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Chapter 3

ch.3 textbook notes detailed


Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens
Chapter
3

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Chapter 3: The Development of Evolutionary Theory
Biological evolutionchanges that take place in genetic and physical
chracteristics of a population or group of organisms over time
Adaptive significanceeffectiveness of behaviour in aiding organisms to
adjust to changing environmental conditions
psychologists research how past environmental conditions favoured certain
behaviour and how immediate envornment influences choices – interested in
ultimate causes of behaviour and proximate causes
ultimate causes – evolutionary conditions that have slowly shaped behaviour
of species over generations
proximate causes - immediate environmental events and conditions that
affect behaviour
Clark and Galef – different behaviour of male gerbils next to other male or
female in utero traced to presence or absense of testosterone during
gestational periods – evolutionary reason?
Clark, Desousa, Vonk, and Galef – examined subsequent behaviours of
male gerbils who were gestated next to females: when they did mate
successfully gerbils were good fathers – spent time in contact with pups, and
mates became sexually active more quickly (mating stratefy – better
performers or parents)
by understanding adaptive behaviour developed through long-term process of
evolution, psychologists are able to gain better understanding of our abilities to
adjust to changes in immediate environment – members of human species
(ultimate cause) and have learned to act in certain ways (proximate cause)
evolutionary psychology – studies ways which organism's evolutionary
history contributes to development of behavioural patternsa nd cognitive
strategies related to reproduction and survivial during lifespan
culture – sum of socially transmitted knowledhe, customs, and behaviour
patterns common to particular group of people
British naturalist Alfred Russel Wallace also devised theory natural selection
same time as Darwin
Voyage of the Beagle
Christ's College – degree in Theolody
met captain Fitz Roy in 1831 – unpaid naturalist companion on Beagle, ten-gun
brig converted to ocean research vessel that ended in 1836
mission was to explore and survey coast of SA and to make hydographic
measurements worldwide – almost rejected bc of shape of nose (couldnt
possess needed energy and determination)
Darwin observed flora and fauna of South America, South Africa, and islands of
Pacific, South Atlantic, and Indian oceans, including Galapagos – collected
creatures and objects and sent them back to England to be studied by
naturalists of Europe
naturalism – ascribed doctrine of essentialism, dating back to Plato that all
living things belong to fixed class or kind, defined by an essence that
characterizes it alone
didnt come up with theory of evolution until after trip

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The Origin of Species
compared similarities and differences in creatures he had found adn carefully
reviewed work of earlier naturalists, including grandfather, who had specualted
about concept of evolution but were unable to propose believable process by
which it occured – became interested in artificial selection and bred pigeons for
a while
artificial selection – procedure in which animals are deliberately mated to
produce offspring that possess particularly desirable characteristics
natural selection – concequence of fact that, because there are physical and
behavioural differences among organisms, they reproduce differently; within a
given population, some animals – the survivors - will produce more offspring
than other animals
came to this realization in September 1838 but did not publish until 20 years
later because wanted supportive evidence
Wallace sent his theory to Darwin, which he developed during a bout of fever
in Spice Islands after reading Mathalus populationpresented theory together
to Linnean Society and Darwin published the Origin of Species a year later
Natural Selection and Evolution
Mayr – suggested that Darwin's immense contributions to modern thinking
about evolution can be traced to four insights:
species are not fixed but rather change over time; evolution is branching
process, implying that all species descend from single common ancestor;
that evolution is continuous, with gradual changes; and that evolution is
based on natural selection
Natural Selection
based on two premises:
individuals within population show variability in heritable behavioural and
physical characteristics
capacity of environment to sustain a population of any species is limited,
producing competition
behavioural adaptations were especially important to survival and therefore an
important part of evolution
reproductive success – number of viable offspring an individual produces
relative to number of offspring produced by members of same species;
evolutionary “bottom line”
Variation
variation – differences found across individuals of any given species in terms
of their genetic, biological (size, strength, physiology) and psychological
(intelligence, sociability, behaviour) chracteristics
caused by individual's gentic makeup (genotype) and as a result physical
chracteristics and behaviour (phenotype – outward expression of organism's
genotype; physical appearance and behaviour) vary
phenotype is produced by interaction between genotype and enviornment -
genotype determines how much environment can influence organism's
development and behaviour

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Peter and Rosemary Grant – studied finches and noticed that amount of
rainfall and size of food supply directly affected mortality of finches having
certain types of beaks (drought - small seeds scarce so small beaked birds die)
made two important points:
although evolution occurs over long run, natural selection can produce
important changes in short run – only a few years
phenotypic variation can produce important selective advantages that
affect survival
Competition
competition – striving or vying with others who share same ecological niche
for food, mate and territory
Rele, Mcdam, Boutin, and Berteaux – found that average time at which
female squirrels gave birth advanced more than two weels in just ten years
coinciding with increased amount of pinecones stored in trees
found that each new generation produced a birthdate that was about one
day earlier than that of previous generation
can use correlation methods
Natural Selection in Human Evolution
early hominid Ardipothecus ramidus lived about 4.4 million years ago in Africa
later creatures Australopithecus anamensis and Australopithecus afarensis
were clearly similar and bipedal
viewpoint supported from statistical evidence is that over oeriod from 3-2
million years ago homonid line split in 2 – African environment turned drier,
altering sources of food
one line evolved into genus with powerful jaws that could crush and chew
plants and nuts – Paranthropus and other line continued to form
Australopithicus that formed two distinct species 2.5-1.8 million years ago –
Homo rudolfensis and Homo habilis (handy man – originator of stone tools)
Hominids has encepholizationincreased brain size, requires more calories,
tools an advantage
disputed way it altered hominid life – either associated with specific home base
used by groups to share food and raise children or carried with them to help
scavenge meals
hominids left african home 1.8 million years ago used stone chipped tool –
homo erectus found as far as in Java and China
600,000 years ago Homo heidelbergensis prepared very planned tools – single
directed blow would detach finished tool
sapiens and neanderthalensis evolved from that species
originated in Africa 150000-200000 years ago
success stems from bipedalism and ecephelization
Dunbar – suggests that homo sapiens evolved in environment that favoured
large groups
large groups can remain together only if they can remember small nuances
that underlie social interactions
correlation between primates with encephalization and large groups
humans can naturally function in group of 148
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