Download History of Evolutionary Thought

History of Evolutionary
Thought
Why is there a diversity of life?
Plato
(427-347 B.C.)
• Real World  Ideal
• Perceived World 
Imperfect via Senses
• **No need for
evolution because
organisms are
already perfect.
Aristotle
• Scala Naturae  All
life organized on a
scale, or ladder, of
increasing complexity.
• Organisms are fixed
at each “rung”.
• No evolution of
species.
(384-322 B.C.)
Old Testament
• Judeo-Christian
culture
• Species individually
designed and
permanent
• No evolution of
organisms
1700 A.D. Europe
• Natural Theology
• Adaptations or organisms  evidence
organisms were created with purpose.
• Taxonomy  Reveal steps of scale of life
created by God.
– Linnaeus  System we use today
• K, P, C, O, F, G, S
Georges Cuvier (1769-1832)
• Paleontology – study
of fossils in France.
• Documented changes
in organisms present
in each rock layer.
• **Catastrophism –
boundary layers
caused by local
catastrophe and
repopulated by
organisms migrating
in.
James Hutton (1726-1797)
• **Gradualism –
geological features
are cummulative
products of slow, but
continuous processes
• Canyons formed by
rivers cutting through
rocks as observed
daily.
Charles Lyell (1797-1875)
• **Uniformitarianism –
Geological processes
have not changed
throughout Earth’s
history.
Hutton + Lyell to Biology
• 1) Geological change results from slow,
continuous actions rather than sudden
events and therefore, the Earth must be
very old (older than 6000 years as
proposed by theologians)
• 2) Very slow and subtle processes
persisting over a long period of time can
cause substantial change.
End of 1700’s
• Many naturalists suggested that life had
evolved along with the evolution of Earth.
Jean Baptiste de Lamark
(1744-1829)
• Invertebrate
Collection in Paris
• Saw many lines of
descent of older to
younger fossils
leading to modern
• Species move up the
ladders to greater
complexity
Lamark (cont.)
• Evolution was driven by an innate tendency
toward perfection.
• Evolution responded to organisms needs.
• Mechanism of Evolution:
– 1) Use and disuse – those parts used
extensively to cope with environment
enlarged and those not used reduced in size.
– 2) Passing on of Acquired Traits
• Traits one develops in one’s lifetime – read,
music
Lamark (cont.)
• Nice theory…No evidence that Acquired
Traits can be passed on.
– Biceps of Blacksmith, removed tails of mice
• Deserves a lot of credit:
– Evolution best explaination for both fossil
record and current diversity of life
– Recognition of great age of Earth
– Adaptation to Environment as product of
Evolution
Charles Darwin (1809-1882)
• 1) The occurrence of
Evolution (Descent
with Change) – Unity
of life related by
descent from some
common prototype.
• 2) Mechanism is
Natural Selection
Natural Selection
• 1) Species produce more offspring than
can survive
• 2) Struggle for survival- limited
environmental resources
• 3) Variation within a species – no two
humans (except identical twins) alike.
• 4) Those best suited for the environment
are selected by nature to produce more
offspring.
Darwin (cont.)