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Lecture 2

PSYB30H3 Lecture Notes - Lecture 2: Optimal Design, Exaptation, Pleistocene

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Marc A Fournier

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PSYB30H3: Personality Psychology
Lecture 2: Human Evolution
Outline of Today’s Lecture
P: Reflects our individual variation
It has been shaped by nature
Part I. Evolutionary Theory
The Evolutionary Process: Darwin
Variation: There is variation in design as a species.
Inheritance: Some of these differences are heritable (some are heritable acquisitions ex: a
scar) that we pass to our offspring. Design impacts our rates of reproduction.
Selection: Diff in design make differential impacts change environment and how we
Evolutionary Processes: Natural Selection
Identify natural selection: evolution of adaptive characteristics because of the survival
benefits bested on those who have them. Natural selection =survival
Example: longneck giraffes
Evolutionary Processes: Sexual Selection: evolution of adaptive characterizes b/c of reproductive
Goal is only to survive to reproduce (trying to maximize)
Intrasexual Competition (within the sexes) ex: stags’ antlers (reproductive advantage)
Members of one sex species end up competing to members of the other sex
Usually male species compete for female
Should increase in species
Intersexual Selection (between the sexes) ex: peacocks plumage (bright and beautiful)
Sex that does the choosing finds what is desirables should increase of evolve in frequency
or preference
Easier selective advantage due to plumage opposed to natural selective disadvantage
Products of the Evolutionary Process
Adaptations: design properties selected and coordinated towards solving recurrent problems in
the environment encountered by the ancestors of that species
Adaptations (“Evidence of special design”): ex- ears
Tend to be species typically
Tend to be universal of the species or gender of the species
Spandrels (“By Products”): a design property that does not directly contribute to
adaptions but is linked to adaptions or to adaptive properties.
Will have features of adaption at a genetic level ex: ear lobes not adaptive but genetically
correlated with ears
Random Effects (in genetic pool): (noise in the system) are adaptively neutral ex:
variation in ear lobe size
Species Typical: of the species or universal shared by every member of that species
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Suspiciously Functional: non arbiter ex: why do giraffes have long necks
Condensed Records of Ancestral Conditions: shape the species we are today
Adaptation ≠ Optimal Design
That which is adaptive is optimal (common assumption)
Is only adaptive to the present
Constraints on optimal design (3+)
Time Lags: always a time lag between when a problem appears in the environment and
when the evolutionary process generates a solution to that problem. In the time it takes
for the adaption to appear the world starts to change
Local Optima: local peaks. Only takes the step that is most beneficial to the species.
Insufficient Variation: some species must have genetic mutation in order to adapt the
new changes. That which doesn’t show up doesn’t get selected
Adaptations or Exaptations?
Exaptation (Gould, 1991): “a feature now useful to an organism that did not arise as an
adaptation for its present role but was subsequently co-opted for its current function”
Old part that is getting exploited for a new purpose
Ex: the feather of birds wings
Adapted function insulation
Exapted function flight
The Environment of Evolutionary Adaptedness (EEA)
The ancestral conditioned and selection pressures under which an adaptation evolved
The human EEA = the Pleistocene Epoch: 1.6 million years 10,000 years ago
The Life in the Pleistocene
Nasty brutish and short
Problem: Darwin Hostile forces of nature:
Ex: predators, parasites, food shortage, climatic changes and environment hazards
The Solution: Living Groups as Hunter Gathers
o Cop operative hunting of large game
o Collective defense
However groups imposed costs and defined several new problems to which our ancestors
had to adapt
Can’t Picture the Evolutionary Process? OK, then Think of Survivor.
Contestants have to:
Get along i.e. form cooperative reciprocal alliances
Get ahead i.e. negotiate the tribal hierarchy
Contestants adopt different social strategies; some of those strategies are more useful than
other, thus allowing some contestants to “survive” tribal council (the selective pressure)
and to “reproduce” themselves (and their social strategies) into the next round of play
Summary of Part I
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