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Giants of Geology
A. R. Wallace
Charles Darwin
Charles Lyell
William Smith
James Hutton
Nicola Steno
Robert Hooke
1600
1650
1700
1750
1800
1850
1900
1950
Chapter 3. Evolution
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Charles Darwin & Natural Selection
Evidence of evolution – the fossil record
Mechanism of evolution – DNA
A modification - Punctuated Equilibrium
Creationism – a formidable opponent
Chapter 3. Evolution





Charles Darwin & Natural
Selection
Evidence of evolution – the fossil
record
Mechanism of evolution – DNA
A modification - Punctuated Equilibrium
Creationism – a formidable opponent
“the father of evolutionary biology “
Darwin at age 68 in 1877
The Voyage of H.M.S. Beagle

1831 December
27 Tuesday
(about 11:00 AM)
After a few delays,
H.M.S. Beagle
headed out from
Plymouth with a
crew of 73 under
clear skies and a
good wind. Darwin
became sea-sick
almost immediately.
Darwin at age 31 in 1840
theory of natural selection

Darwin was not the first
person to consider that life
on this planet evolved, but
he was the first to come up
with a viable working
mechanism on how it
happened.
1854 December
At last Darwin figured out how
populations split off into
separate species. Using the
industrial revolution as a
metaphor, he saw that
populations of animals, like
industry, expand and specialize
to fit into niches with
competition acting as the
driving force. He saw nature as
the ultimate "factory." However,
Darwin preferred not to make
much of this metaphor because
it seemed to depend more on
economic principles rather than
pure science.
http://www.aboutdarwin.com/timeline/time_06.html#0080
Darwin at age 45 in 1854
A. E. Wallace – Darwin’s Equal?

1858 June 18
Darwin received a paper from Alfred Russel
Wallace, who was still at the Malay
Archipelago. The paper was titled: "On the
Tendency of Varieties to Depart Indefinitely
from the Original Type." Darwin was
shocked! Wallace had come up with a
theory of natural selection that was very
similar to his own. The paper contained
concepts like "the struggle for existence,"
and "the transmutation of species."
Upon further examination Darwin saw that
Wallace had some ideas about natural
selection that he did not agree with. For one
thing, Wallace tried to mix social morality
with natural selection, proposing an upward
evolution of human morals which would
eventually lead to a socialist utopia
(Darwin's natural selection had no goal).
What's more, Wallace believed that
cooperation in groups aided in the progress
of mankind (Darwin saw natural selection as
being influenced by competition). Finally,
Wallace's natural selection was guided by a
higher spiritual power (there was no divine
intervention in Darwin's version).
Alfred Russel Wallace in
1848, age 25
"On the Origin of Species by
means of Natural Selection."

1859 November 22
"Origin of Species" went
on sale to the public
today at a price of 15
shillings. 1,250 copies
were printed, most of
which sold the first day.
It was an immediate
success and Darwin
started the same day
editing the work for a
second edition.
First Edition of “Origin of Species”
Examples of Natural Selection
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Darwin's Finches
Darwin's finches are an excellent example of
the way in which species' gene pools have
adapted in order for long term survival via
their offspring. The Darwin's Finches
diagram illustrates the way the finch has
adapted to take advantage of feeding in
different ecological niche's.
Their beaks have evolved over time to be
best suited to their function. For example,
the finches who eat grubs have a thin
extended beak to poke into holes in the
ground and extract the grubs. Finches who
eat buds and fruit would be less successful
at doing this, while their claw like beaks can
grind down their food and thus give them a
selective advantage in circumstances where
buds are the only real food source for
finches.
Examples of Natural Selection
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Industrial Melanism
Polymorphism pertains to the existence of
two distinctly different groups of a species
that still belong to the same species. Alleles
for these organisms over time are governed
by the theory of natural selection, and over
this time the genetic differences between
groups in different environments soon
become apparent, as in the case of
industrial melanism.
Industrial melanism occurs in a species
called the peppered moth, where the
occurrence has become of more frequent
occurrence since the beginning of the
industrial age. The following argument
elaborates the basis of principles involved in
natural selection as far as industrial
melanism is concerned.
Pollution, which is more common in today's
world since the industrial age causes a
change in environment, particularly in the
1800's when soot would collect on the sides
of buildings from chimneys and industries
and make them a darker color.
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The resultant effect was that the peppered
moth, which had a light appearance was
more visible against the darker backgrounds
of sooty buildings.
This meant that predators of the peppered
moth could find them more easily as they
are more visible against a dark background.
Due to mutations, a new strain of peppered
moth came to existence, where their
phenotype was darker than that of the
white peppered moth.
This meant that these new, darker peppered
moths were once again harder to track
down by their prey in environments where
industry has taken its toll.
In this instance, natural selection would
favor the darker moths in polluted
environments and the whiter moths in the
lesser polluted environments due to their
ability to merge in with their environmental
colors and lessen the chances of them being
prone to a predator.
http://www.biology-online.org/2/11_natural_selection.htm
Examples of Natural Selection

Sickle Cell Trait

Consider this argument of natural selection in the case of sickle cell trait, a genetic defect common in
Africa.
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Sickle cell trait is a situation that occurs in the presence of a recessive allele coding for haemoglobin, a
substance in the blood responsible for the transport of gases like oxygen. The presence of the allele is
either partially expressed recessively (sickle cell), or fully expressed by a complete recessive expression
which results in full blown anaemia. If this particular allele is dominant, no sickle cell trait is expressed in
the phenotype.
The above occurrences in the case of a recessive allele result in structural defects of red blood cells,
severely reducing the organisms capacity to uptake oxygen. It was pointed out that in Africa, there is a
high frequency of this mutation, where cases of malaria were high. A substantiated link was made noting
those who suffer sickle cell trait or anaemia were immune to the effects of malaria.
This is yet again natural selection at work. Although sickle cell trait or anaemia are not advantageous
characteristics on their own, they prove to be advantageous in areas where malaria proves to be a greater
threat to preserving the genome (i.e. surviving). The incomplete dominance of this genetic expression
proves favourable either way. This is how science has understood natural selection since the first studies
involving Darwin. In

http://www.biology-online.org/2/11_natural_selection.htm
WHAT IS EVOLUTION?
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Most non-scientists seem to be
quite confused about precise
definitions of biological
evolution.
When discussing evolution it is
important to distinguish
between the existence of
evolution and various theories
about the mechanism of
evolution.
WHAT IS EVOLUTION?

One of the most respected evolutionary biologists has defined biological
evolution as follows:
"In the broadest sense, evolution is merely change, and so is all-pervasive;
galaxies, languages, and political systems all evolve.
Biological evolution ... is change in the properties of populations of
organisms that transcend the lifetime of a single individual.
The ontogeny of an individual is not considered evolution; individual
organisms do not evolve. The changes in populations that are considered
evolutionary are those that are inheritable via the genetic material from one
generation to the next. Biological evolution may be slight or substantial; it
embraces everything from slight changes in the proportion of different
alleles within a population (such as those determining blood types) to the
successive alterations that led from the earliest protoorganism to snails,
bees, giraffes, and dandelions." - Douglas J. Futuyma in Evolutionary
Biology, Sinauer Associates 1986
http://www.talkorigins.org/faqs/evolution-definition.html
WHAT IS EVOLUTION?

It is important to note that biological evolution refers to populations
and not to individuals and that the changes must be passed on to the
next generation. In practice this means that,
Evolution is a process that results in heritable changes in a population
spread over many generations.
This is a good working scientific definition of evolution; one that can be
used to distinguish between evolution and similar changes that are not
evolution.
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Another common short definition of evolution can be found in many
textbooks:
"In fact, evolution can be precisely defined as any change in the
frequency of alleles within a gene pool from one generation to the
next." – (Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth
Publishers, p.974 )
Meaning of ALLELE

Definition: [n] one of two alternate
forms of a gene that can have the
same locus on homologous
chromosomes and are responsible
for alternative traits; "some alleles
are dominant over others"
Evolution (cont.)

When biologists say that they have
observed evolution, they mean that
they have detected a change in the
frequency of genes in a population.
POOR DEFINITIONS
The Oxford Concise Science Dictionary:
"evolution: The gradual process by which the present diversity of plant and animal
life arose from the earliest and most primitive organisms, which is believed to
have been continuing for the past 3000 million years."
This is poor because not only does this definition exclude prokaryotes, protozoa,
and fungi, but it specifically includes a term "gradual process" which should not
be part of the definition.
More importantly the definition seems to refer more to the history of evolution than
to evolution itself. Using this definition it is possible to debate whether evolution
is still occurring.
Also, this definition provides no easy way of distinguishing evolution from other
processes. For example, is the increase in height among Caucasians over the
past several hundred years an example of evolution? Are the color changes in
the peppered moth population examples of evolution?
DEFINITION (CONT.)

“Recently I read a statement from a creationist who claimed
that scientists are being dishonest when they talk about
evolution. This person believed that evolution was being
misrepresented to the public. The real problem is that the
public, and creationists, do not understand what evolution is all
about. This person's definition of evolution was very different
from the common scientific definition and as a consequence he
was unable to understand what evolutionary biology really
meant. This is the same person who claimed that one could not
"believe" in evolution and still be religious! But once we realize
that evolution is simply "a process that results in heritable
changes in a population spread over many generations" it seems
a little silly to pretend that this excludes religion! “

Laurence Moran , January 22, 1993
Laurence Moran , January 22, 1993, http://www.talkorigins.org/faqs/evolution-definition.html
BAD DEFINITIONS
Standard dictionaries are even
worse:
"evolution: ...the doctrine according
to which higher forms of life
have gradually arisen out of
lower.." - Chambers
"evolution: ...the development of a
species, organism, or organ
from its original or primitive
state to its present or
specialized state; phylogeny or
ontogeny" - Webster's
These definitions are simply wrong.
Unfortunately it is common for
non-scientists to enter into a
discussion about evolution with
such a definition in mind. This
often leads to fruitless debate
since the experts are thinking
about evolution from a different
perspective. When someone
claims that they don't believe in
evolution they cannot be
referring to an acceptable
scientific definition of evolution
because that would be denying
something which is easy to
demonstrate. It would be like
saying that they don't believe in
gravity!
Chapter 3. Evolution





Charles Darwin & Natural Selection
Evidence of evolution – the fossil record
Mechanism of evolution – DNA
A modification - Punctuated Equilibrium
Creationism – a formidable opponent
Fossils
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Evolution is a fact, not a theory
Evidence comes from the fossil record,
but also from biology, anthropology
What is the fossil evidence? Petrified
remains of earlier life that records
systematic changes
Fossil hominid skulls – missing
links no longer missing?
Some of the figures have been modified for ease of comparison Smithsonian Institution.)
Fossil hominid skulls.
(A) Pan troglodytes, chimpanzee, modern
(B) Australopithecus africanus, STS 5, 2.6 My
(C) Australopithecus africanus, STS 71, 2.5 My
(D) Homo habilis, KNM-ER 1813, 1.9 My
(E) Homo habilis, OH24, 1.8 My
(F) Homo rudolfensis, KNM-ER 1470, 1.8 My
(G) Homo erectus, Dmanisi cranium D2700,
1.75 My
(H) Homo ergaster (early H. erectus), KNM-ER
3733, 1.75 My
(I) Homo heidelbergensis, "Rhodesia man,"
300,000 - 125,000 y
(J) Homo sapiens neanderthalensis, La
Ferrassie 1, 70,000 y
(K) Homo sapiens neanderthalensis, La
Chappelle-aux-Saints, 60,000 y
(L) Homo sapiens neanderthalensis, Le
Moustier, 45,000 y
(M) Homo sapiens sapiens, Cro-Magnon I,
30,000 y
(N) Homo sapiens sapiens, modern
EVIDENCE OF EVOLUTION
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The best arguments for evolution include:
Branching organization of life
Homology
Vestigial structures and imperfections
Embryonic history
Biogeography
Fig. 3.5
EVIDENCE FOR EVOLUTION 1.
Branching organization of life.
The branching pattern of life is indicated by changes
(mutations) in the molecule cytochrome c. The molecule
is very similar in humans and apes, but progressively
different in other species. Distance between nodes is
proportional to measured change.
Homology of forelimbs of various
vertebrates, similar bones have
similar colors. Although the functions
are different the bones are
structurally similar and develop from
similar embryonic tissues. Simplest
explanation is that all evolved from a
common ancestor, the lobe-finned
fish.
EVIDENCE FOR EVOLUTION
2. Homology
Homology: organs with different functions
are built with same basic parts.
C. Panda’s thumb. Their true
thumb has fused into a digit,
but because they need a
functional thumb, a modified
wrist bone serves as one. A
classic example of an
imperfection.
EVIDENCE FOR EVOLUTION 3.
Vestigal structures and imperfections
A. Splint bones in horses, serve no useful function and
are in fact detrimental, since breaking one can hobble a
horse for life. Both a vestige and imperfection.
B. Pelvic and thigh bones in whales and snakes serve no
purpose but show that both once had functional hind
limbs.
EVIDENCE FOR EVOLUTION 4.
Embryonic history
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Next slide: Ernst Haeckel’s famous depiction of embryos at
various stages of development. Early stages are remarkably
similar regardless of adult form. Note presence of gill slits and
similarity of vertebral column (backbone).
Why should such similarities exist if all did not have a common
ancestor?
Also good example of Nature’s parsimony: once a useful
structure has been developed, use it again and again. See also
“Homology” example of vertebrate forelimbs.
Fig. 3.8
EVIDENCE FOR EVOLUTION 5.
Biogeography.
Ecological parallelism between
Australian pouched mammals
(marsupials) and placental mammal
counterparts. Marsupials and placentals
diverged over 100 Ma but similar
ecological niches on different continents
caused these very different groups of
mammals to converge on similar body
shapes.
This is a good example of environmental
pressures steering evolution toward
body types that can exploit the niche.
Note that nature did not recreate the
exact same body type, keeping with the
rule-of-thumb that the same species has
never been recreated.
Branching Organization of Life
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The Tree of Life: Another powerful argument
in favor of evolution
In Darwin’s time, the “tree of life” was
deduced from anatomical similarities
In our time, DNA proves striking proof not
only for the tree of life but also as a
mechanism of evolution
Haeckel’s Evolutionary Tree

A tree-like
representation by Ernst
Haeckel, a nineteenthcentury evolutionary
biologist.
Ernst Heinrich Phillip
August Haeckel, from The
Evolution of Man (1879)
•
http://www.learner.org/channel/courses/biology/archive/images/1198_d.html
STANDARD PHYLOGENTIC TREE
Human Fossil Bush
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The "Hominid Family
Bush" made up of
modern humans,
their ancestors, and
their now-extinct
relatives.
http://www.learner.org/channel/courses/biology/archive/animations/stills/as_humev2.html
Five-kingdom vs. threedomain tree of life
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•
The older fivekingdom tree of life,
which has been
replaced by Woese's
three-domain tree.
http://www.learner.org/channel/courses/biology/archive/images/1957.html
Tree of Life— Lateral Gene
Transfer Diagram
Revised Tree of Life with all groups divided into their domains. Includes information about lateral gene
transfer and the endosymbiosis of bacteria that became mitochondria and chloroplasts.
http://www.learner.org/channel/courses/biology/archive/animations/stills/as_compev7.html
Chapter 3. Evolution





Charles Darwin & Natural Selection
Evidence of evolution – the fossil record
Mechanism of evolution – DNA
A modification - Punctuated Equilibrium
Creationism – a formidable antagonist
DNA

Instructions that provide almost all of the
information necessary for a living organism to
grow and function are in the nucleus of every
cell. These instructions tell the cell what role it
will play in your body. The instructions are in
the form of a molecule called deoxyribonucleic
acid, or DNA . DNA is the chemical
responsible for preserving, copying and
transmitting information within cells and from
generation to generation. In humans, the DNA
molecule consists of two ribbon-like strands
that wrap around each other, resembling a
twisted ladder. This is often described as a
double helix. DNA is contained in tightly coiled
packets called chromosomes , found in the
nucleus of every cell. Chromosomes consist of
the double helix of DNA wrapped around
proteins. The twisted ladder is made up of
repeating units called nucleotides , each of
which is a single building block...
What really happened …
Chapter 3. Evolution





Charles Darwin & Natural Selection
Evidence of evolution – the fossil record
Mechanism of evolution – DNA
A modification - Punctuated
Equilibrium
Creationism – a formidable opponent
Micro & Macro Evolution
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
Throughout most of the last century,
researchers primarily focused on
microevolution , which is slight genetic
change over a few generations in a
population. Until recently, it was thought
that these gradual changes from generation
to generation indicated that past species
regularly evolved gradually into other
species over millions of years.
This model of long term gradual change is
usually referred to as phyletic gradualism. It
is essentially the 19th century Darwinian
idea that species evolve slowly at a more or
less steady rate. A natural consequence of
this sort of macroevolution would be the
slow progressive change of one species into
the next in a line.
phyletic gradualism
(macroevolution)
Punctuated Equilibrium

In the early 1970's, Stephen
J. Gould and Niles Eldredge
argued that there is sufficient
fossil evidence to show that
some species remained
essentially the same for
millions of years and then
underwent short periods of
very rapid, major
change. Gould coined the
term “punctuated
equilibrium”
Punctuated equilibrium
Punctuated Equilibrium

The punctuated, or rapid change,
periods were presumably the result
of major environmental changes in
predation pressure, food supply,
climate, etc. During these times,
natural selection can favor varieties
that were previously at a
comparative disadvantage. The
result can be an accelerated rate of
change in gene pool frequencies in
the direction of the varieties that
become the most favored by the
new environmental conditions. It
would be expected that long
droughts, major volcanic eruptions,
and the beginning and ending of ice
ages would be likely triggers for
rapid evolution.
Long periods of stability and
short episodes of change
Origin of Species

Where do new species come from? That is a
key question that the biological sciences have
been asking for more than 200 years. Charles
Darwin provided part of the answer in his
explanation of natural selection. The
remainder came as a result of Gregor Mendel's
experiments with basic genetic inheritance
and the 20th century discoveries of the other
natural processes that can cause
evolution. We now know that evolution can
occur in two different patterns--adaptive
radiation into multiple species and successive
speciation within a single evolutionary line.
 http://anthro.palomar.edu/synthetic/synth_9.htm
Adaptive
radiation

Adaptive radiation is the progressive
diversification of a species into two or
more species as groups adapt to
different environments.
Natural selection is usually the
principle mechanism driving adaptive
radiation.
The initial step is the separation of a
species into distinct breeding
populations. This usually happens as a
result of geographic or social
isolation. Over time, the gene pools of
the isolated populations diverge from
each other by gradually acquiring
different random mutations and
sometimes as a result of random
genetic drift. When the populations
are in dissimilar environments,
environmental stresses are often not
the same.
Adaptive radiation
As a result, nature selects for
different traits existing within the gene
pools of the populations. Over time,
the populations genetically diverge
enough so that they can no longer
reproduce with each other. At this
point, they have become separate
species and usually continue to
diverge in subsequent generations. In
intermediate stages, the two newly or
about to be separated species may be
able to interbreed and produce
children, but most of them are likely to
be sterile. This is the case with the
offspring of horses and donkeys--i.e.,
mules. Eventually, however, species
genetically diverge so much that they
are unable to produce any
children. This is the case with sheep
and cattle.
successive speciation

The evolution of species by
successive speciation occurs within
a single evolutionary line without
the branching of adaptive
radiation. This takes place when
the members of a species consist of
a single breeding population for
many generations. Descendant
generations experience continuous
spontaneous mutations and new
directions of natural selection as
the environment changes.

This results in progressive changes
in the gene pool frequencies of the
population. At any one time, all
members of the population are the
same species. However, as
generations subsequently replace
each other, the gene pool is
transformed--i.e., it evolves.
 Successive speciation
within a single species line
Eventually, the changes are great
enough that if descendants could go
back in time to mate with their distant
ancestors, the genetic differences
would prevent them from producing
fertile offspring. In other words, they
would be different species.
Chapter 3. Evolution





Charles Darwin & Natural Selection
Evidence of evolution – the fossil record
Mechanism of evolution – DNA
A modification - Punctuated Equilibrium
Creationism – a formidable
opponent
Creationist History
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1910-1915 A set of Christian tracts emerged in the US
which took a literalistic interpretation of Genesis (ex nihlo
creation).
1920-1968 Evolution banned from public schools
1963 Creation Research Society, Institute for Creation
Research
1970-1980 "Equal Time"
1978-1995 "Balanced Treatment"
1996 "Evolution as Theory“
2000 “Intelligent Design”
Notes on “theory “
Definition: [n] a theory that explains scientific
observations; scientific theories must be
falsifiable

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A systematically organized body of knowledge
applicable in a relatively wide variety of
circumstances, especially a system of
assumptions, accepted principles, and rules of
procedure devised to analyze, predict, or
otherwise explain the nature or behavior of a
specified set of phenomena.
Abstract reasoning; speculation.
theory
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n 1: a well-substantiated explanation of some aspect
of the natural world; an organized system of
accepted knowledge that applies in a variety of
circumstances to explain a specific set of
phenomena; "theories can incorporate facts and laws
and tested hypotheses"; "true in fact and theory"
2: a tentative theory about the natural world; a
concept that is not yet verified but that if true would
explain certain facts or phenomena; "a scientific
hypothesis that survives experimental testing
becomes a scientific theory";
theory
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A set of statements or principles devised to
explain a group of facts or phenomena,
especially one that has been repeatedly
tested or is widely accepted and can be used
to make predictions about natural
phenomena.
Abstract reasoning; speculation: a decision
based on experience rather than theory.
An assumption based on limited information
or knowledge; a conjecture.