Timothy McDougald
Posts: 1036
Joined: Dec. 2006
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To give you another taste, these are the learning objectives from Chapter 15 Sudden Gradual Change
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D I S C O V E R I N G I N T E L L I G E N T D E S I G N
Chapter 15: Sudden, Gradual Change
Main point
Explain how the abrupt appearance of new organisms in the fossil record challenges Darwinian evolution and points to design.
Opening Chapter Question
Do you think the fossil evidence supports Darwinian evolution?
Learning Objectives
• I can explain how Darwin’s theory of evolution via descent with modification requires that
organisms evolve gradually and predicts that a large number of intermediate or transitional forms
have existed.
• I can explain that when transitional forms weren’t found, Darwin conceded that this was a serious
challenge to his theory, but then suggested that these transitional fossils were missing because the
geological record was incomplete (e.g., the “artifact hypothesis”).
• I can explain that many paleontologists recognize that missing transitional fossils are not the
product of an incomplete geological record, but rather that there are real gaps between major
taxonomic categories, and that those gaps are unlikely to be filled by future investigations.
• I can explain that the fossil record shows a pattern of extinctions (sudden disappearance of
organisms) and explosions (sudden appearance of new types of organisms) rather than a series
of transitional fossils showing gradual change from one species to the next. I understand that the
main patterns in the fossil record contradict the predictions of Darwinian evolution.
• I can describe the Cambrian explosion as a major event in the history of life, roughly 530 million
years ago, that occurred in a period of no more than about 5-10 million years, where nearly all the
major living animal phyla appeared.
• I can explain that evolutionary scientists have attempted to explain the absence of transitional
fossils in the Cambrian explosion by postulating that Precambrian fossils were too small or too softbodied
to have been preserved, and I evaluate why this explanation is problematic, because
small and soft-bodied fossils are abundant in the Cambrian explosion and are even found in
Precambrian strata (e.g., Precambrian sponge embryo fossils), though known Precambrian fossils
are not thought to be ancestors to the Cambrian phyla.
• I can list other examples of explosions in the fossil record including: (1) fish, (2) non-flowering plants,
(3) flowering plants (angiosperms), (4) mammals, (5) birds, and (6) our genus Homo.
• I can explain how scientists like Stephen Jay Gould have attempted to account for the absence
of transitional forms by invoking punctuated equilibrium, where evolution occurs in small
populations over short periods of time (too rapid for transitional forms to be fossilized), interspersed
by long periods of little change (called “stasis”).
L E A R N I N G O B J E C T I V E S
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DID | Chapter 15: Sudden, Gradual Change
• I can identify problems with punctuated equilibrium, including: (1) it requires too much genetic
change too quickly, (2) it compresses the vast majority of evolutionary change into small
populations that lived over short periods of time, thereby affording too few opportunities for
beneficial mutations to arise, and (3) it seems more like an excuse for the lack of transitional fossils
than a testable theory.
• I can explain how scientists in the field of evolutionary developmental biology (“evo devo”)
have attempted to explain how large-scale changes to a body plan could arise rapidly through
mutations in the genes controlling an organism’s development (e.g., Hox or homeobox genes).
• I can identify the problems of evolutionary developmental biology (“evo devo”) as: (1) mutations
in developmental genes (e.g., Hox genes) are typically lethal, (2) mutations in developmental
genes cannot produce new body parts but can only rearrange parts that are already present,
and (3) known examples of “evo-devo” mutations cause loss, rather than gain, of function.
• I can identify different models of change in the fossil record, including Darwinian gradual
evolution, explosions, and punctuated equilibrium
• I can discuss how only intelligent design can explain explosions of fully formed body plans in
the fossil record, as these would require rapid infusion of massive amounts of new biological
information to encode and integrate the necessary proteins, cell types, tissues, and organs to
form the new body plans.
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DID | Chapter 15: Sudden, Gradual Change
C H A P T E R O U T L I N E
I. Darwinian Gradualism
A. The hallmark of Darwinian evolution is gradual change.
B. Darwin proposed that all organisms evolved via descent with modification, and predicted that
“[t]he number of intermediate varieties, which have formerly existed on the earth, [must] be
truly enormous.”’
C. When those transitional forms weren’t found, he called it “the most obvious and gravest
objection which can be urged against my theory.”
D. A lack of fossil evidence for evolutionary transitions presents a critical and persistent problem for
materialists.
E. This lack of transition fossils challenges Materialism Tenet #7: All living organisms are related
through universal common ancestry.
F. Darwin attempted to save his theory of gradual evolution by claiming that intermediate fossils
are not found because of “the extreme imperfection of the geological record.”
G. In recent decades, however, leading paleontologists have recognized that gaps between
major taxonomic categories are not simply the result of an incomplete fossil record.
H. Rather, many of the gaps are real and are unlikely to significantly change based on new
discoveries.
I. Despite the incompleteness of the fossil record, only a tiny fraction of known fossil species are
claimed to be transitional forms.
J. The scarcity of transitional fossils is problematic for Darwinian theory.
II. Explosions in the History of Life
A. The record consistently shows a pattern where new forms come into existence abruptly, which
many have called “explosions” in the history of life.
B. A prime example of an “explosion” occurred during the Cambrian period about 530 million
years ago, when nearly all of the major living animal phyla appear in the fossil record.
C. This landmark event in the history of life is called the Cambrian explosion, and it took place
within a geological eye blink—5 to 10 million years (or possibly much less).
D. Evolutionary scientists have failed to explain the Cambrian explosion.
1. Some postulate that the Precambrian fossils were simply too small or too soft-bodied to be
preserved.
2. This explanation has severe deficiencies as small and soft-bodied organisms were commonly
fossilized. In fact, the Cambrian explosion is full of them.
3. Indeed, Precambrian sponge embryos have been discovered, demonstrating that if small
and soft-bodied transitional organisms existed, they could have been fossilized.
E. There are other examples of explosions in the fossil record.
1. Most major fish groups appear abruptly.
2. Plant biologists observe that the initial appearance of many land plants “is the terrestrial
equivalent of the much-debated Cambrian ‘explosion’ of marine faunas.”
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3. Later in the fossil record there is an explosion of flowering plants, sometimes referred to as the
“big bloom.”
4. Vertebrate paleontologists believe there was a mammal explosion with the abrupt
appearance of many orders of mammals.
5. There is also a bird explosion, with major bird groups appearing in a short time period.
6. Some have even described the abrupt origin of our own genus Homo as an explosion.
III. Punctuated Equilibrium (“Punc Eq”)
A. Because the fossil record has not confirmed Darwin’s predictions of gradual evolution,
paleontologists like Stephen Jay Gould proposed a theory where evolution takes place rapidly.
B. According to this theory, most evolution takes place in small populations over relatively short
geological time periods—too rapidly for transitional forms to be fossilized.
C. These hypothetical periods of rapid change are interspersed between long time spans without
much change, called stasis.
D. Punctuated equilibrium faces a number of problems:
1. The punc eq model requires too much genetic change too quickly.
2. It compresses the vast majority of evolutionary change into small populations that lived
during a small segment of time, allowing too few rolls of the dice for beneficial mutations to
arise.
3. Punc eq can appear to be simply an excuse for why transitional fossils are missing: Would
you believe someone who claimed to capture fairies and Leprechauns on video, but when
asked to produce the film, declares “well, they are on camera but they are too small or too
fast to be seen”?
IV. Evo Devo
A. Some evolutionists have hoped that a field called evolutionary developmental biology (“evodevo”)
could explain how large evolutionary changes could arise rapidly through mutations in
the genes controlling the development of an organism.
B. Proponents of evo-devo contend that changes to the master genes that control the
development of an organism, such as Hox or homeobox genes, can cause large, abrupt
changes in body plans.
C. Evo Devo faces various problems:
1. Developmental genes are tightly interconnected, and thus changes in one gene will affect
many others, making most mutations lethal.
2. Hox genes do not encode proteins that build body parts—they merely direct the genes that
encode body parts. Thus, Hox mutations can only rearrange parts that are already there;
they cannot create truly novel structures.
3. The best examples of evolutionary change produced by evo-devo mechanisms are meager,
and often entail loss, rather than gain of function.
DID | Chapter 15: Sudden, Gradual Change
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V. Intelligent Design and the Fossil Record.
A. The explosions of fully formed body plans in the fossil record require a cause that can rapidly
infuse massive amounts of information to encode and integrate the necessary proteins, cell
types, tissues, and organs.
B. There is only one known cause that can accomplish these tasks: intelligence.
1. Design theorists have observed that intelligent agents are uniquely capable of rapidly
infusing large amounts of information into the biosphere.
2. Only intelligence can produce the complex and specified information necessary to
coordinate many levels of organization into a functional body plan.
3. Only intelligence can conceive of a fully formed blueprint ahead of time, prior to
implementing the design in the real world.
C. The fossil record supports ID’s prediction that species might appear abruptly, indicating the
rapid infusion of new information into the natural world.
D. Design theorists have observed that intelligent agents are uniquely capable of using large
amounts of information to create blueprints, which lead to fully functional machines and new
types of organism.
DID | Chapter 15: Sudden, Gradual Change
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Church burning ebola boy
FTK: I Didn't answer your questions because it beats the hell out of me.
PaV: I suppose for me to be pried away from what I do to focus long and hard on that particular problem would take, quite honestly, hundreds of thousands of dollars to begin to pique my interest.
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