PSYC 3420 Chapter Notes - Chapter 1: Mate Choice, Gene Page, Sexual Selection

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24 Apr 2012
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Chapter 1 Evolutionary Psychology
Foundations of evolutionary:
o Neanderthal man found 50,000 yrs ago, early homicide victim
o Fractures and dents more than women; left frontal skull; right handed attacker
Can’t tell us combat was normal or that more aggressive sex
o Brain is the most complex; 1,350 cubic cm; new goal of evo Psyc
o Focuses on 4 main Q’s:
o 1. Why it’s designed the way it is- what caused it to be...
o 2. How is human mind designed- mechanism and parts, organization
o 3. What are the functions of the component part and structure= whets its purpose
o 4. How does input from current environment interact with the design of the human
mind to produce observable behaviour?
Ancient Greeks A/P studied the mind; Freud too; skinner
Past few decades to see all disciplines coming together-Psyc, learning,
warfare, self-esteem, status, parenting all under one evolutionary psych
Landmarks in the history of evolutionary thinking:
o Evolution before Darwin:
Change over time, change in life forms before by scientists
Jean baptise Pierre Antoine de Monet chevalier de lamark-1744-1829 was one
of first to use word biologie thus studying life as a science
Lamarck believed: 1. Progress towards higher form 2. Inheritance of acquired
Must struggle to survive , enlarging nerve secretion, enlarging organs
Necks of giraffes probably from striving for higher leaves
These were passed down and acquired
Baron gorgers Cuvier 1769-1832- proposed theory catasrophism:
Species are extinguished periodically by catastrophes such as meteors;
replaced by other species
Some noted similarities of species to humans; birds to flipper; chimps to us...
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Change over time seen from fossil records, bones changed, organic structure
Embryonical development of different species: strikingly similar in species
that otherwise seems diff from another
Loop like pattern of arteries- same ancestors milling of yrs ago
All these evidences before 1859 suggested life was changing
Many also saw characteristics for certain species; quills of porcupine help
defense; turtle shell,
The mechanisms of change weren’t seen though
o Darwin’s theory of natural selection:
Why change takes place, and ways change proceeds; how new emergence,
vanishing species...etc...
Darwin took a voyage after Cambridge, on the beagle in 1813 for 5 yrs, to
Galapagos islands- found finches-m were all different yet same species
Common ancestor who diverged and local ecological conditions changed their
makeup- pivotal to Darwin’s conclusion that species aren’t immutable but
The existence of adaptations halted him from accepting others ‘explanations
Darwin used Malthus essay on population principle in 1798 to note that:
organisms exist in number greater than can survive and reproduce; struggle
for existence-favorable variations tend to be preserved; others die out
1. Theory of natural selection and 3 main ingredients
A. Variation b. Inheritance c. Selection
A.Variation:Organisms vary, this is essential for evolution to operate
and gives materials to work with evolution
B. Inheritance: passed down reliably parents to offspring; wing
deformities by accidents aren’t inherited by offspring-only those
variations that are inherited play role in evolutionary process
C. Selection: some heritable variants leave more offspring b.c. they
help with survival and reproduction
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Organisms can live many years and not pass its qualities to future; thus a
differential reproductive success- bottom line of evolution by natural selection
Differential-success or failure is defined by success relative to others; more
frequent if successful; b.c. survival is key for reproduction
o Darwin’s theory of sexual selection:
Survival selection-some things had nothing to do with selection at all;
Plumage of peacock seems to be open invite from predators;
Natural selection focused on adaptation to survival;
Sexual selection focused on adaptations for mating
A.Intrasexual competition: between one sex- outcomes to mates
o These traits will be passed on ; as female likes it
B.Intersexual selection: preferential mate choice; those who have
qualities desired, will mate-those who don’t wont.
o Aka- female choice- as they are choosy of mates
Sexual selection succeeded in explaining the anomalies
o Role of natural selection and sexual selection in evolutionary theory:
A/B aren’t only causes for evolutionary change
1. Genetic drift-
random changes in population, which come about through
A. Mutation- random hereditary dna changes
B. Founder effect- small portion of population makes a new colony
and are not genetically representative of the original population
o I.e. more red heds at beg. More red hed later on too
C. Bottle necks- population shrinks due to catastrophes; survivors have
only subset of genes of the original population
2. Intention-
Not intentional and cannot look into future; maybe giraffes long necks
will suck in 20 yrs, but now it’s good for those leaves
3. Gradual-
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