Evolutionary psychology
Chapter 1
The three essential ingredients for natural selection
Most theories don’t account for the fact that organisms are beautiful adapted to their habitats, for
example the catastrophism theory that says that’s every era is ended by a catastrophe like a meteor
and then the world is reshaped with new species.
Darwin’s natural selection theory is based on three ingredients:
Variation: Every organism is different on various aspects, like fighting ability, defensive
ability, bone mass, wing length etc. This provides the “raw materials” for evolution
Inheritance: Only some of the variations are passed down to new generations, only these
variations play a role in the evolutionary process. Individuals with a certain trait survive and
reproduce at higher rates than others
Differential reproductive success: Organisms with heritable characteristics that are good for
survival or reproduction are more likely to reproduce more. For example birds that better
able to crack nut are more likely to life longer and thus can reproduce more.
Focusses on adaptations arisen as a consequence of survival (ex. Giraffe with longer necks
have a greater chance of surviving and thus reproducing and passing on the slightly longer
necks to the new generation)
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
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
Intrasexual competition: Competition of the same sex battle against each other for territory
or resources The winner has the best survival characteristics (Ex: strongest/biggest size)
desired by woman and therefore more likely to mate and reproduce
Intersexual selection: When member of one sex can select there mating partner on specific
quantities, those with these qualities more likely chosen to mate. Females choice (are more
choosy about whom to mate with), for example prefer someone who can provide her food
and gifts over time this cause an increase in males with the ability to provide food and
gifts.
Another process that can cause evolutionary change is called genetic drift: random changes in the
genetic makeup of a population through Mutation/ founder effects (if a group of 100 people colonize
a island and the groups includes 10 redheads, the percentage redheads in the groups over time will
be much higher than in the population where the group is originally from) / genetic bottlenecks (after
for instance due to a earthquake a large part of the population dies, the survivors carry only a part of
the original genes of the population)
Gene: the smallest discrete unit that is inherited by offspring intact, without being broken up or
blended
Genotype: the entire collection of genes within an individual, the offspring gets a random half of the
fathers and mothers genotype
,Define particulate inheritance
Gene: the smallest discrete unit that is inherited by offspring intact, without being broken up or
blended (Gregor Mendel) missing piece for Darwin’s theory
Genotype: the entire collection of genes within an individual, the offspring inherits a random half of
the fathers and mothers genotype the specific half of the genes we inherit from each parent is
identical to half of those possessed by that parent because they get transmitted without modification
(being broken up or being blended)
Inclusive-fitness “gene’s eye thinking” (theory by W.D. Hamilton): 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.
List three common misunderstandings about evolutionary theory
1. Human behavior is genetically determined (genetic-determinism)
Evolutionary theory represents a framework where human 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’s evolutionary, we cannot change it
Some things can be explained by evolution. However more knowledge about our evolved psychology
gives us more power to 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. although this knowledge can help men to reduce the number of times
they act on that ‘possible’ sexual interest.
3. Current mechanisms are optimally designed
(1) 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.
(2) Cost of adaptations: Some adaptations have a higher cost then benefit. Almost everyone is
afraid of snakes and spiders and that reduces the number of bites and deaths, but it is not
preferable because it doesn’t help us gathering fruits and plants necessary for survival.
4. Identify when Neanderthals went extinct
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 killed the Neanderthals, out-
reproduced them (because they were better organized) or that they have been mixed.
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.
5. Explain why radical behaviorism (Skinner) went into scientific decline
Radical behaviorism is 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.
The decline of the behaviorism is partly due to the research of Harry Harlow and John Garcia. 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, like if they eat food and then become sick, they
,won’t eat it again. The same principle accounts for humans. 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.
Chapter 2
examination of the four levels of analysis, going from most general to most specific: general
evolutionary theory, middle-level evolutionary theories, specific evolutionary hypotheses, and
specific predictions about empirical phenomena derived from these hypotheses.
"top-down" strategy: start with a theory and then form a hypothesis.
“buttom-up” strategy: start with a empirical observation and then try to explain it with a theory
Describe the three products of evolution.
Adaptation: Inherited and reliably developing characteristics that came into existence through
natural selection because they helped to solve problems of survival or reproduction better than
alternative designs existing in the population during the period of their evolution. must be a
characteristic of most or all members of a given species (exception: only at one sex)
- 4 requirements: Efficiency, economy, precision and reliability (Williams)
By-products: Characteristics that do not solve any problems, but are “carried along” with
adaptations who do. Example: Belly button, that is a by-product of the navelstren that transports
nutrients to the baby.
Noise/random effects: produced by forces such as mutations, sudden changes in environment, or
accidents during development. Example: shape of the belly button
EEA (environment of evolutionary adaptedness): the pressures that occurred during a specific period
that lead to specific adaptations.
Define the concept of “evolved psychological mechanism.”
Adaptations that make up the human mind, it is a set of processes inside an organism with the
following properties:
1. An evolved psychological mechanism exists in the front that it does because it solved a
specific problem of survival or reproduction recurrently over evolutionary history.
2. An evolved psychological mechanism is designed to take in only a narrow slice of
information. Example: eyes, only see in the visible spectrum and are designed to see specific
information.
3. The input of an evolved psychological mechanism tells an organism the particular adaptive
problem it is facing. For example when sniffing/ smelling food it unconsciously activate the
food-selection mechanisms (rotten vs sweet)
4. The input of an evolved psychological mechanism is transformed through decision rules or
procedures into output. 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.
5. The output of an evolved psychological mechanism can be physiological activity, information
to other psychological mechanisms, or manifest behavior. Example: seeing a snake you
can get physiological frightened, use this information for behavior options such as freezing or
use this information for action, such as running away (behavior output)
, 6. The output of an evolved psychological mechanism is directed toward the solution to a
specific adaptive problem.
In summary, an evolved psychological mechanism is a set of procedures within the organism
designed to take in a particular slice of information and transform that information via decision rules
into output that historically has helped with the solution to an adaptive problem. Psychological
mechanisms exist in current organisms because they led, on average, to successful solutions to
specific adaptive problems for that organism's ancestors
List nine methods for testing evolutionary hypotheses.
1. Compare different species example: Cliff-dwelling goats vs non-cliff-dwelling goats to test
if cliff-dwelling goats have better spatial orientation abilities
2. Cross-cultural methods Most obvious method for adaptations that seems to be universal
like basic emotions, also a good method to compete hypothesis against each other.
3. Physiological and brain imaging methods example: stepchildren have a higher level of
cortisol than nonstepchildren, and would thuss experience more stress. Imaging is also a
good method to test hypothesis and their underlying neural basis like jealousy.
4. Genetic Methods Twin studies and adoption studies can be used to test evolutionary
hypothesis. Example: Female children will ovulate soner if there is no investing father
around. Example molecular genetic method: test hypothesis about the modern human
origins out of Africa and to see if there have been any adaptations (there has)
5. Compare males and females comparing the different problems faced by males and
females. Example: men’s jealousy is especially triggered by infidelity (ontrouw) because
woman always know that they are the mother and men don’t.
6. Comparing individuals within a species example: rich vs poor, old vs young etc
7. Comparing the same individuals in different context example: teaching a men how to hunt
properly leads to a higher status and therefor attracted more sex partners, respect and self-
esteem. hard to determine the controlling factors due to the fact that a lot of things
happen at the same time
8. Experimental method example: different groups to different situation to test hypothesis
9. Evolutionary computer simulations Helps to predict and to verify/ seek for flaws in a
research outcome, get to know what to run next on the computer.
Identify seven data sources for testing evolutionary hypothesis.
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
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 .
7. Transcending the limitations of single data sources combining multiple data sources who
don’t have the same limitations is really powerfull
Last six procedures for identifying adaptive problems.
1. Guidance from modern evolution theory