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Lecture 3
Finish Ch 2 - Missing Artificial Selection
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Last time in Anthr 1...
*Explained the pre-Darwinian view of biology
*Discussed the precursors of Darwin's Theory of Evolution
*Discussed Explanatory virtues
*Briefly discussed the resistance to Evolution
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Unpacking Scientific Explanations
Explanatory Virtues
Testability - Does the hypothesis produce testable predictions or retrodictions?
Background Knowledge - Is the hypothesis consistent with the facts independent
of those it is trying to explain?
Informativeness - Does the hypothesis specify a causal mechanism allowing us to
identify precise effects?
Parsimony - all things being equal, the explanation with fewer necessary
entities/hypotheses is more preferable to an explanation with more necessary
entities/hypotheses.
Good explanations will have these explanatory virtues
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Precursors Recap
John Ray (1627-1705)
-Identified reproductive isolation of species
-First to use "species" and "Genus"
Carolus Linnaeus (1707-1778)
-Binomial Nomenclature
-Taxonomic classification of biological
organisms
Comte de Buffon (1707-1788)
-Plants and animals interacted with the
environment
-Changes in the environment correlated with
changes in plants and animals
Jean-Baptiste Lamarck (1744-1829)
-Species change influenced by environmental
change
-First to really attempt and explain evolutionary
process
James Hutton (1726-1797)
-First to use Uniformitarianism
-the processes we see today to explain the geological history
of our planet
Georges Cuvier (1769-1832)
-Extinction
-Catastrophism
Charles Lyell (1797-1875)
-Father of modern geology
-The processes happening today were the same in the past:
Uniformitarianism
Alfred Wallace (1823-1913)
-Independently generated the concept of Natural Selection
-Father of Biogeography
Thomas Malthus (1766-1834)
-Populations grow exponentially while food
supplies/production grow arithmetically
-Populations outgrow food supply - survival of individuals
dependent on access to food supply or resources
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Origins of the Origins
Charles Darwin
(1809-1882)
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Natural Selection - Initial requirements
Individuals with favorable variations --> survive and reproduce at higher rates
Initial requirements for change by Natural Selection
1. All species produce offspring at a faster rate than the production of resources or food supplies.
2. Populations of individuals exhibit biological variation of characteristics.
3. More offspring are produced than survive due to competition for resources.
4. Individuals with favorable traits (speed, disease resistance, size) are more likely to survive than
individuals without those traits.
Fitness - A relative measure of reproductive success.
-Not who can live the longest but who can survive long enough to reproduce.
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Natural Selection
5. Favorable traits determined by environmental context - traits that give an individual an advantage in one
context might not in another.
6. Offspring inherit traits from a parental generation. Over time, favorable traits become more common in
a population.
Reproductive success - favorable traits are passed on with a higher frequency compared to less
advantageous traits which decrease in frequency over time.
7. Over extended intervals of time favorable variations accumulate in a population so much so that newer
generations are distinct from ancestral generations.
New species emerge
8. Geographical isolation - populations become geographically isolated and over time they respond to
selective pressures - different ecological contexts - to become distinct species.
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Natural Selection - Main Points
*Darwin was able to recognize that it was variation among the individuals of a population that contributed
to the change in a species over time.
Think about clones.
Natural selection operates on individuals but it is the population that evolves
Unit of Natural Selection - Individual
Unit of Evolution - Population
Individuals don't change genetically but overtime populations do.
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Natural Selection in Action
Peppered Moths
Industrial melanism in populations of peppered moths documented.
Shifts of pigment pattern frequencies in response to the change in the
environment caused by the industrial revolution.
Such responses are called adaptations.
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Natural Selection in Action - Finches
Evolution demonstrated in the finch populations
found on the Galapagos islands
-Measurements of beak thickness changed over
time in the population of medium ground finches.
Example of a favorable trait (thicker beaks) that
confers a selective advantage in a population
over time.
Finches with thicker-beaks had greater
reproductive success during droughts.
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Natural Selection in Action - Finches
Evolution demonstrated in the finch populations found on the Galapagos islands
-Measurements of beak thickness changed over time in the population of medium ground finches.
-Example of a favorable trait (thicker beaks) that confers a selective advantage in a population over
time.
Finches with thicker-beaks had greater reproductive success during droughts.
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Common Ancestry - Finches
Evolution demonstrated in the
finch populations found on the
Galapagos islands
-Measurements of beak thickness
changed over time in the population of
medium ground finches.
-Example of a favorable trait (thicker
beaks) that confers a selective
advantage in a population over time.
Finches with thicker-beaks had greater
reproductive success during droughts.
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Common Ancestry - Finches
Evolution demonstrated in the finch populations found on the Galapagos islands
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Natural Selection - Insights Gained from examples
1. Traits are inherited - otherwise natural selection cannot act
2. Populations of individuals exhibit biological variation of characteristics.
3. Fitness is relative - it changes relative to environmental change
4. Natural selection only acts on traits that affect reproduction
Fitness - A relative measure of reproductive success.
-Not who can live the longest but who can survive and reproduce.
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Issues with Darwin's Evolutionary Theory
???
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