2. The True Story of the
Theory of Evolution
Or Fitzroy, Fickle Fuegians, and Funny,
Feathered Finches
3. 1973: “Nothing in biology makes sense, except in the
light of evolution.”
-Theodosius Dobzhansky (1900-1975)
4. Evolution, Pre-Darwin
Beginnings in Ancient Greece
Species are changeable… Variation occurs!
Selective breeding utilized already
“Artificial Selection”
Widely accepted in early-1800s: Lamarck’s
Theory of Acquired Characteristics
5. Jean-Baptiste de Lamarck
1744-1829
1. Individuals lose
characteristics they do
not require (or use) and
develop characteristics
that are useful
2. Individuals inherit the
traits of their ancestors.
6. Thomas Malthus
Malthus: An Essay on The
Principles of Populations (1798)
Populations grow exponentially
while food supply grows linearly.
Eventually population will
outgrow food supply; life is a
constant struggle
What keeps a population in
check? War, pestilence, famine,
competition, etc.
7. Charles Lyell
Principles of Geology
(1830)
“The present is the key
to the past.”
Geologic change is the
steady accumulation of
tiny changes over a
lengthy period of time.
8.
9. Charles Robert Darwin
Born in 1809, same day
as Lincoln
Wealthy, upper-class
Father, Robert, was a
physician and anti-
evolutionist
Grandfather, Erasmus,
was pro-evolutionist and
gifted debater
10. Darwin’s Career
Robert: “You will be
a disgrace to
yourself and all of
your family”
Eventually earned a
degree in divinity
from Cambridge
11. The HMS Beagle
First voyage: May 22,
1826
Captain Pringle Stokes
Mission: survey coast
of southern South
America
12.
13. First Voyage of the Beagle
Stokes – suicide
Robert Fitzroy
becomes captain:
seeking a literal, biblical
interpretation of
creation
Boat stolen
Fuegians captured as
hostages, then returned
to England
14. The Beagle’s Second Voyage
Darwin – captain’s
companion
Fitzroy and Darwin –
devoted observers of
the natural world
IMPORTANT – Darwin
did not SET OUT to
discover natural
selection
15. Darwin’s Finches
Galapagos islands
(Pacific Ocean)
Finches uniquely related
to the individual islands
Ornithologist John Gould
helped Darwin make
his…
HYPOTHESIS:
Modification of original
group of finches that
colonized islands
17. Darwin’s Later Life
Returned to England in
1836 and never left again
Suffered frequent
illnesses, probably
tropical in nature
Married his cousin,
Emma Wedgewood
Son Charles fell critically
ill in June, 1858
18. Evolution, Post-Darwin
Wallace sends his
manuscript – 1858
Darwin faces pressing
dilemma – to present or not
to
Darwin and Wallace present
together on July 1, 1858
Around 1900, Mendel’s
papers were “re-
discovered”, as many
scientists attempted to
merge the two theories.Alfred Russell Wallace
19.
20. On the Origin of Species (1859)
Caused controversy in religious and
scientific communities
Darwin did not use the term “evolution”
and did not suggest humans descended
from apes
Questions remained for Darwin… “The
eye to this day gives me a cold shudder...”
Theory did not gain wide acceptance until
1930s-40s
21. Premises of Natural Selection
1. Populations overproduce.
2. Resources are limited, so
competition ensues.
3. Genetic variations directly
impact the ability of
organisms to survive.
22. Premises of Natural Selection
4. Organisms with beneficial
differences will have a better
chance of survival.
5. Surviving individuals pass
their traits onto future
generations.
6. This results in a slow change
in populations over time.
23. Natural Selection
process by which
individual organisms
with favorable traits are
more likely to survive
and reproduce
IMPORTANT –
Individuals do not
evolve. Populations
evolve.
24. KEY DEFINITIONS
Population: all members of a
species in one area
Species: Group of organisms that
can produce fertile offspring
Variation: slight differences among
organisms, often caused through
genetic mutations
25. KEY DEFINITIONS
Adaptation: Trait that affords
organism a better chance of
survival
Evolution: Gradual change in a
species over time***
Adaptive Radiation: multiple
species descend from one original
species because of selection
26. Darwin’s Mechanisms for Evolution
1. Natural Selection
2. Whatever would
cause “nature” to
select for such a
ridiculous tail on this
peacock?