Lecture 1: foundations of evolutionary psychology
A short overview of evolutionary psychology
Evolutionary psychology is the study of human behaviour, affect and cognition from an evolutionary
perspective. Using evolutionary theory to understand why the human mind works this way and how
it has been designed. In effect, this means viewing humans as part of the animal kingdom, subject to
the same laws of evolution, natural selection, etc. Every species has its own nature. Evolutionary
psychology focusses on four key questions:
1. why is the mind designed the way it is?
2. How is the human mind designed?
3. What are the functions of the component parts and their organized structure?
4. How does input from the current environment interact with the design of the human mind
to produce observable behavior?
Jean-Baptiste Lamarck (1744-1829)
1. The inheritance of acquired characteristics
2. Use and disuse of traits (for example muscles)
Evolution
We receive our set of genes from our parents, and they from their parents, and so on. Because of
this the genome is shaped by evolution over the years, this is also known as Darwin’s evolution
theory. Darwin hypothesized that all modern organisms are descended from a small set of shared
ancestors, and that they have merged over time through the process of evolution. The key
mechanism of evolution is natural selection, which happens under three conditions:
- There is variation among individuals of a population
- Individuals with a certain trait survive, and reproduce at a higher rate than other
- The trait associated with this advantage is passed from parents to offspring
Because of natural selection specific traits will be better represented in the next generation. The
evidence for the modern evolutionary theory comes from many sources:
- The fossil records
- The resemblance between genomes of various organisms
- Pseudogenes
- Distributions of species around the world
This evidence, however, does not follow that evolution somehow improves organisms and can only
lead to rigid behavioural patterns.
Sexual selection
There are two forms of sexual selection
- Inter sexual competition: traits that are passed on because they are good at attracting
opposite sex mates (pretty bird feathers)
- Intra sexual competition: traits that are passed on because they are good at winning same
sex competitions for mates (stag fights)
Humans are the product of evolution
Humans are the products of evolution; they are incredibly complex organisms. Humans have
muscles, veins, organs, and bones, which we have because of evolution. Humans are not perfect, but
they are functionally adapted to a certain environment. The savannah hypothesis: human
bipedalism evolved as a direct result of human’s ancestor’ transition from an arboreal lifestyle to
one on the savannas.
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,The human brain
The most complex organ of all is the human brain. The human brain has evolved from a small brain
to a bigger brain over the years. Factors driving the increase in the hominid brain size:
- Ecological factors
- Technology
- Social factors
- Cultural factors
Evolution has three products:
- Adaptions: inherited characteristics that are naturally selected because they helped to solve
a problem of survival or reproduction
- By-products: carried along with adaptions without function (belly button)
- Noise: random effects, no importance (eye color)
- Mismatched adaptions: used to be adaptions but not anymore (preference for sweet, fatty
foods)
Biologically innate Culturally acquired
Language capacity English, Dutch, sign language
Desire to eat food Taste for pizza, sushi
Desire for social status Money, strength, publications
Desire to be attractive Slim, voluptuous, tie, penis sheath
Misunderstandings about evolutionary psychology
1. Human behaviour is genetically determined… environments and learning matter too
2. If it is evolutionary, we cannot change it… no, we can shape our own future
3. Adaptions are optimally designed… not always in new environments
4. It is an adaption, so it must be good… no, what is, is not what ought (natural fallacy)
The extinction of Neanderthals
- Anatomical evidence: The Neanderthals went extinct because homo sapiens and the
Neanderthals differed dramatically anatomically. These large anatomic differences suggest
that Neanderthals and early modern humans were isolated from each other, rather than
mating with each other and possibly evolved into two somewhat distinct species.
- Archeological evidence: about 100,000 years ago Neanderthals and homo sapiens were
quite similar. Both had stone tools but lacked tools of bone, ivory, or antler; hunting was
limited to less dangerous species. Then, 40,000 to 50,000 years ago a massive
transformation occurred (creative explosion). Tools became varied, but the Neanderthals did
not partake. Creative explosion might have occurred due to a new brain adaption.
The broad classes of adaptive problems
1. Problems of survival and growth
2. Problems of mating
3. Problems of parenting
4. Problems of aiding genetic relatives
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, Lecture 2: adaptions for survival
Evolution is not a theory but a fact
Our earth is old, about 4,5 billion years. DNA evidence shows that all living organisms are of
common descent:
- Evidence for intermediate life forms feathered dinosaurs
- Evidence for natural selection in action peppered moth
History of evolutionary psychology
- Sigmund Freud: sex is important
- William James: we have lots of instincts
- Skinner’s behaviourism: anything can be learned as long as it is rewarded!
- End of behaviourism? Garcia and Harlow-experiments
Evolution has three products
- Adaptions: inherited characteristics that are naturally selected because they helped
humans solve a problem of survival or reproduction
o Still functional: parenting
o Mismatched: used to be adaptive, but isn’t anymore
- By-products: carried along with adaptions but without function (belly button)
- Noise: random effects that have no function (eye colour, musical taste)
What are psychological adaptions?
Adaptive problems and their solutions (adaptations)
Problem Adaption Result
Handle objects Flexible thumb Grasping
Spotting game Two legs Seeing further
You are vulnerable Group living Together more can be done
Group may abandon you Conform to group Avoid social exclusion
Psychological adaptions are evolved psychological mechanisms or if then decision rules:
- They solve a problem related to survival or reproduction
- Takes in specific inputs
- Transforms it into adaptive outputs
- Outputs can be physiological, psychological, behavioural, or combinations
Types of psychological causes:
- Proximate cause: a proximate cause in an immediate, mechanical cause on a trait:
for example, the influence on day length on the concentration of a hormone in the
bird’s brain.
o Proximate explanation of crying baby:
Baby is cold
Baby is hungry
Mother leaves the room
- Ultimate causes: an ultimate cause is a historical explanation explaining why an
organism has one trait rather than another, often in terms of natural selection.
o Ultimate explanation of baby crying:
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