Samenvatting
Lecture 1 (Chapter 1)
Evolutionary psychology: the study of human mind and behavior from an evolutionary perspective
Using evolutionary theory to understand why the human mind works this way and how it has
been designed.
In effect, it means viewing humans as part of the animal kingdom, subject to the same laws
of evolution, natural selection, etc. in the primate tree of life
History of evolution:
Greek philosophers (600-400 BC) Aristoteles (300 BC) Medieval Christianity (16th
century)
Lamarck (18th century)
Darwin (19th century)
Mendel (19th century)
DNA discovery and the Modern Synthesis in Biology (20th century): 1.
function (evolution) and 2. mechanism (gene)
Jean-Baptiste Lamarck (18th century) driven by inner “needs”
1. Characteristics acquired through live can be given to offspring
2. Use and disuse of traits (e.g., muscles)
not true
Charles Darwin (1809-1882)
The voyage of the Beagle (1831- 1836) Book “On the Origin of Species” (1859)
Darwin quote: “As many more individuals of each species are born than can possibly survive;
and as, consequently, there is a frequently recurring struggle for existence, it follows that any
being, if it vary however slightly in any manner profitable to itself, under the complex and
sometimes varying conditions of life, will have a better chance of surviving, and thus be
naturally selected. From the strong principle of inheritance, any selected variety will tend to
propagate its new and modified form.”
Darwin’s theory made is possible to located humans in the primate tree of life and showing
our place in nature and links with other living creatures
Humans have a common ancestor with the apes
Three components of natural selection:
Variation: There is individual variation in traits (e.g. fighting ability, bone mass etc)
- Some trait variants have advantages that allow them to better compete for resources
Inheritance : If these traits are inheritable then they are passed on from generation to
generation
Selection: Organisms with heritable characteristics that are good for survival or reproduction
are more likely to reproduce more, and therefore out-produce the others
Result: individuals of a species become better adapted to their environments.
Gregor Mendel (1822-1884): missing piece for Darwin’s theory
Gene: the smallest discrete unit that is inherited by offspring intact, without being broken up
or blended. Half father half mother (Sometimes mutation, mutations with better advantages
causes adaptions over time)
Found out that there are recessive and dominant genes.
,Darwin: “The sight of a feather in a peacock’s tail, whenever I gaze at it makes me sick!”:
The plumage of the peacock was contradicting the natural selection theory because the
plumage was not good for survival and could attract more predators. Also for some species
there was a big difference between the sexes (size and structure), but they must have been
faced with the same problems of survival (eating, predators, diseases etc)
to explains this Darwin came up with the sexual selection theory:
Focuses on adaptations arisen as a consequence of successful mating
Two forms of sexual selection:
Inter sexual competition: traits that are passed on because they are good at attracting
opposite sex mates. For example: pretty feathers of birds
Intra sexual competition: traits that are passed on because they are good at winning same
sex competitions for mates. For example: ability to win fights to gain territory or resources
(status) desired by woman (traits: strongest/ biggest)
Physical attractiveness is high likely a product of sexual
selection, so as intelligence might be (if that is a quality that
attracts the opposite sex – inter sexual competition)
Humans are the product of evolution Incredibly
complex: Muscles, veins, organs, bones.
Not perfect, but functionally adapted to certain
environment! What environment?
The savannah hypothesis:
The environment where we evolved (we moved out
from the jungle to the savannah in Africa)
large animals (more meat), more vegetation, better
tree’s to protect the skin.
Walking upright was a advantages (could see further prey and enemies).
The most complex organ of all: the human brain
Triune Brain (Maclean, 1960).
Illustrative….
Reptilian brain, brain stem (avoid and approach)
Paleo-mammalian complex, limbic system (emotions)
Neo-mammalian complex, neo cortex (planning)
the brain is also a product of natural selection (got bigger and bigger)
What factors drove the increase in the hominid brain size? Theories:
Ecological factors (e.g. climate) needed to adapt to the climate (need to change food
when the climate changes)
Technology as we started hunting new animals we needed more advanced tools
Social factors living in larger groups or defending territories
Cultural factors learning better from each other
Out of Africa migration: modern humans exist from almost 60k years ago
Why did the Neanderthals go extinct, or did they?
They extinct nearly 30 thousand years ago, de reason why is a bit uncertain. According to the Out Of
Africa theory, the homo sapiens did evolve in Africa and then migrate to Asia and Europa. How this
exactly caused the rapid extinction of the Neanderthals is unknown. It is possible that they:
1. killed the Neanderthals
, 2. out-reproduced them (because they were better organized)
3. That they have been mixed (have common DNA with the Neanderthals).
The moment when Neanderthals went extinct can be determined due to the fact that homo sapiens
had a different shape chin and forehead, smaller brain size and softer bones.
Evolution is not a theory but a fact!
The earth is really, really old (~4,5 billion years)
DNA evidence shows that all living organisms are of common descent
Evidence for intermediate life forms (eg., feathered dinosaurs)
Evidence for natural selection in action (peppered moth evolution of the moth within the
last century)
History of evolutionary psychology:
Sigmund Freud: “sex is important!” (was wrong on some parts)
William James: “we have lots of instincts!” (overestimated)
Skinner’s Behaviorism: “anything can be learned as long as it is rewarded!”
- Radical behaviorism: a principle says that behavior followed by reinforcement leads to
repetition in the future, but that behavior followed by consequences (punishment)
would not be repeated in the future however further research contradict with this
principle.
Harlow and Garcia-experiments cause of the decline of the behaviorism of skinner
- Harlow raised two monkeys in a lab and discovered that in situations like fear the
monkeys would go to the mother which gave them comfort, not food (reinforcement)
- Garcia showed that rats are ‘programmed’ into this world to learn specific things, cannot
learn everything
- We learn some things easily but some things not at all. The roll of the mind and brain of
organisms must be taking into account when explaining behavior
E.O. Wilson (1975): The new synthesis: it examined species from ants to humans,
proclaiming that the same fundamental explanatory principles could be applied to all.
gave allot resistance
Richard Dawkins (1976): humans are basically nothing more than survival machines for genes
(genes makes bodies and brain to reproduce those genes)
Cosmides and Tooby (1992):
- The adapted mind: The brain is a swiss army knife (we have different tools that are
designed for specific tasks through evolution)
- They made assumptions on how humans work based on evolution
Theory by W.D. Hamilton (Inclusive-fitness “gene’s eye thinking”): If you are a gene you would first
make sure you can survive and then reproduce. But then you would also like to help other organisms
that carry a copy of your gene’s (relatives) to reproduce.
‘Adaptation and Natural selection’ by George Williams lead to the downfall of group selection and it
promoted the inclusive-fitness revolution.
Last six procedures for identifying adaptive problems:
1. Archeological records example: injury, deceases and death in the past and how they have
been adapted to several problems
2. Data form hunter-gatherer societies isolated from western civilization gives us
information about the problems our ancestors faced
3. Observations example: men got in more fights if there wife was fertile than if she was not
4. Self-reports example: difference in sexual fantasies between the sexes
, 5. Life-history data and public records Marriages, divorces, births and deaths are all part of
the public record, many hypothesis can be tested with these data
6. Human products fast-food exploit our preference is sugar and fat food. Reveal the design
of our evolved minds .
Misunderstandings about evolutionary psychology:
1. Human behavior is genetically determined…
- behavior cannot occur without two ingredients: (1) evolved adaptations and (2)
environmental input that triggers the development and activation of these adaptations
2. If it is evolutionary, we cannot change it…
- Example: Men have lower thresholds for inferring sexual intent when a woman smiles at
them, this is most likely based on an adaptation that motivates men to seek for sexual
opportunities. But knowing this can help men to reduce the number of times they act on
that ‘possible’ sexual interest.
3. Adaptations are optimally designed…
- Evolutionary time lags: Adaptation to new environments requires hundreds/thousands of
new generations. Example that we are not optimally designed: We have a strong taste
preference for fat and sugar That adaptive helped us in the past environment of scarce
food resources now causes diabetes and heart attacks.
4. It’s an adaptation so it must be good…
- No, an adaptation is formed in a specific time when our ancestors faced a specific problem
does not mean that it is good/ helpful in our current environment
Lecture 2 (chapter 2&3)
, Evolution has three products:
Adaptations: inherited characteristics that are naturally selected because they increase the
chance of survival and reproduction.
- Still functional: parenting (take care of babies until they are able to reproduce)
- Mismatched: Used to be adaptive but not anymore (preference for sweet and sugar)
By-products: carried along with adaptions but without a function (e.g. Belly button is a by-
rpoduct of the navelstreng)
Noise: random product with no function (Eye color)
- produced by forces such as mutations, sudden changes in environment, or accidents during
development
Problems with its adaptations and result:
Problem Adaptation Result
Handle objects Flexible thumb Grasping
Spotting game Two legs Seeing farther
Get ripe fruit from trees Color vision Find ripe fruit
Kids need to survive Care for kids Enhance survival of kids
You are vulnerable Group living Together you can do much more
Find a good mate like attractive mate (healhy, muscular) better genetic quality offspring
Snakes kill Being afraid Getting bites less
Group may abandon you Conform group Avoid social exclusion
Psychological adaptations: are evolved psychological mechanisms or if-then decision rules (if I see
something, then I must do this)
Solves a problem related to survival or reproduction
Takes in specific inputs and transforms it into adaptive outputs (solution to a specific
adaptive problem)
Outputs can be physiological, psychological, behavioural or combinations
Example: (input) see an angry rival – (transported through decision rules “if”, “then”
procedures) is he smaller of larger – (output) fight is he looks weaker or flee is he looks stronger.
Evolutionary psychology: Distinguish the Proximate from the Ultimate causes of this behavior
From what happened milliseconds ago to what happened millions of years ago
Infant crying:
Proximate explanations: Baby is cold, Is hungry, Mum leaves room
Ultimate explanations: Elicits care and defensiveness from mothers and other caregivers, which will
increase the likelihood of survival and hence lead to fitness benefits.
How to generate (and test) an evolutionary hypothesis? Two strategies:
Bottom up (inductive): Observation and then explain from theory
Top down: Starts with a theory and then form a hypothesis
Sexual selection hypothesis: Men show off their physical strength more in the presence of women
How would you test this?
Field study: observe male behavior in bar or gym when there are more women present
Lab study: present female faces on screen (vs. male faces) and have men do a competitive
task with each other
Cultural study: see if physically stronger men have a younger/more attractive wife in various
cultures
Research methods evolutionary psychology:
1. Compare different species example: Cliff- vs non cliffdwelling goats on orientation abilities
