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History of Natural Theology
 Classical Greek philosophers had ideas about the
natural evolution of life
 Plato (427-347 B.C.) believed there were two
worlds. A real world which was perfect and an
illusionary world that was imperfect.
 He did not believe in evolution.
 His student Aristotle (384 -322 B.C.) believed that
all forms could be arranged on a ladder or scale
called the “scala naturae” Each form of life had an
allotted rung on the ladder.
 Belief prevailed for 200 years.
Carolus Linnaeus(1707- 1778)
 Father of taxonomy.
 Taxonomy is the branch of biology concerned with
naming and classifying organisms.
 Came up with Kingdom, Phylum, Class, Order, Genus,
Species.
 However he believed there was no evolutionary
kinship between them.
Georges Cuvier(1769-1832)
 Paleontologist.
 Documented and recorded the succession of fossils in
sedimentary strata in the Paris Basin.
 Found deeper and older fossils to be dissimilar. New
species appear and older species disappear.
 Advocated catastrophism. Species killed off by
catastrophes and recreated.
James Hutton(1726-1797)
 Scottish geologist.
 Proposed gradualism .
 Profound changes are due to gradual changes over a long
period of time due to natural processes occurring within
the Earth’s crust.
Charles Lyell (1797-1875)
 Proposed uniformitarianism. The idea that geological
processes have not changed over time and are at work.
 Suggested the earth was a lot older than the previously
thought 6000 years.
 Processes persisting over long periods of time can
accumulate to substantial change.
Charles Lyell
Jean Baptist Lamark
 Was in charge of an invertebrate collection at the Natural
History Museum in Paris.
 Noticed that species changed over time.
 Proposed that phenotype can change in response to
environment changes and those new characteristics were
passed on to the offspring.
 First idea that adaptations occur in response to the
environment.
Jean Baptist Lamark
The Darwinian Revolution
 Charles Darwin(1809 -1882) was born in Shrewsbury,
England.
 Wanted to be naturalist but was sent to medical
school in Edinborough at 16.
 He dropped out and went to Christ College at
Cambridge University and became a clergyman.
Back then most naturalist were clergyman.
 Viewed the world as natural theologists.
 The view that each species was newly designed and
non-evolving.
Darwin 1875
Reverend Robert Henslow
 Botany professor at Cambridge.
 Darwin was his protégé
 At age 22 he was recommended to join Captain Robert
Fitzroy on the H.M.S. Beagle to sail around the world.
 The primary mission was to chart the South American
coastline.
 Darwin collected and observed the flora and fauna.
H.M.S. Beagle Voyage
Descent With Modification
A Darwinian View of Life
The Galapagos
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Species unique although they most closely
resembled South American species.
Darwin’s finches possessed different beaks to
accommodate different modes of eating.
Darwin read Principles of Geology by Lyell
and surmised that “old Earth” was inhabited by
evolving species.
Darwin’s Finches
The Origin of Species
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Lyell and a collegue presented Darwin’s work
Along with another British scientist by the
name of Alfred Wallace.
The paper was on the theory of “Natural
Selection” which Wallace and Darwin came up
with simultaneously.
Darwin published “The Origin of Species” a
year later.
Alfred Wallace
Darwin’s Observations
Species had distinct South American
characteristics.
 South American species that lived in the
temperate regions more closely resembled
the tropical species on the same continent
than species that resided in the temperate
regions on a different continent.
 South American fossils resembled South
American species.
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Observations That Lead Darwin to the
Theory of Natural Selection
OBSERVATIONS
 All species have the potential to reproduce
the maximum number of offspring.
 Populations remain stable (except for
seasonal fulgurations.
 Resources are limited
 CONCLUSION
 Organisms compete for food.
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Other Observations
 Organisms
vary
 Organisms with suitable traits
survive to reproduce.
 Gradual changes in a population
occur and the population
accumulates favorable
characteristics.
Additional Evidence for Natural Selection
 Homology similarities in characteristics due to a
common ancestor.
 Anatomical homologies
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similar structures, different function.
 Embryological homologies
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Similar structural development.
 Molecular homologies

Basic machinery of RNA and DNA are similar.
 Biogeographic homologies
Convergent evolution
Homologies
 Biogeographic homologies
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Endemic species.
Convergent evolution - species that look similar but have no
common ancestry.
Divergent evolution – species that have common ancestry but
evolve disparate characteristics.
 Fossil Record – the appearance of certain classes of
vertebrates in the fossil record.
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Fish before amphibians
Homologous Structures
Convergent Evolution
Natural Selection
 Differential success in reproduction.
 Variation in populations and how they respond to the
environment.
 The product of adaptation to their environment.
Descent With Modification
Cartoon of Darwin