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Psychology 4000
Evolutionary Psychology
Dr Darren Hannesson
„
Lecture 2
What is evolutionary psychology?
„ The theory of evolution by natural selection
„
„ natural selection
„
„
„
variation
inheritance
selection
„ objections to evolution
„
The modern synthesis: Evolution and genetics
„ mendelian genetics
„ genes and DNA
Updates to evolutionary theory
„ Misunderstandings about evolution
„
1
What is evolutionary psychology?
„
a sub-field of biopsychology
„
the study of behaviour and mind in terms of their underlying
biological mechanisms
„ genes, development, anatomy & physiology, evolution
What is evolutionary psychology?
„ Field of study = Subject matter (question) +
explanation (answer)
„ “the study of behavior
and mind in terms of their
function as solutions to adaptive problems faced
during human evolutionary history”
history”
„ “the study of human evolutionary history and how it
may have generated behavior and mind as solutions to
adaptive problems”
problems”
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What is evolutionary psychology?
Examples
„
Why do women show a preference for mating with
older men?
„
„
Explanation should be in terms of selective pressures
that could have made such a mating preference adaptive
during our species evolutionary history
What impact might hunting have had on human
psychology?
„
Explanation should be in terms of adaptive problems
that arose as a result of using hunting as an important
means of food acquisition and how current
psychological traits may have helped solve these
problems
The theory of evolution by natural
selection
„
evolution
„
„
change in species over time
emerged to explain to three fundamental observations
„
„
„
„
there are a wide variety of species on earth
the characteristics of each species are particularly suited to achieve
achieve
distinct functions
species share a remarkable number of structural and functional
characteristics
Lamarckian evolution
„
transmission of acquired characteristics
3
The theory of evolution by natural
selection
„
Charles Darwin
The theory of evolution by natural
selection
„
Darwin’
Darwin’s finches
4
The theory of evolution by natural
selection
„
principles of population
„ results in a struggle for existence
„ “winners”
winners” are those with favourable variations
„
repeated over generations this results in new species
The theory of evolution by natural
selection
„
3 key elements of Darwin’s theory
„ variation
„ inheritance
„ selection
5
The theory of evolution by natural
selection
„
currency of evolution is “differential reproductive
success”
„ do you produce more reproductive offspring than the
“Joneses”
Joneses”
„ what about survival?
The theory of evolution by natural
selection
„
objections to evolution
„
emotional
„
religious
„
rational
6
The modern synthesis of
evolutionary theory and genetics
„
genetics helps account for two aspects of
evolution:
„
heritability
„
variability
The modern synthesis of
evolutionary theory and genetics
„
Mendelian Genetics
„
Mendel’s pea experiments
(http://www2.edc.org/weblabs/Mendel/MendelMenu.html)
„ bred peas with seeds that were green or yellow
7
The modern synthesis of
evolutionary theory and genetics
„
Mendelian Genetics
„
Proposed particulate inheritance
„ genes
„
the unit of heredity
„
each person is made from a complete set human genes
„
each person has two copies of this set
The modern synthesis of
evolutionary theory and genetics
„
Mendelian Genetics
„ Dominant
vs recessive
„ Genotype vs phenotype
8
The modern synthesis of
evolutionary theory and genetics
„
Biochemistry of Genetics
„
genes are written in the language of a molecule:
„
DNA (deoxyribonucleic acid)
„
DNA is constructed from
„
„
„
„
Sugar backbone
Paired nucleotides
two strings of sugar backbones interlinked by cross matched base
pairs twisting in the form of a double helix
„ each molecule of DNA forms a complex with some proteins
and forms a chromosome
each species has a characteristic # of chromosomes
The modern synthesis of
evolutionary theory and genetics
„
The genetic code
„
genes do one of two things:
„
code for long strings of amino acids (structural genes) or
they regulate the function of other genes
„
the “code”
code” consists of a sequence of 3 base pairs (a codon)
„
„
sequence of codons serves as template for stringing amino acids
together to form proteins
„
„
Enzymes
Structural proteins
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The modern synthesis of
evolutionary theory and genetics
„
Inheritence
„
Meiosis generates gametes that contain one copy of
each chromosome
„
Contains 1 full set of genes
„
Offspring are created when one gamete is “fertilized”
fertilized” by the
opposite sex gamete creating a zygote with two sets of
chromosomes
„
Zygote has two copies of each gene
„ May be homozygous (same - yy)
yy) or heterozygous (different Yy)
Yy)
The modern synthesis of
evolutionary theory and genetics
„
Sources of variation
„
„
Sexual reproduction
„
Recombination
„
crossing over
„
meiotic errors
Mutation
„
„
mitotic errors
Environmental effects
„
Penetrance
„
PKU
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The modern synthesis of
evolutionary theory and genetics
„
Genes and gender
„
gender is determined by one pair of chromosomes called
sex chromosomes
„
XX Æ female; XY Æ male
all others are called autosomal chromosomes
„
sexsex-linked genes
„
„
„
genes on X chormosome will be apparent in different frequencies
in males and females
sexsex-limited genes
„
genes that have an effect on oneone-sex but not the other
Updates to evolutionary theory
„
sexual selection
„
natural selection emphasized adaptations that
promoted survival
„ some traits seem to decrease survival
„ traits that directly promoted reproductive success could
be highly adaptive
11
Updates to evolutionary theory
„
sexual selection
„
Intrasexual selection
„ traits that facilitate competition between members of the
same sex for access to mates
Updates to evolutionary theory
„
sexual selection
„
Intersexual selection
„ traits that promote being selected as a mate by the
opposite sex
12
Updates to evolutionary theory
„
Inclusive fitness
„
classical fitness = an individual’s reproductive success
„ BUT selection operates at
the level of the gene not the
individual
„
genes that promote their own survival/reproduction will be
selected for regardless of “who carries them”
them”
„ therefore …
„
inclusive fitness = classical fitness + effects on
survival/reproduction of kin (since they also carry many of your
genes)
Updates to evolutionary theory
„
Adaptations
„
solutions to specific problems that impacted reproductive success
„ Must be …
„
„
„
Reliably expressed
Efficient
Economical
13
Misunderstandings about evolution
„
Adaptations are strictly genetically
determined
„ Instead:
„
„
adaptations prepare response forms
responses are both elicited and shaped by the environment
Misunderstandings about evolution
„
Adaptations produce inflexible,
unmodifiable traits or behavior
„ Instead:
„
„
organisms alter their environment
organisms have a repertoire of adaptations
14
Misunderstandings about evolution
„
Adaptations should produce optimal designs
„
“why aren’t we perfect?”
„ Instead
„
several factors limit the likelihood of optimal designs
„ evolutionary lag time and environmental variation
„ costs
„ biological system constraints
Misunderstandings about evolution
„
Adaptations should produce optimal designs
„
“why aren’t we perfect?”
„ evolutionary lag time and environmental variation
15
Misunderstandings about evolution
„
Adaptations should produce optimal designs
„
“why aren’t we perfect?”
„ costs
Misunderstandings about evolution
„
Adaptations should produce optimal designs
„
“why aren’t we perfect?”
„ biological system constraints
16