Biologische Psychologie (jaar 2, blok 1)
Psychobiology (Chris
Chandler).pdf
Psychiobiology – Chris Chandler (2015)
Chapter 2. Genetics and Evolution
- Evolution
- Mechanisms of heritable traits
- Molecular genetics: DNA
- Behavioural genetics
Evolution
- Science <-> religion -> Pro-creationism: view that evolution is untrue and
humans+world were created by a superior being (God) -> God as the creator of all
challenged, e.g. by Dawkins
- Dawkins: transmission of genetic material is the meaning of life ->
"We are machines built by DNA (deoxyribonucleic acid) whose purpose is to make
more copies of the same DNA ... This is exactly what we are for. We are machines
for propagating DNA, and the propagation of DNA is a self-sustaining process. It is
every living object's sole reason for living."
- Darwin: orgin of the species, most influential, evidence-based approach
- Evolution: change in inherited characteristics over successive generations
- The theory of evolution: all organisms are related and share a common ancestor
-> modern organisms are (successful) adaptations of previous generations. These
modifications occur in the process of natural selection. Certain characteristics of
the organism are more beneficial within a particular environment. In a difficult,
demanding, or hostile environment, some characteristics will be to the organism's
advantage, others might be a disadvantage. Therefore those organisms that
possess beneficial characteristics are more likely to survive and reproduce
➔ Organisms with beneficial characteristics (can adapt best), will survive +
reproduce = natural selection/survival of the fittest (=organisms that ‘fit
- behavioural/cognital - into’ their environment are more successful at
survival)
- Survival of the fittest: the continuation of an organism that has successfully
adapted to the environment which means they live long enough to reproduce
Reproduction: production of offspring by sexual/asexual process -> passing
characteristics to the next generation, characteristics that don't fit well are less likely to
exist in successive generations (because those who possess them are more likely to die
without having the chance to have reproduced)
Natural selection: process by which characteristic of individual that allows it to survive to
produce offspring will continue in the species -> distinct from traditional selective
breeding programmes. It has no specific plan, environment is the influence + evolution is
relatively slow -> selective breeding of animals is specific + intentional act, producing
offspring with particular characteristics that were present in the parental generation (e.g.
racehorse breeds)
- Selective breeding: breeding animals+plants specifically to display a particular trait
, Genetic modification: quicker form, genes are added/deleted for the benefit of the
organism or if not the recipient organism, then at least mankind
Evidence - Evolution via natural selection
1. Biogeography
- Environment -> e.g. temperature
- Organisms are the best fit for their unique environment
- Hard to study, takes long
- Rapid changes cuz of selective breeding
- E.g. Dry island→only large seeds→birds with large beaks
survive+reproduce=characteristic large beak to offspring
2. Fossil records
- Sedimentary rocks (eroded, moved and settled) -> early layers overlaid by recent
layers = time signature -> top layers recent & bottom layers older
- In layers imprint of animals of particular era -> different geological layers reveals
changing fossils -> e.g. size+shape skull
3. Structural similarity
- Across species comparative similarities -> e.g. paws, flippers, wings similar
skeletal structures but different fuctions -> developed from a common
ancestor -> environmental pressures cause progenitor organism to evolve into
whale/dog/human
4. Embryology
- Similar stages in utero (/uterus) across species
- E.g. human and fish embryos go through a phase having gills (= kieuwen,
evolutionary artefact of early life in water)
- Haeckel: ontogeny recapitulates phylogeny (ORP) theory -> during development
every organism goes through every stage of its evolutionary past -> similarities
reduced + embryo takes unique characteristics of their species (note, we weren't
fish)
5. Molecular biology
- Looks at elements of genes, forensic evidence of modern molecular
genetics
- We share common strands of genetic material with other organisms
The Organism and the Environment
▪ Idea genes influence behaviour -> nature vs. nurture/genes vs. experience
- Darwin: environment changes biology + behaviour over extended time period
- Complex interplay
- Johnson & Edwards: behavioural development product of interactions between
genetics, the environment and perception -> not purely determined by genes but
also by experiences, interpretations and perceptions of the environment (->
individual differences + environment isn't absolute)
o Evolution of Humans
Who/what were our ancestors? -> debates, religion
- Evolutionary theory: humans recent development, separated from animals, goes
back to life on earth
1) Birth earth 600 million years ago + water organisms
, 2) 450 million years ago organisms with nerves+bone structures -> spine (before
brain)
3) Amphibians: fish onto land -> fresh food+water -> survive+offspring ->
fins+gills evolving legs+lungs
▪ Living on land -> e.g. reptiles lay eggs+dry skin -> able living further from
water
4) Mammals evolved from reptiles 180 million years ago
▪ Breastfeeding -> developing internal process for offspring = pregnancy
▪ Different length pregnancy + multiple birth -> survival, subject to harsh
environment (in utero protection, but many challenges for foetus: unborn
offspring of mammal, particular more than 8 weeks after conception)
Humans exceptional mammals + most advanced form of primates (e.g. apes, very
similar to chimpanzees but not directly our ancestors)
- Members of Hominines: Australopithecus + Homo -> Homo Sapiens: primate
species to which modern humans belong
- 2 million years ago, from Australopithecus
- Early spieces bigger space for brain, but cavity modern human most big
- Africa -> 200.000 years ago fossil records and 50.000 years ago start migration =
'Out of Africa hypothesis' (recently Africans from Asia)
- Increase brain volume before arrival Homo genus + cuz using more tools ->
metopic sutures (joints in top skull) different from Australopithecus, fusion of
metopic sutures early in development compared to great apes+humans -> Falk:
selective pressures favoring delayed fusion might have developed from the
difficulty of giving birth to large-headed neonates, high early postnatal brain
growth rates, and reorganization and expansion of the frontal cortex
- Difference from chimpanzees -> idea changes in transcription+translation genetic
codes -> biggest difference = brain
1) Important changes in protein sequences in human genome: an organism’s
complete set of DNA
2) Duplication+deletion of genes
3) Further changes non-coding regions of the genome (involved in gene
expression)
4) E.g Humans lost some genes for olfactory receptors during primate-to-human
-> smell only sense doesn’t need to go through thalamus + important animal’s
perception of danger (adaption for survival, flight/fight response) -> humans
more reliant vision
- Brain:
1) Size
2) Complexity
➔ Size isn't everything, rather look at regional differences than brain
overall
3) Evolutionary development of vertebrate's spine (wervelkolom van
gewervelden)
- Brainstem: important sustaining life + similar across species
- Cerebrum (Grote hersenen): recent adaption, most developed part + more
developed than other species
- Cortex more convolutions (sulci, bochten) -> greater volume ->
neurons+communication the same but architecture+function uniquely human
,o Evolutionary psychology
- Comparative psychologists: look at behaviour of animals + try understand human
behaviour compared to other species -> we're descended from a common species
but separated from other animals during evolution
- Evolutionary psychologists: understand human behaviour from evolutionary
perspective -> certain pressures in environment give rise to certain characteristics
of human behaviour
*Why is a particular behaviour adaptive + still in behavioural repertoire
*Why is this maladaptive behaviour still present, what was its original reason for
being?
- Don't have hard evidence from the past -> e.g. fossil records don't give full
understanding, only clues for physical adaptations -> tendency more theoretical +
great controversy applied to human behaviour
o From Evolution to Genes
▪ Darwin same problem, didn't know how species differed/were similar, how particular
characteristics (anatomical/)behavioural were passed on to next generation -> no
access to mechanics of evolution -> evolved over time years later, starting with
Mendel, then modern genetics + unknown future
▪ Heritable characteristics/traits in behavioural genetics:
1. Qualitative - often influenced by 1 gene + simple pattern of inheritance
(like Mendelian inheritance: an inheritance pattern in which a genetic trait is
passed from parent to offspring and is either dominant or recessive). Phenotypes
are qualitatively different = either presence/absence of disease
2. Quantitative - typically unaffected by environmental factors -> e.g. Huntington's
disease
➔ Single gene disorders obey rules of genetics straighforwardly, but whole
process is not -> serveral factors may alter inheritance pattern of
characteristic/disorder
- Genetic heterogeneity: possibility clinically similar disorders are caused by
mutations in different genes, or mutations in same gene result in diverse
conditions -> some individuals with inherited disease-associated alleles don't
express the disease completely/partially = penetrance: an allele which doesn't
always lead to the disorder has low penetrance
- Mosaicism: a condition in which cells within the same person have a different
genetic make-up (not all body cells are genetically identical) -> caused by atypical
cellular divisions during early development -> e.g. Turner's syndrome: condition
that affect females when a sex chromosome is (partially) missing -> deletion of X
chromosome from normal XX genotype in some cells
Environmental factors (especially in utero) can cause similar disorders like those with genetic
origin = phenocopies (copies of the phenotype)
- E.g. Rubella virus + number of genetic defects can cause deafness
Qualitative traits started easy, but polygentic disorders immensely complex
- Multiple genes influence a quantitative trait: how much of the trait one has (not all
or none) -> doesn't follow simple patterns of inheritance -> more variable + less
predictable than qualitative traits
, - Phenotype isn't all-or-none phenomenon, expressed along a continuum -> e.g.
ADHD (quantitative trait) expresses various degrees of symptom severity along a
continuum (like attention with continuum of inattentive to overattentive; a
constant chain)
- Phenotypic expression subject to alteration + mitigation by environmental factors
- Many (not all) psychological phenomena + disorders are quantitative traits and
many disorders polygenetic -> by polygenetic characteristic/disorder, quantitative
trait loci (QTL): sequences of DNA linked to the genes that underline a quantitative
trait -> describes how multiple genes at different locations on the chromosome
contribute to the quantitative trait -> geneticists can investigate QTLs using
linkage(: tendency for alleles located on a chromosome to be inherited together)
analysis, looking for common occurrences in individuals who have a particular
characteristic/disorder
[Turner's syndrom:
- Chromosomal condition affecting female development before+after birth
(some genes express later in life)
- Mostly not inherited
- Occurs at random during gametes formation
- One X chromosome misses (XO)=monosomy: genetic condition in
which one chromosome lacks its homologous (see figure) -> in contrast
with trisomy: condition in which an extra copy of a chromosome is
present in the cell nuclei
- Mosaic Turner's syndrome: chromosomal change in only some of the cells
cuz errors occur during mitosis (celdeling)]
[ADHD (Attention Deficit Hyperactivity Disorder):
- Neurodevelopmental disorder, affects 5% of the paediatric population
(baby's+children)
- Main symptoms: extreme impulsivity, hyperactivity and lack of
attention
- Childhood disorder, but also in adulthood
- Most likely genetic (but inconclusive evidence cuz of potential
environmental factors)
- Suggesting symptoms arise cuz of imbalance of dopamine
... 86]
o Mendelian Genetics
Gregor Mendel:
- Differences in conspecifics (=members of the same species)
- Inheritance of behavioural+physiological+anatomical
characteristics
Experiment pea plants -> suprisingly extrapolateable to human inheritance
- 7 characteristics of pea -> examining dichotomous traits: characteristics/genes that
occur in one form or another, but not both (e.g. yellow or green pea) -> Y1+Y2 or
g1+g2 = Y1:Y2 or g1:g2 -> true breeding lines + produce same trait in subsequent
generations (Y/G), because they have the two factors of seed colour
, - True breed Y + true breed g =75% Y and 25% g in 2nd generation plants -> how?
- Only one trait appeared in 1st generstion cross = ! dominant trait (like either Y1 or
Y2) -> the recessive trait: trait that must be contributed by both parents in order
to appear in the offspring, e.g. phenylketonuria, (g1 and g2) wasn't expressed cuz
was overridden by the yellow seed trait (in Y1:g1, the Y1 factor is expressed + the
g1 factor is suppressed)
- In 2nd generation green-seeded plants were produced (g1:g2), despite not being
observed in 1st generation -> recessive trait was passed on to 2nd generation (as
with Y1:g1 plant) -> 1st generation plants carriers of recessive trait (g1), but cuz
combined with dominant trait (Y1) it wasn't observable = difference between
observed traits and genetic traits -> you see the phenotype + what you get
underneath in mechanisms of inheritance is the genotype (can be different)
- Phenotype: what is observed, observable characteristics of an individual
- Genotype: what is transmitted genetically, genetic constitution of individual
organism
- Is modern genetics -> each successive generation inherits two of dichotomous
traits/genes (1mother:1father, one from Y + one from g)
Eye Colour
- Adopts a Mendelian pattern of inheritance
- [When mother and father both have brown eyes, their child could have blue eyes,
without cheating being the case]
- Dichotomous trait: blue eye factor and brown eye factor -> mother and father can
both carry factor for blue eyes (b, revessive) + brown eyes (B, dominant)
1) When the gametes (ovum and sperm: male gamete and progenitor cell for new
organism) are formed they can only carry one factor (B or b) -> all offspring
with B factor will have brown eyes, regardless of whether they have a blue
allele
2) However if combination of sperm + ovum at fertilization results in bb then the
offspring will have blue eyes -> recessive b will only be expressed in the
company of another recessive b allele
People with one eye blue and one eye brown
- Different colour eyes could be due to either 1) heterochromia
iridium (= two different-coloured eyes within single individual)
or 2) heterochromia iridis (= variety of colour within single iris)
- Brown eyes rich in melanin + blue eyes lack it (melanin =
pigment giving colour to iris of the eye)
- Two of the genes that control eye colour:
- EYCL3, on chromosome 15 -> coding brown/blue eye (BEY)
- EYCL1, on chromosome 19 -> coding for green/blue eye (GEY)
➔ Not the problem, it's not inherited -> in heterochromia iridium the error
may be the 'reading' of the genetic code + heterochromia iridium could
be outcome of trauma -> example of environment/other conditions
beyond basic gene itself can influence a gene's expression or act as
phenocopies
