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Summary Evolution and Genes
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Summary study book Psychology: The Science of Mind and Behaviour, 4e of Nigel Holt, Andy Bremner (Chapter 3) - ISBN: 9780077189624 (Chapter 3 notes)
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Chapter 3 – Genes, evolution and behaviourWe came from Neanderthals who experiences detrimental events that threatened survival,
otherwise we would not be here today; life back then was predatory, and our ancestors were
surrounded by vicious animals and scarce resources. Had they not experienced this, we would have
limited knowledge and primitive skills today.
We stud the effect of present- and past-day biology to understand the brain and cognition. Human
brains had tripled in size 1.6 million years ago. Australopithecus hominids had small brains which
increased in size over time. They are considered early ancestors of humans, but closely resemble
modern day chimps.
Evolution by natural selection
Evolution: gradual change over time from one form of organic life into another. Before Darwin’s
theory, everyone thought human life and organic life just came to be out of the blue one day rather
than undergoing gradual changes over time. People before Darwin did suggest the theory of
evolution, but his was most prominent due to the concept of natural selection, where a particular
population of certain organisms will live on, survive and reproduce to extend their familial line due
to having preferred traits that promote survival. Giraffes being tall, humans being good hunters and
eating meat and leafy greens provides more resources for surviving.
The grey wolf paved way for new dogs breeds today, even if the dog, so a shitzu, is nothing like the
grey wolf. Natural selection depends on competition over resources, high reproducibility between
animals and biological variation, which promotes adaptability. Some traits are species specific, like
having excellent hearing or having 4 legs to run on. If a wolf is thin but only a few are thick, then the
only way the thick fur coat wolves evolve more favourably is if the temperatures plummet and
adaptation does not help, thus when breeding, the traits become more centred around having thick
fur. So, thin fur coated wolves live in hot, arid climates whereas colder climates are home to thick
furred wolves.
Mutations: random events in gene reproductions when cells divide. Causes the change in physical
and behavioural traits over time. Discovered by Gregor Mendel, an Austrian monk.
Mendelian genetics
Mendel bred pigeons over time in England in order to assess physiological, behavioural,
temperamental and psychological changes over generations. Some were fatter, others cooed
differently. It was easy to measure pigeon differences because bird have complex and specific
behavioural patterns, like building, hunting and caring. They even have specific migration paths. So,
if they were bred, monitoring changes to these regimes was easy. Mendel conducted the pea pod
experiment, studying colour, shape, traits and size. He discovered that genes come in pairs from
both parents, with some being dominant and others recessive, affecting the rate at which traits are
most visible.
Dominant genes control the characteristic displayed, whereas in recessive pairs, both genes must be
recessive to produce the characteristic. Alleles help produce different combinations of genes which
, then produce a particular set of genomes and phenomes. Having a dominant and recessive pairing
produces characteristics that carry the recessive gene but produce the characteristics of the
dominant gene.
Gametes (egg and sperm) carry only one allele, with fertilisation combining DNA and parental genes.
Homozygous: carrying two matching alleles, a dominant or a recessive pair only. Blue eyes and red
hair are homozygous, recessive genetic traits.
Heterozygous: Carrying both, dominant and recessive alleles, as a pair.
Genotype: individual genetic code.
Phenotype: Visible, observable characteristics, like hair colour.
Genotypes are present at birth; however, the phenotype can be altered by decisions and the
environment (tanning, dying hair etc.). Genotype means having inherited the blue eye, recessive
trait, but the phenotype is having brown eyes. You can pass this onto your child provided the
homozygous allele pairing is present.
Phenylketonuria: a condition causing learning disabilities and developmental delays, as a result of
inability to metabolise the amino acid phenylalanine. It is treatable by good diet starting from
infancy and it cannot be passed on without a recessive pairing. Being a carrier only increases the
chances, there is no determination of passing it onto your offspring.
Huntington’s disease: causes a change in personality, problems with memory, motor functioning
and mental capacity. It is genetic and low GABA contributes to the intensity. Unaffected individuals
have two recessive alleles, since Huntington’s is inherited by having a dominant gene in the pairing.
Symptoms are onset after the age of 40.
Eugenics
It was suggested by Francis Galton, who claimed we should hinder the inheritance of unwanted,
undesirable traits, by preventing people with these characteristics from breeding. Instead, people
with high intelligence, favourable heights and weights as well as desirable personalities should be
breeding.
There is no moral compass behind evolution. Humans are considered the mightiest purely because
we can adapt to our surroundings and learn from experiences in order to survive, which extends our
lineage. However, if we were wiped out and smaller organisms would live, then they are the
successful, surviving species, not us.
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