Transcript Darwin’s Daring Kitcher: “Believing Where We Cannot Prove”

Darwin’s Daring
Kitcher: “Believing
Where We Cannot
Prove”
Pages 332 -335
Darwinian History
1.
2.
Describe an ancestral population of
organisms.
Trace modifications of the population
through the subsequent generations,
showing how characteristics were selected,
inherited, and become prevalent.
Many Purposes
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Can describe why a trait exists
Can describe relationships between organisms
Can account for similarities and differences among
species
Can explain organisms’ locations
Can try to explain extinctions
Can be used in many broad classes of biological
phenomena
Evolutionary Theory in
Action: Madagascar
Island inhabited by a peculiar group of mammals, most of
which are endemic
 tenrecs: small, insectivorous mammals
: features mark them as primitive
: have specialized characteristics similar to
other animals that do not inhabit this island (convergent
evolution)
Why are they found here
and nowhere else?
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Evolutionary Story
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In the late Mesozoic or early Cenozoic
period, primitive mammals rafted across the
Mozambique channel to Madagascar.
Channel widened, preventing more
advanced mammals from crossing.
The tenrecs were protected.
Without competition, they have maintained
the simple body plan and exploited
unoccupied niches.
Claims Subject to Independent Check:
Madagascar
1.
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Madagascar drifted away from Africa’s east
coast.
Can check using geological criteria for the
movement of land masses (criteria
independent of biology)
2. Tenrecs could have rafted across the
Mozambique channel, but that the present
channel is a barrier to more advanced
mammals.
 Test by looking to see if the animals in
question can disperse across channels of
appropriate size.
3. Specialized methods of defense are
advantageous against predators on
Madagascar.
 Study animal interactions to see if certain
defenses are effective against local
predators.
4. Tenrecs are related.
 Studies of minute features of tenrec anatomy
should reveal common features; should have
similar protein structure.
Darwin’s theory can be compared to
Newton’s Physics.
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Unified theory whose problem-solving
strategies are used in many different areas.
Problem solutions can be independently
checked.
Open new questions.
History of surmounting apparent obstacles.