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Discovering Evolution.
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Lecture I. Introduction.
Readings: Young, Ch. 1; Johnston. On the Importance of Darwin;
As referenced in text.
I. Introduction.
A. Most scientists believe the question of evolution settled.
1. Significant segments of society nonetheless reject this
conclusion – hence the “Evolution Wars.”
2. To characterize doubters / skeptics as “morons” unhelpful
– see Bloom (2005).
a. Poisons the well of civil discourse.
b. Discourages objective consideration of what evolution
can and cannot explain.
3. Stakes are enormous.
a. Evolution arguably most important principle in biology.
b. Humanity’s view of itself – “Why are we here?” – inextricably bound up with “How we came to be.”
B. This class: We consider what the theory of evolution is
and how it came to be.
1. The second question inevitably leads us to consider
how science works.
2. We will also discuss the connection of scientific inquiry
generally to broader societal issues.
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II. The Wisdom of God Manifested in the Works of Creation.
A. The Judeo-Christian tradition encouraged the study of
the Nature as a way of studying God.
“The concept of a created world gave grounds for regarding nature as orderly and open to rational inquiry. The
study of nature could be acknowledged and respected as
the study of God’s handiwork … .” – David Young. The
Discovery of Evolution.
B. The resulting studies led to replacement of Design by Descent with Modification. Compare
1. Paley’s “Teleological Argument.” (1800) vs.
2. Darwin-Wallace paper (1858).
C. Eiseley (p. 198) argues that triumph of Darwinism does not
rule out all forms of the design argument and is therefore
compatible with certain kinds of religion.
”The evolutionists discovered that ‘nature makes things that
make themselves’ and thus succeeded in apparently removing the need of a Master Craftsman. … it was only later that
the question began to be asked: Why does nature let things
make themselves?
D. One answer is the Second Law of Thermodynamics:
organized states of matter that don’t reproduce must
eventually disappear. But that only begs the point.
Why the Second Law?
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III. Science as the Modeler’s Art.
A. Models are simplified representations of reality.
1. Can be mathematical, pictorial or verbal.
2. Reduce real world complexity to “the essentials.”
B. All theories are models, and
they must be falsifiable.
C. From mechanistic assumptions,
one deduces predictions that
can then be tested.
Figure 1. Science as the modeler’s art.
Mechanistic assumptions and simplifying
approximations inform the construction of
a model that generates predictions. Falsification results when observation contradicts prediction (red slashes) or when
new observations indicate assumptions
or simplifications to be untenable (blue
slashes).
D. Model falsification results if
1. Observation ≠ prediction.
2. Assumptions and / or simplifying approximations turn out to
be wrong or inappropriate.
E. Model acceptance results when repeated attempts at falsification fail.
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F. Important:
1. A model can be falsified but never be proved.
2. .Revising a model in light of new information is not the same
thing as confirming its predictions.
3. What results is a simply a new model, the predictions of
which must then be subject to further experimental test.
G. All models – even large scale simulations, e.g., climate models
– reduce real-world complexity to a manageable approximation.
1. Simplification essential if models are to be useful – see Borges (1998).
2. “All-but-the-kitchen-sink” simulations replace systems that
aren’t understood with models that can’t be understood – at
least not mathematically.
a. The best one can do is to perform (numerical) experiments.
b. Over abundant computing power a temptation of modernity.
3. Real world complexity a source of confusion: Is predictionobservation conflict the result of
a. Inappropriate mechanistic assumptions?
b. Inappropriate simplifications?
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H. Macroscopic vs. microscopic
levels of organization.
1. Classic example is derivation of the gas law,
PV = kT
from a model of molecular
collision.
2. Here,
a. P, V, and T are macroscopic quantities.
b. Molecular velocities are
microscopic variables.
Figure 2. Science at small and large length
scales. A microscopic model generates macroscopic predictions. As in Figure 1, red and
blue slashes indicate model falsification and
need for revision.
3. In case of evolution,
a. Gene frequencies are the
microscopic variables;
b. Their alteration by mutation, migration, selection,
drift, etc., microscopic
processes.
c. History of life, patterns of
diversity and phylogenetic
branching, the macroscopic observables
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Figure 3. Evolution according to the
“modern synthesis.”
IV. Two Theories of Evolution.
A. Descent with modification (DwM) – the observable pattern;
the processes that produce it – the responsible mechanisms.
B. Regarding DwM:
1. Supporting evidence has been accumulating since before
Darwin.
2. Seeking “God in the gaps” a fool’s errand.
C. Regarding Mechanisms:
1. A succession of theories: Lamarck, Darwin-Wallace, Modern Synthesis, Post-Modern Synthesis.
2. Each informed by discoveries that invalidated previous assumptions and by independent opinion as to how the universe operates.
D. No one has deduced the pattern from the mechanism.
1. In terms of Figures 1 and 2, we have never gone round
the loop in the large.
2. With regard to the “Modern Synthesis,” recent advances in genetics and development suggest that we
never could.
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E. Contrasting Views:
1. “Nature, to cite a modern cliche, always bats last. She will not
succumb to the simplicities of our hopes or mental foibles, but
she remains eminently comprehensible. Evolution follows the
syncopated drumbeats of complex and contingent histories,
shaped by the vagaries and uniquenesses of time, place, and
environment. Simple laws with predictable outcomes cannot
fully describe the pageant and pathways of life.” – S. J. Gould
(1999b).
Problem: Post-facto comprehension ≠ à priori prediction.
2. “The primary problem with the synthesis is that its makers established natural selection as the director of adaptive evolution
by eliminating competing explanations, not by providing evidence that natural selection among ‘random’ mutations could,
or did, account for observed adaptation.” (Leigh, 1999).
3. “Microevolution, … while arguably consistent with larger scale
patterns, does not predict them in detail. Variation plus selection does not, for example, predict that during the first 4 billion
years of earth’s history, i.e., most of it, the dominant organisms
were microbes. It does not predict the skeletization, if not the
emergence, of the major taxonomic groups some half a billion
years ago. Nor does it necessitate the dominance of early
Paleozoic seas by invertebrates, nor the subsequent colonization of land by insects and the limbed descendants of rhipid8
istian lungfish. It cannot tell us that dinosaurs and mammals
would come into being at about the same time, and, with regard
to the 100 million year eclipse of the latter by the former, it says
nothing. It is unable to tell us what would have transpired had
the Chicxulub asteroid missed. And, of course, it cannot predict
the emergence of man, much less the fact that humans would
one day compose symphonies and argue as to whether or not
God really does play dice with the universe.”
F. When challenged, evolutionists are always more comfortable
defending the pattern.
1. “Whether the naturalist believes in the views given by Lamarck, or Geoffroy St.-Hilaire, by the author of the 'Vestiges,'
by Mr. Wallace and myself, or in any other such view, signifies
extremely little in comparison with the admission that species
have descended from other species and have not been created immutable; for he who admits this as a great truth has a
wide field opened to him for further inquiry.” – Darwin
(1863a).
2. “to learn that the same set of 25,000 to 30,000 genes is present in most animals. Almost every gene in our DNA has a
homologous gene in the DNA of other mammals, such as the
mouse. It is even more extraordinary when we look at more
distantly related organisms; the invertebrate sea squirt, for
example, has only half our number of genes, but as many as
two-thirds of these have homologues in human DNA.” – J. D.
Watson (2005).
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3. “The evidence for common descent … is independent of specific gradualistic explanatory mechanisms. None of the dozens of predictions [discussed herein] directly address how
macroevolution has occurred … . None … assumes that natural selection is valid [or] … that natural selection is sufficient for
generating adaptations or the differences between species … .
Because of this evidentiary independence, the validity of the
macroevolutionary conclusion does not depend on whether
natural selection, or the inheritance of acquired characters, or
a force vitale, or something else is the true mechanism of
adaptive evolutionary change. The scientific case for common
descent stands, regardless.” – Theobald (2004).
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Figure 6. Evolution of whales from artiodactyl-like ancestors. From “Walking with Whales.”
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G. Darwin’s Facts.
1. “The view given by me on the origin or derivation of species
… connects … by an intelligible thread of reasoning a multitude of facts.”
a. “Formation of domestic races by man's selection,”
b. “The classification and affinities of all organic beings,”
c. “The innumerable gradations in structure and instincts,“
d. “The similarity of pattern in the hand, wing or paddle of
animals of the same great class,”
e. “The existence of organs become rudimentary by disuse,”
f. “The similarity of an embryonic reptile, bird and mammal,
with the retention of traces of an apparatus fitted for
aquatic respiration;”
g. “The retention in the young calf of incisor teeth in the upper jaw, &c.,”
h. “The distribution of animals and plants, and their mutual
affinities within the same region, – their general geological
succession, and the close relationship of the fossils in
closely consecutive formations and within the same country; extinct marsupials having preceded living marsupials
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in Australia, and armadillo-like animals having preceded
and generated armadilloes [sic] in South America,”
i. “Many other phenomena, such as the gradual extinction of old forms and their gradual replacement by
new forms better fitted for their new conditions in
the struggle for life.” – Darwin (1863b)
2. Note that
a. Only the first and last relate to selection.
b. The last – gradual extinction and replacement – was and
remains a pious hope.
H. Some proposed evolutionary mechanisms have been, or
at least are believed to have been, falsified. E.g.,
1. Lamarck’s “Power of Life” – predicts massive parallelism – not observed.
2. Inheritance of acquired characters – segregation of
germ cells and soma. In the process of resurrection by
“transgenerational epigenetic effects?”
3. Orthogenesis and racial senescence – “bushiness”
evolution / no known mechanism.
4. Result was the “Modern Synthesis.”
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V.
Plausibility and Expectations.
A. Simplicity. Triumph of Darwinism was due principally to
the fact that it offered a more economical explanation for
emerging patterns of distribution and development, for the
existence of homologous and vestigial organs, for adaptation and mal-adaptation, etc., than did the alternative theory
of Special Creation.
“… what would the Astronomer say to the doctrine that the
planets moved [not] according to the law of gravitation, but
from the Creator having willed each separate planet to move
in its particular orbit?” – Darwin (1842).
B. Mechanism.
1. Continental Drift proposed to explain geographical distribution
of extinct species.
2. Initially rejected for
lack of a plausible
mechanism.
3. Discovery of sea-floor
spreading proved Wegener had been right
after all.
Figure 4. Distribution of fossil Mesosaurus
and other Permo-Triassic genera. The major
landmasses are shown as they existed in relation to each other prior to the break-up of the
super-continent of Pangea. The simplest explanation of such patterns is that the continents were assembled into a single landmass,
as first proposed by Wegener [w15]. From
http://de.wikipedia.org/wiki/Mesosaurier.
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C. Experience.
1. Lyell correctly rejected Lamarck’s theory of spontaneous generation of unicells based on previous falsification of the hypothesis in case of lower plants and
insects.
2. His belief that Paleozoic mammals and birds would
eventually be discovered (i.e., as more fossil-bearing
formations became available) proved wrong.
D. World View.
1. Charles Lyell’s belief
that earth’s history was
entirely explicable in
terms of “actual causes.”
a. Accepted for over
100 years.
b. Destroyed once and
for all by discovery
of iridium at Gubbio.
2. Lamarck’s belief that
species evolved because
Nature wouldn’t permit
extinction.
Figure 5. Iridium spike at Gubbio, Italy,
provided 1st convincing support for termination of the Mesozoic by bolide impact.
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3. Scientific worldviews can reflect both “known facts”
and beliefs from outside of science.
1. Evolutionists like to point to the religious motivations of evolutionary skeptics.
2. But history teaches that there are other sources of
ideological input.
a. Lysenkoism.
b. Eugenics
3. Science in the service of ideology usually results in
bad science and bad policy.
E. Facts Themselves Evolve.
1. Kelvin’s estimates (vs. Darwin’s assumed requirements) of
the age of the earth suggest that when different intellectual
starting points lead to vastly different conclusions, something undiscovered may be waiting in the wings.
2. The attempts of geologists to harmonize their estimates
with Kelvin’s maximum grant of 100 m.y. also merits consideration – see Powell (2001; Chapter 1).
a. “Facts” arrived at via the same iterative process of model
formulation and testing described above.
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VI. Wrap-Up.
A. Evolution a central biological concept with implications that
extend far beyond biology.
B. Theory of evolution the unexpected consequence of trying to
understand God’s Nature by studying His Creation.
C. Theories are models that can be falsified but never proved.
D. Some theories deduce macroscopic behavior from microscopic models.
E. There are two theories of evolution.
1. Descent with modification – the pattern.
2. Mechanism that produces the pattern.
F. Evidence for DwM overwhelming.
G. Ideas as to mechanism continue to evolve.
H. The evolution of scientific theories results from a complex interaction of theory and observation modulated by experience,
philosophy and societal inputs.
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