Download History of Evolutionary Thought

9/27/2012
History of Evolutionary Thought
Epistemology and Evolution
• Argument from Authority
– Reality can be explained by scripture or by
persons
• Methodological Naturalism
– Nature to explain nature
– Supernatural explanations are not allowed
Rise and Fall: in a nutshell
• Greeks used methodological naturalism
• After, Aristotle and scripture used for
knowledge
• Methodological naturalism rejected – not
entirely
• 18th century: Age of Enlightenment
Aristotle (384-322 B.C.E.)
Plato’s student
Studied ecology, biology, and geology
Continued Plato’s idea of eidos
Concept of eidos for species persisted until
Darwin
– Search for laws
Age of the Earth
• Greeks: eternal
• Bible scholars: ~ 5000 years
• George Buffon (1707 – 1788), French naturalist
– 75K to 2-3M years
– Used observations
• James Hutton (1726-1797), Scottish geologist
Charles Lyell (1797-1875)
• Principles of Geology (1830)
• Based on uniformitarianism
• Was the geology textbook of
Darwin’s day
• Friend of Darwin
– Founder of modern geology
– Earth is incredibly old
– Uniformitarianism
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Natural History and Classification
• Aristotle proposed a simple
classification with genus and
species
• Scala naturae: Great Chain of Being
• Karl von Linne (Carl Linnaeus,
1707-1778)
– Binomial nomenclature
– Systema naturae
– Was all about sex!
Organisms and their environment
• William Paley (1743-1805) Natural Theology
– God as Watchmaker
• Extinctions are impossible
– Lewis and Clark
• Georges Cuvier (1769-1832), French
– Father of paleontology
– Extinctions are real
Change through time
• Greeks proposed it
• Bible scholars forbid it
– Organisms created perfectly
– Immutability of species
• Erasmus Darwin (1731 – 1802)
– Charles Darwin’s grandfather
– Zoonomia (poem)
– Organisms evolve in scala naturae
– Publically ridiculed
Change through time
Change through time
• Robert Chambers
– Vestiges of the Natural History of Creation (1845)
– Organisms evolve
– Process is slow
– Emphasis on populations
• Jean-Bapiste Lamarck (1744-1829)
– Zoological Philosophy (1809)
– Inheritance of acquired characteristics
Along came Darwin 1809—1882
• Grandfather and father were doctors
• Went to Edinburgh for two semesters to study
medicine – dropped out
• Went to Christ’s College to be a clergyman
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Studied natural theology: geology and natural history
Energetic field student
Urged to go aboard the HMS Beagle
The captain (Robert FitzRoy) needed a companion of
similar social stature
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Voyage of the HMS Beagle
Voyage of the Beagle
• Surveying trip
– Map coastlines
– Test new equipment
• Naturalist on board was the doctor
• Was supposed to be three year journey – went
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• Left 1831, Darwin age 22
• Went to Azores, S. America, Galapagos,
Australia, Tahiti
Voyage of the HMS Beagle
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Darwin collected fossils and living organisms
Ship’s official naturalist left
Darwin shipped materials back
Became famous as a naturalist
Wrote several books soon after
Voyage of the HMS Beagle
• Observations
– Each Galapagos island had
its own turtle, mockingbird
– Fossil species similar but
not the same as extant
species
– Similar species over land
masses
– Struggle for existence
• Thomas Malthus
Darwin, from boat to book
• After the Beagle trip, married and settled in
the country
• Studied barnacles, worms, seeds
• Researched like mad
• Did not work for a living
– Married cousin, invested, inheritance
• Thought about natural selection and evolution
• Thousands of letters of correspondance
Alfred Russel Wallace (1823-1913)
• Studied butterflies in
southeast Asia
• Knew many of the same
facts as Darwin
• Sent Darwin an outline of
natural selection in 1855
• In 1858, co-authored a
paper with Darwin on
natural selection
• Not a big hit
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Origin of Origin
Natural selection sensu Darwin
• Happens when
• Inspired by Wallace, finally published his draft On
the Origin of Species by Means of Natural
Selection, or the Preservation of Favoured Races
in the Struggle for Life in 1859
• Stressed the importance of variation within a
species
• Natural selection
• Common ancestry: hierarchical branching
– Taxonomy reflects ancestry
Process related to artificial selection
– More organisms are born than can survive and
reproduce
• Competition to represent the next generation
– Those organisms more likely to survive because of
some trait will leave more offspring
– If that trait is heritable then the offspring will have
that trait
– If conditions continue then that trait will spread in
the population
Major Darwinian Ideas
• Natural selection
• Common ancestry
Interspecific variation
There are fitness consequences to this variation
• Organisms vary within a species
Male tail streamers length as a predictor of reproductive success: (a) First brood breeding
success, (b) Annual breeding success, (c) Successful genetic offspring in first brood, and (d)
Annual genetic breeding success.
Vortman Y et al. Behavioral Ecology 2011;beheco.arr139
© The Author 2011. Published by Oxford University Press on behalf of the International Society
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The variation is heritable
Natural selection occurs
Dave Reznick
Caribbean Anoles
Common Ancestry
• Phylogenetic trees
Pre-Darwinian Linnean classification
Species
A
Species
D
Species
E
Genus C
Genus G
Species
B
Species
F
Family H
Post-Darwinian Classification
Species
A
Species
B
Species
D
Common
Ancestor C
Species
E
Species
F
Common
Ancestor G
Common
Ancestor H
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Phylogenetics and Taxonomy
• Pre-Darwinian Taxonomy
–Classification arbitrary
Reception of Origin
• Most scientist accepted evolution
• Natural selection not as widely accepted
• Post-Darwinian Taxonomy
–Classification represents lineages
–Taxon = monophyletic group
• Taxonomy should reflect phylogeny
Issues with Darwin
• Eusocial insects
• Mechanism of heredity unknown
• Time
To recap
• Darwin’s contributions
– Evidence that evolution happened
– Mechanism of evolution: natural selection
– Pattern of evolution: heirarchical
Rise of the Geneticists
• Weisman's germplasm hypotheses
– Contra Lamarck
• Hugo DeVries
– worked with mutations
– genes
• Early Geneticists
– Variation was discrete
– Mutations produced large changes
• Naturalists
– Most variation was continuous
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Population Genetics
• Resolved the dispute between naturalists and
geneticists
• Modern Synthesis of 1940’s
– Ronald Fisher
– Theodosius Dobzhansky
– Sewall Wright
– JBS Haldane
– Ernst Mayr
– George Simpson
Population Genetics
• Evolution is
– Descent with modification
– Change in gene frequency
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