Transcript The Received View of Evolution - hu

20.04.2005
The Received View of Evolution
Sex and Death: An
Introduction to
Philosophy of Biology
Contents
2.1 The Diversity of Life
2.2 Evolution and Natural Selection
2.3 The Received View and its Challenges
2.1 The Diversity of Life
“design space” (Dennett, 1995)
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All possible and actual “designs”
Regarding these we are highly atypical
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Eukaryotic + simply life cycle + huge
Diversity and Disparity (Gould)
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Diversity: number of species in existence
Disparity: amount of organisms that have
fundamentally different designs
2.1 The Diversity of Life
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Process Structuralists
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Why are some areas in design space
occupied and some not?
Design space is highly constrained
Historical relativity
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There are so many designs, that there was no
time to realize them all.
?
2.1 The Diversity of Life
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Why do organisms come packed into
species?
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Life without species is possible
No sharp distinction between spiecies and
varieties
2.2 Evolution and Natural Selection
Basic elements of evolutionary theory (Mayr)
1. The living world is not constant
2. Evolution. change has a branching pattern
3. New species form when a population splits
4. Evolution. change is gradual
5. Adaptive change through natural selection
2.2 Evolution and Natural Selection
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Natural selection is the inevitable result of
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Phenotypical variation
Differential fitness
Heritability
Are the forces that induce genetic variation
deterministic?
?
2.2 Evolution and Natural Selection
Cumulative selection
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Innovation is the result of a sequence of selective
episodes
Conditions:
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Direction of selection is constant
Low mutation rate
Each intermediate stage must be fitter than its
predecessor (adaptive landscapes)
2.2 Evolution and Natural Selection
Speciation
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Cumulative selection in different environments
results in reproductive isolation
Hybrid matings will be penalized
2.3 The Received View and its Challenges
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3 important debates
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Units of selection
Selection and evolution
Evolution within Biology
2.3 The Received View and its Challenges
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What is being selected
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“gene’s eye” concept (Williams, Dawkins)
Hierarchical view
2.3 The Received View and its Challenges
The “gene’s eye”
 Only genes are passed on directly from one
generation to the next
 Genes are replicators and use organisms as
“vehicles”
 Natural selection acts through vehicles and
targets the replicators
 Problem: gene – trait relationship
2.3 The Received View and its Challenges
Hierarchical view
 organisms are not the only entities that form
populations (hives, colonies, species)
 Selection can operate simultaneously at
different levels
2.3 The Received View and its Challenges
Selection and Evolution
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Four major issues
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Does the received view overstate the importance
of adaptation?
Relationship of selection and other factors
Methodological issues
The proper scope of evolutionary explanations
2.3 The Received View and its Challenges
The Importance of Adaptation
 Fitness advantages only make survival more
likely !
2.3 The Received View and its Challenges
Relationship between selection and other
factors
 Selection is historical, it is constrained by
inheritances of the population
 Some patterns seem to be independent of
selection:
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Evolution after the Cambrian explosion
2.3 The Received View and its Challenges
Methodological issues
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How can we test our ideas?
How much evidence is needed to support a
hypothesis?
2.3 The Received View and its Challenges
Scope of evolutionary explanations
 Sociobiology (Wilson)
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Explaining social / psychological processes with
evolutionary mechanisms is possible
vs.
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This attempt is mistaken in principle. Since there is
culture these rule do not apply to us anymore
2.3 The Received View and its Challenges
Evolution within Biology
 Evolution and Ecology
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Ecology describes the environment which
generates selective pressure
Evolution and molecular Biology
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Genetics did not make Evolutionary Theory futile
Different levels of explanation