Evolution: Did recognition of evolution as a
natural process begin with Origin of the
Species?
Nope
Evolution was discussed and debated for
over 100 years before Darwin published his
work
These discussions helped lay the
foundation for Darwin’s Theory of
Evolution by Natural Selection
Changes in Scientific Thought Through
Observation and Investigation
• Judeo-Christian culture - species were
individually designed and permanent
• Natural Theology – 1700s, discover the
Creator’s plan by studying nature
• Natural Theology was based on the body
of knowledge available at that time
Carolus Linnaeus and Taxonomy
• Reveal steps of life
fashioned by the
Creator
• Science of taxonomy
came of this
• Linnaeus’
classification system
was important to
Darwin’s work
• System is still in use
today
Fossils and Cuvier
• Relics or impressions
of remains of
organisms
• Intense study of
fossils began in 1700s
(paleontology)
• Found in
sedimentary rock,
revealed by erosion
Paleontology refined as a
science by
Georges Cuvier (1769-1832)
Fossils and Cuvier
• Cuvier recognized fossils deposited in
layers (strata)
• Observed that species disappeared and
new ones appeared in different strata
• Disagreed with evolutionists of his time
Catastrophism
• Cuvier proposed that each boundary
between strata corresponded to some
catastrophic event
• Event destroyed many of the taxa present
at time
• Event was localized
• New species came from unaffected areas
Catastrophism
• Cuvier’s worked in a limited geographic
area
• Later discoveries of similar strata in
other areas revuted Cuvier’s theory
Gradualism
• James Hutton (1726-1797)
proposed a theory that
contrasted with Cuvier’s
• Gradualism
• Geological formations are
the product of slow but
continuous processes
• Influential in the
understanding of evolution
Uniformitarianism
• Charles Lyell (1797-1875)
• Incorporated gradualism
into his theory of
uniformitarianism
• Rate at which geological
processes occur has stayed
the same throughout
Earth’s history
• These rates meant Earth
had to be older than 6,000
years
Lamark: An Evolutionary Theory
• Jean Baptiste Lamark (17441829)
• Proposed the first
comprehensive model of how
life evolves
• Published in 1809 (year
Darwin was born)
• Lamark studied invertebrates
• Lineages from fossils to living
species
Lamark: An Evolutionary Theory
• Perceived evolution as an organism’s
attempt to achieve perfection
• Innate tendency toward greater complexity
• Equated increased complexity with
perfection
• As organisms attained perfection, they were
better adapted for the environment
Basis of Lamark’s Model
• Lamark based model on two popular ideas
of his time
– Use and Disuse
– Inheritance
Use and Disuse
• Continued reliance on one or more
characteristics would make that/those
characteristics better adapted
• Disuse would cause a feature to be lost
• Acquired adaptations from use would be
passed to next generation
• Example - Blacksmith
Inheritance
• Lamark was describing the inheritance of
acquired traits
• Acquired traits are features developed by
an individual and are not genetic; therefore,
cannot be inherited
Ridicule of Lamark
• Evolution was not widely accepted in the
scientific community
• Ridiculed by Cuvier
• Ridicule today based on Cuvier’s comments
• Lacked supporting data
Lamark’s Contribution
• Use and disuse
• Adaptation to the environment
• Inheritance
The Darwinian Revolution
• Darwin studied for the clergy (most
scientists and naturalists did)
• Most ships travelling to distant lands
carried a naturalist
• Darwin joined HMS Beagle as naturalist
on a trip around the world
• Assignment was to collect, plant, animal
and fossil specimens
Darwin Focused on Adaptation
After Returning
• Fossils and living plants and animals of
South America and Australia were
unique to those regions
• Galapagos Islands
– geologically young islands
– apparent differences in flora and fauna of
each of the islands
– differences among similar plants and
animals on same island
Darwin Focused on Adaptation
After Returning
Organisms appeared to differ in response
to the conditions of their environment
Main Points of The Origin of Species
• Biological diversity is the product of
evolution
– Descent with modification
– “Tree of Life” and Linnaeus’ classification
system
• Natural selection as a mechanism
through which evolution proceeds
Process of Developing His Theory
• Observation #1 - Species have the ability
to produce an excess number of young
• Observation #2 - Populations tend to
remain stable in size
• Observation #3 - Resources are limited in
availability
Process of Developing His Theory
• Observation #1 - Species have the ability
to produce an excess number of young
• Observation #2 - Populations tend to
remain stable in size
• Observation #3 - Resources are limited in
availability
– Inference #1 - Production of more
individuals than can be supported
leads to a struggle for existence, with
only some of offspring surviving
Process of Developing His Theory
• Observation #4 - Individuals in a
population vary extensively in their
characteristics
• Observation #5 - Much of this variation is
heritable
Process of Developing His Theory
• Observation #4 - Individuals in a
population vary extensively in their
characteristics
• Observation #5 - Much of this variation is
heritable
– Inference #2 - Survival in struggle for
existence is not random. Individuals with
characteristics that improve chance for
survival are the most fit.
– Inference #3 - Differences in probability
to survive will lead to change in a
population
What does natural selection mean to us?
• Changes in the makeup of a population in
response to fluctuating environmental
conditions
• Loss and gain of species
Reception for Darwin’s Theory
During His Time
• Most biologists were convinced about
evolution
• Natural selection not widely accepted
• Why?
Basic Tenet of Natural Selection
The most fit organisms (survivors)
will reproduce and pass their genes
on to the next generation.
Problem – Process of inheritance not understood
Gregor Mendel
• Presented his work in 1865
• Was largely ignored, in fact ridiculed
• Was rediscovered in early 20th century
“Marriage” of Mendel and Darwin
• Early interpretation of Mendel’s work
did not provide support for natural
selection
• “Either/or” traits
• Natural selection requires variation in
traits
• Later recognized variation does exist
(population genetics)
Modern Synthesis
• Developed in 1940s
• Integrated natural selection and genetics
• Integration of several disciplines
– paleontology (Simpson)
– taxonomy (Mayr)
– genetics (Dobzhansky)
Modern Synthesis
• Evolution occurs at level of population,
not the individual
• A population has a gene pool, with some
frequency of occurrence for the alleles
that express respective traits
• Evolution produces changes in the allele
frequencies of a population
Main Points of Exercise
• Darwin - mechanism for evolution, not
evolution itself
• Evolution – idea present before Darwin
• Body of Knowledge
• Scientific Scrutiny/Skepticism