:
1. Documented evolution of fossil records through progressively more recent
geological layers
2. Described striking structural similarities among living species, suggesting that we
evolved from a common ancestor
3. Pointed out the changes in animal and plants over selective breeding
Most importantly, he observed and tracked the evolution of finches on the Galapagos
Natural selection- the heritable traits that are associated with high rates of survival and
reproduction are the most likely to be passed on to future generations
Fitness- the ability of an organism to survive and contribute its genes to the next
Scientific theory- an explanation that provides the best current account of some
phenomenon based on the available evidence
Social Dominance
The males of many species establish a stable hierarchy of social dominance through
combative encounters with other males
This is important so that the dominant males are the ones that pass down their
genes to contribute to a stronger offspring than the lower-ranking males would
Courtship Display
Thought to promote the evolution of new species
Species: a group of organisms that is reproductively isolated from other
A new species can be formed by geographic isolation
But, a species can also form via a behavioural barrier, such as differing courtship
Course of Human Evolution
Evolution of Vertebrates
Complex multi-cellular water-dwelling organisms appeared 600 million years
(my) ago (mya)
About 150my later, chordates evolved
Chordate- animals with dorsal nerve cells (large nerves that run along the
centre of the back, or dorsum)
25my later, chordates with spinal bones to protect their dorsal nerve cords
evolved, called vertebrates
First, there were only primitive bony fish, then 7 classes of vertebrates:
3 classes of fish
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Amphibians (frogs, toads, salamanders)
410mya fish ventured out of water
400mya fins and gills evolved into legs and lungs to make the first amphibians
Amphibians must stay in water during larval form; only adults can survive on
Reptiles (lizards, snakes, turtles)
300mya the first reptiles evolved from amphibians
First vertebrates to lay shell-covered eggs and be covered in dry scales
Can live its whole life out of water, but spend the first stage of life in a watery
Scales help reduce water loss to allow terrestrial life
180mya, in the height of the dinosaurs, mammals evolved
The females feed their young with mammary glands and eventually stopped
laying eggs to nurture the young in a water environment within the body
There are 20 orders of mammals, we belong to the primate order
Apes (gibbons, orangutans, gorillas, and chimpanzees)
Evolved from a line of Old-World monkeys
Have long arms, grasping hind feet specialised for arboreal travel
Opposable thumbs
Emergence of Humankind
Of the family hominins which has two genera: Australopithecus and Homo
Believed to evolve 6mya in Africa from a line of apes
Homo has 2 species: Homo erectus (extinct) and Homo sapiens (us)
Thought to evolve from Australopithecus 2mya
Then we came along, Homo sapiens: Large brain, upright posture,
and free hands with opposable thumbs
Some evolution terminology:
Exaptations- evolved to form one function and were co-opted to form another
I.e.- bird wings; evolved initially with the purpose of walking
Homologous-structures similar due to evolutionary origin
Analogous- structures similar without evolutionary origin due to convergent
evolution (similar evolution in unrelated species due to environmental similarities)
Evolution of the Human Brain
The idea that the size of the brain is related to intelligence ran into two problems:
1. Humans are considered the most intelligent species but don’t have the largest
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