Instigator / Pro
7
1649
rating
29
debates
72.41%
won
Topic

The Fossil Record is Indicative of Biological Evolution rather than Intelligent Design

Status
Finished

All stages have been completed. The voting points distribution and the result are presented below.

Arguments points
3
3
Sources points
2
2
Spelling and grammar points
1
1
Conduct points
1
1

With 1 vote and same amount of points on both sides ...

It's a tie!
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Science
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7
1632
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20
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Description
~ 418 / 5,000

BOP is shared evenly.

Fossil Record: history of life as documented by fossils, the remains or imprints of organisms from earlier geological periods preserved in sedimentary rock.

Biological Evolution: the change in inherited traits over successive generations in populations of organisms.

Intelligent Design: the theory that life cannot have arisen by chance and was designed and created by some intelligent entity.

Round 1
Pro
  Thank you for accepting this debate. The fossil record is overwhelmingly indicative of biological evolution, rather than intelligent design. The existence of fossils and analysis of fossil morphology prove that biological evolution has taken place by being indicative exclusively of biological evolution, rather than intelligent design. My opponent must, by virtue of his position on the resolution, assume the insurmountable burden of demonstrating that for one, fossils indicate that there are things in nature that are intentionally designed; and for two, that that Designer is intelligent. 

  To begin, the fact that fossils exist indicate that there were different organisms in the past. If there exist individual organisms that have been fossilized, they presumably originated from a population of similar organisms. It is a fact that populations produce offspring whose traits are different from their ancestors'. That change is evolution taking place. From this basis, it follows to propose the hypothesis that these ancient populations are ancestral to the living populations of today. 

  To test this hypothesis, one may analyze the morphological traits of these older organisms. In horses, the Pliohippus [1], Dinohippus[2], and Equus[3], all appear to be descended from the one before, respectively. The pre-orbital fossae of Pliohippus are deep, in Dinohippus, these facial depressions are shallow, while in Equus, the fossae are non-existent. A rudimentary form of the "stay apparatus" in modern horses, that allows them to conserve energy while standing for extended periods first takes shape in the Dinohippus fossils, further indicating an ancestral relationship between their populations. 

  This model of common ancestry makes testable predictions. For example, the model predicts that if tetrapods are descended from lobe finned fish, then there should be an intermediate fossil, that ought to appear in a specific layer of the geologic column, between the earliest known tetrapods, and older lobe-finned fish [4]. When paleontologists excavated the site where the fossil was predicted to be, if common ancestry were true, they found exactly what they were looking for in Tiktaalik [5]. Tiktaalik was a species whose morphology was transitional between the aforementioned [6], and it was found where, in the geological age strata, it was predicted to be in. 

  In conclusion, the fossil record is indicative of biological evolution, rather than intelligent design. The fact that fossils of ancient organisms exist indicates that populations may be ancestral to one another. The smooth transition of morphological traits in fossils such as apparent horse ancestors indicates a change in populations over successive generations, leading to the emergence of morphologically different descendent populations. Finally, this model can make novel, testable predictions about future data, which have been confirmed to be true. This model has met the highest standard of scientific rigor in this regard. 

  To finish, I will ask two questions to my opponent:
1) What novel, testable prediction has intelligent design made that has been confirmed to be true?
2) If you were to attempt to falsify or confirm the hypothesis that species X was ancestral to species Y, and you had only their bones and the knowledge that X is older than Y, what (morphological) traits would you look for?
Con
As we discuss whether the fossil record is indicative of biological evolution or intelligent design, I think we need to be clear on what we are talking about. What my opponent and I will not disagree on is that populations of animals can undergo small changes through successive generations. What we will disagree about is that all life forms can be traced back to a single common ancestor through these small changes. I do not believe we can take an observable process such as adaptation or speciation, and assume that we can extrapolate these changes all the way back to a common ancestor. That is the claim of evolution that I will be arguing against in this debate as it relates to the fossil record.

The Cambrian Explosion
One of the greatest challenges to the Theory of Evolution has been from the fossils found within the Cambrian layer. In particular, the timeframe known as the Cambrian explosion provides some evidence that is unexpected from a Darwinian viewpoint:

(1) the sudden appearance of Cambrian animal forms;
(2) an absence of transitional intermediate fossils connecting the Cambrian animals to simpler Precambrian forms; 
(3) a startling array of completely novel animal forms with novel body plans; and
(4) a pattern in which radical differences in form in the fossil record arise before more minor, small-scale diversification and variations.[1]

The Cambrian explosion is called such because the vast number of "novel animal forms with novel body plans" seem to just appear out of nowhere. Even if one uses rock-dating methods that assume the Cambrian explosion happened within the span of less than 10 million years, the mechanism of gradual change proposed by evolutionists cannot account for such disparate body structures. There is simply not enough time.

The pre-Cambrian layer offers little to no help for this problem. The gap between the few organisms found in the pre-Cambrian and the explosion of organisms found in the Cambrian explosion does not seem to be explainable by the mechanisms of evolution (gradual changes over time). The image and description found in Figure 2.8 provides an illustration of this.[2] As Stephen Jay Gould explains in his book Wonderful Life, we can distinguish between small and large-scale differences with the terms diversity and disparity.[3] Diversity would refer to small-scale differences, such as those between different species of similar animals. Disparity would refer to large-scale differences between animals with completely different body plans.

If the general mechanism of evolution is gradual changes over time leading to greater biodiversity, it would make sense that changes in diversity (small-scale) would happen first, which would accumulate over long-periods of time creating disparity (large-scale). But this is not the case in the Cambrian explosion. Gould states, "Using this terminology, we may acknowledge a central and surprising fact of life's history - marked decrease in disparity followed by an outstanding increase in diversity within the few surviving designs." [4]

Another study puts it even more clearly, “The fossil record suggests that the major pulse of diversification of phyla occurs before that of classes, classes before that of orders, orders before that of families...The higher taxa do not seem to have diverged through an accumulation of lower taxa.” [5]

The mechanism of gradual changes over time that is proposed by evolutionists does not match what we see.

Intelligent Design
While critique of a scientific theory without proposing an alternative is a valid approach in the scientific process, it is not enough if we want to arrive at true knowledge of the world around us. Intelligent design is a broad theory that encompasses different views on a spectrum, much like evolution. But the core idea is "that certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection." [6] This is quite similar to the definition provided in the debate description, but it highlights where the conflict between intelligent design and evolution lies.

I will wait until Round 2 for rebuttals, including answering the questions given by PRO in Round 1. I will also delve more deeply into intelligent design as it relates to the fossil record. But one of the main aspects of intelligent design is specified complexity - the idea that life forms are highly complex and organized in a specified way that is best explained by an intelligent cause.

Sources
Round 2
Pro
  Thank you for your response. 

  The only argument in favor of intelligent design presented was "that life forms are highly complex and organized in a specified way that is best explained by an intelligent cause." My opponent has not however, made the case for how an intelligent designer caused complex organisms to come about. He has not demonstrated that a designer even exists, let alone that the designer is intelligent, or has created the animals that were fossilized. He flatly asserts that an intelligent cause best explains complexity and specification, but he does not explain why. Complexity does not imply intention. 

 The primary methodology for elevating a mere hypothesis to a theory is that the hypothesis can make novel, testable predictions about future data. The hypothesis that "ancient populations are ancestral to the living populations of today," has met this standard by being both indicated by more recent fossils, such as the transition from Pliohippus to the modern Equus, and, by predicting and discovering a transitional form between the earliest known tetrapods and older lobe finned fish in exactly the geologic layer and geographical region that the theory predicted. 

  The Cambrian explosion does not challenge the claim that modern organisms are descended from common ancestors. Being a period of around 30 million years [2], the term "explosion" can be misleading. That isn't very long in geologic time, but evolution can cause dramatic changes in very short time spans, such as the change of Siberian Silver Foxes. In 1959, Russian scientists began breeding domesticated Siberian foxes out of a wild population for the sake of the animals' beautiful silver coats. As the scientists selectively bred the foxes for tameness, the foxes unexpectedly underwent morphological changes such as a shorter, rounded snout, the loss of their silver coats, floppy ears, and curly tails [4]. My opponent accepts upfront, short-term evolution, because that's the evolution that he can't deny. But to deny the logical conclusion of that concession is to accept the centimeter, and deny the meter. What the silver fox experiment demonstrates is that a selective pressure, such as humans wanting tame foxes, can produce tons of other morphological changes in a very short time. Evolution can happen rapidly, even in less than 100 years. With 30 million years, it is not unreasonable to expect morphological changes in organisms.

  It's important to keep in mind that most cambrian and precambrian animals were soft bodied, meaning they would not be easily fossilized. So the "suddenness" of the appearance of novel body forms in the fossil record is likely a side effect of the fossil record's incompleteness. However, even though soft bodied organisms do not often fossilize, we still have a number of precambrian fossils of Vendian Fauna [3]. 

  Fossils found in the middle Cambrian layer, such as the Burgess shale, have been dated to between 505 and 510 million years old [1]. This means the Cambrian explosion occurred much farther back than my opponent has alluded. In addition, a number of body plans that we see both preceding, and persisting after the Cambrian persist into the modern day, such as arthropods[4], sponges[5], and cnidarians[6]. Sponge fossils have been dated as far back as 760 million years ago, with their lineages persevering into and beyond the Cambrian.

  "If the general mechanism of evolution is gradual changes over time leading to greater biodiversity, it would make sense that changes in diversity (small-scale) would happen first, which would accumulate over long-periods of time creating disparity (large-scale). "
  The basic body structures that work, such as being a vertebrate, or a tetrapod, are going to act as foundations for the diversification of more superficial traits. In the short term, things like fur color, eye color, and other more surface level changes take place, but they always take place within the confines of the animal's ancestry, and build onto the body plan already there. In the Cambrian, many novel body plans start to fossilize for us to see, but they were simple structures, such as coelomates [7], whose only defining feature is having a body cavity to store the organs in. A tetrapod doesn't stop being a vertebrate, but a tetrapod is a "novel body plan" that descends directly from vertebrates. We, as descended from coelomates, are still that, but we are also eukaryotes, which came before coelomates, and we are tetrapods, which came after. 

  In conclusion, Evolution is overwhelmingly supported by the fossil record, while intelligent design has not been indicated by any fact brought up thus far. The Cambrian explosion is not a challenge to the claim of evolution, and in fact actually supports it. The theory of evolution can, unlike intelligent design, meet the criteria of testable predictions about novel future data. It is a reliable model and the only model indicated by the fossil record. 
Con
This round will mostly feature rebuttals.

Horses
The sources provided with each horse genus also gave estimated dates when they lived:
  • Pliohippus: 12-6 million years ago
  • Dinohippus: 13-5 million years ago
  • Equus: according to other sources, at least 3.5 million years ago-present day[1]
That is quite a large spread. It should also be noted that we have seen practically no evidence linking these different horses together in an evolutionary chain. Read PRO's argument again.

To test this hypothesis, one may analyze the morphological traits of these older organisms. In horses, the Pliohippus, Dinohippus, and Equus, all appear to be descended from the one before, respectively. The pre-orbital fossae of Pliohippus are deep, in Dinohippus, these facial depressions are shallow, while in Equus, the fossae are non-existent.

A few note-worthy points:
  • We have not seen where the specific fossils were found, or if they are even from the same continent.
  • We have not seen how old the specific fossils are that are being linked, especially since there is a time gap in the millions of years to choose from.
  • Related to the previous point, we have not seen the specific layer that the fossil evidence was found in.
  • We have not been told why a slight change in the depression of a single bone in the skull somehow shows an ancestral lineage of horses.
  • We have not been told why a slight change in the depression of a single skull bone should be considered evidence of macroevolution.
Not all of these points necessarily have to be answered. I have raised them to show that we have not been given a convincing argument that supports the debate resolution. But here is the second point made by PRO:

A rudimentary form of the "stay apparatus" in modern horses, that allows them to conserve energy while standing for extended periods first takes shape in the Dinohippus fossils, further indicating an ancestral relationship between their populations.

This is an assertion. We have not been given any explanation as to why this statement is true.


Tiktaalik
The finding of a Tiktaalik fossil is certainly an interesting discovery. However, it would be helpful to be able to examine the specimen more closely to verify the claim being made that it is a transitional fossil.

Could you please provide a link that shows the femur of Tiktaalik so we can observationally confirm that it actually had the features of a tetrapod?

This article explains how the earliest fossil footprints of tetrapods on land have been dated around 395 million years ago [2]. The article is based on a publication that has restricted access, but the information can be verified from the abstract regarding dating.[3] Your source from Round 1 states:

We know the lobe-finned fish are from 390-380 million year old rocks. The first tetrapods appear around 363 million years ago. Common sense tells us that the transitional form must have arisen 380-363 million years ago.[4]

Could you please explain how Tiktaalik, which is supposedly 380-363 million years old, confirms any transitional prediction if tetrapods were already walking on land 395 million years ago.


Extrapolation
A statement from my opponent in Round 2:

My opponent accepts upfront, short-term evolution, because that's the evolution that he can't deny. But to deny the logical conclusion of that concession is to accept the centimeter, and deny the meter. What the silver fox experiment demonstrates is that a selective pressure, such as humans wanting tame foxes, can produce tons of other morphological changes in a very short time. Evolution can happen rapidly, even in less than 100 years. With 30 million years, it is not unreasonable to expect morphological changes in organisms.

The reason I accept "short-term evolution" is because it can be directly observed. I can see the morphological changes in Silver Foxes with no assumption needed. However, I cannot observe fish turning into land animals. That requires the assumption of extrapolation rather than observation. Extrapolation can be a useful tool, but it is ultimately a prediction or a guess, even if it is an educated one. I prefer the scientific method of observation over extrapolation. That is why I accept "short-term evolution."


Testable Predictions of Intelligent Design
One of the fundamental aspects of the Theory of Evolution is that organisms came about through an unguided and progressive process. This is antithetical to Intelligent Design, which is based on the view that life came about by guided processes. This difference is an obvious place to go to look for predictions. A prediction that goes against the notion of unguided processes would seem to favor guided processes as it's logical conclusion.

One of the main predictions of Intelligent Design came, surprisingly, from Charles Darwin himself in his book The Origin of the Species, “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.”

While the technical name of "Irreducible Complexity" did not begin here, the very concept was expressed by Darwin, and it is an example of a testable prediction in the framework of Intelligent Design. He understood that if it could be demonstrated that a biological structure could not be said to have arisen by natural processes, one must conclude the structure came about by the guidance of an intelligent designer. This would disprove evolution and favor Intelligent Design.

One example is the transport system in a cell. Of course, the fossil record is not a great place to go for a discussion on cellular transport systems.


Cambrian Explosion
My opponent stated this in Round 2:

It's important to keep in mind that most cambrian and precambrian animals were soft bodied, meaning they would not be easily fossilized. So the 'suddenness' of the appearance of novel body forms in the fossil record is likely a side effect of the fossil record's incompleteness. However, even though soft bodied organisms do not often fossilize, we still have a number of precambrian fossils of Vendian Fauna.

If most Cambrian and Precambrian animals were soft-bodied, then why are there so many of these soft-bodied animals fossilized in the Cambrian layer, but so few fossils prior to the Cambrian layer?

It should be noted that the Cambrian explosion is not synonymous with the Cambrian layer. While there may be varying opinions on exactly how long of a time period it was, there seems to be a general consensus that it consists of a time period of less that 10 million years. My opponent confirmed this in Round 2 by stating, "Fossils found in the middle Cambrian layer, such as the Burgess shale, have been dated to between 505 and 510 million years old."

PRO has not addressed the main problem of the Cambrian. I will restate part of my argument from Round 1:

Diversity would refer to small-scale differences, such as those between different species of similar animals. Disparity would refer to large-scale differences between animals with completely different body plans.

If the general mechanism of evolution is gradual changes over time leading to greater biodiversity, it would make sense that changes in diversity (small-scale) would happen first, which would accumulate over long-periods of time creating disparity (large-scale). But this is not the case in the Cambrian explosion. Gould states, "Using this terminology, we may acknowledge a central and surprising fact of life's history - marked decrease in disparity followed by an outstanding increase in diversity within the few surviving designs." [5]

Another study puts it even more clearly, “The fossil record suggests that the major pulse of diversification of phyla occurs before that of classes, classes before that of orders, orders before that of families...The higher taxa do not seem to have diverged through an accumulation of lower taxa.”[6]

Seemingly out of nowhere, we have an explosion of novel body plans in the Cambrian. These novel body plans (large-scale disparities) start to show more small-scale changes (diversity). This is contradictory to the idea of Gradualism, and has been challenged by the proposition of Punctuated Equilibria. My opponent has not addressed how gradual changes over time can address the explosion of novel body plans in the Cambrian. There is a clear inconsistency in the actual mechanism of macroevolution and the rate at which it takes place.


Sources
Round 3
Pro
  Thank you for your response. 

  The stay apparatus and the skull depressions are just two of a wealth [1] of physical traits that transition smoothly through the horse lineage.

  The stay apparatus first appears in dinohippus fossils [2]. There is a more advanced form of this apparatus in modern horses [3]. This, in addition to the gradual disappearance of the pre-orbital fossae, are exclusively indicative of biological evolution rather than intelligent design. 

  "Could you please provide a link that shows the femur of Tiktaalik so we can observationally confirm that it actually had the features of a tetrapod?"
  This link has good pictures of Tiktaalik fossils, including the pelvis and fins [4].

  Of course tiktaalik is not ancestral to all living tetrapods. The oldest tetrapod fossils my opponent has mentioned are trace fossils of footprints. Even if the exact time of when tetrapods arose is earlier than the age of the tiktaalik fossils we have, the point is that the model predicted, with the available data, that there should be an animal in a specific age layer, with specific transitional features. This was exactly what was found. 

  Pre-cambrian animals were mostly soft bodied and did not fossilize well. The animals that fossilized in the Cambrian were overwhelmingly hard bodied, such as trilobites [5].

  Most animals don't fossilize, and the few that do, will be overwhelmingly hard bodied. That's what we see in the cambrian, the arrival of more hard body plans in the fossils.

  My opponent attempts to juxtapose punctuated equilibrium with gradualism, but the reality is that they are two way of looking at the same phenomenon. Paleontologists see punctuated equilibrium in the fossil record because of the incompleteness of the fossil record. But these "long periods of stasis" and "sudden explosions" are over periods of geologic time, millions of years. That rate of change maps perfectly well onto gradualist models.

  "The reason I accept "short-term evolution" is because it can be directly observed. I can see the morphological changes in Silver Foxes with no assumption needed. However, I cannot observe fish turning into land animals. That requires the assumption of extrapolation rather than observation. Extrapolation can be a useful tool, but it is ultimately a prediction or a guess, even if it is an educated one. I prefer the scientific method of observation over extrapolation. That is why I accept "short-term evolution.""
  The scientific method requires testable predictions, which I fulfilled with the tiktaalik example. The confirmed testable predictions mean that macroevolutionary changes are supported by the fossil record. The silver fox example is demonstrative of how quickly evolution can produce drastic morphological changes. My opponent is accepting the centimeter and denying the meter. 

"While the technical name of "Irreducible Complexity" did not begin here, the very concept was expressed by Darwin, and it is an example of a testable prediction in the framework of Intelligent Design."
  "No true examples of irreducible complexity have ever been found" [7].

"One example is the transport system in a cell."
  From the abstract: "Although the bacterial proteins function in simple assemblies, relatively little mutation would be required to convert them to function as a protein transport machine. This analysis of protein transport provides a blueprint for the evolution of cellular machinery in general" [6]. 

  The above study details a process by which the transport system very well could have evolved. In the spirit of keeping with the theme of the debate, I would be interested to discuss an alleged example of irreducible in the fossil record.

  It is notable that my opponent only answered one of the two direct questions I posed in the first round. I request that my opponent answer the other, and equally important question: "If you were to attempt to falsify or confirm the hypothesis that species X was ancestral to species Y, and you had only their bones and the knowledge that X is older than Y, what (morphological) traits would you look for?" In this case, we will Substitute X for dinohippus and Y for the modern Equus. 

  In conclusion, the only evidence presented in this debate has been indicative of biological evolution. There has been given no evidence provided that a designer exists, that the designer is intelligent, or that anything in the fossil record is indicative of having been designed by this designer.
Con
Horses
 The stay apparatus and the skull depressions are just two of a wealth [1] of physical traits that transition smoothly through the horse lineage.
This is an assertion with a link to a Wikipedia article. No argument has been presented regarding physical traits other than the stay apparatus and the skull depression. Here are the points that I raised in the previous round:
  • We have not seen where the specific fossils were found, or if they are even from the same continent.
  • We have not seen how old the specific fossils are that are being linked, especially since there is a time gap in the millions of years to choose from.
  • Related to the previous point, we have not seen the specific layer that the fossil evidence was found in.
  • We have not been told why a slight change in the depression of a single bone in the skull somehow shows an ancestral lineage of horses.
  • We have not been told why a slight change in the depression of a single skull bone should be considered evidence of macroevolution.

While I did not ask these as questions needing answers, I had hoped for at least some interaction to help us understand how these slight morphological differences are indicative of evolution from a single common ancestor. It is uncontroversial to say there are differences from one horse species to another. We can see that today. But I fail to see how a small variation in a single skull bone over the course of millions of years in fossils from various continents is evidence that horses evolved from fish.

In conclusion, the only thing that these horse fossils show is that there are differences within the horse species. Variations within family groups are not contradictory to the Theory of Intelligent Design.

Tiktaalik
The Prediction
Here is what PRO originally stated the prediction was in Round 1:
For example, the model predicts that if tetrapods are descended from lobe finned fish, then there should be an intermediate fossil, that ought to appear in a specific layer of the geologic column, between the earliest known tetrapods, and older lobe-finned fish.

Here is the direct statement from PRO's original source:
We know the lobe-finned fish are from 390-380 million year old rocks. The first tetrapods appear around 363 million years ago. Common sense tells us that the transitional form must have arisen 380-363 million years ago.[https://tiktaalik.uchicago.edu/searching4Tik2.html]

I should note that we have not actually been shown any citation that shows the prediction was made prior to the finding of the Tiktaalik fossil. If this is supposed to be a true prediction, we should be able to have some sort of evidence with a timestamp that this "prediction" was not simply made after the fossil was found.

It has not been disputed that fossil tracks from fully formed tetrapods were dated from 395 million years ago. Yet PRO's source claims "lobe-finned fish are from 390-380 million year old rocks." There seems to be a timeline issue since evidence of tetrapods can be found prior to the time of lobe-finned fish. Recall that the alleged prediction, as stated by PRO in Round 1, was that tetrapods are descended from lobe-finned fish. But PRO's source seems to state that lobe-finned fish did not exist until after tetrapods had already been walking around on land. If this is true, then tetrapods could not have descended from lobe-finned fish.

The Fossil
We have been told that Tiktaalik is an intermediate fossil between lobe-finned fish and tetrapods. Besides the prediction failing due to timeline issues, there is a glaring assumption that has been made. We have no observable proof that Tiktaalik had four limbs. It must be assumed that Tiktaalik had features similar to a tetrapod (four limbs) because we do not have a femur fossil to examine. Until we can actually observe a femur fossil, we are left having to guess what the alleged "legs" look like. If PRO cannot provide observable proof of the actual limbs that Tiktaalik is said to have had, then we should at least wait until more evidence arises before we start making assertions. Assuming conclusions to be indisputable fact without any direct observational proof is bad science.

In conclusion, PRO's argument that Tiktaalik provides evolutionists with an example of a testable prediction fails on all fronts. We have no citations showing the prediction was made prior to the finding of the fossil. The prediction failed to produce an accurate evolutionary timeline showing that tetrapods descended from lobe-finned fish. We also have no observable proof that Tiktaalik shared the morphology of a tetrapod.

The Cambrian Explosion
I feel it is important to stay focused on the key differences between the two positions in this debate. My opponent is arguing that the fossil record supports the idea that all life came about through a single common ancestor, by means of changes in inherited traits over successive generations in populations of organisms. This form of evolution must be extremely gradual because large scale changes, or macromutations, would almost always be detrimental or fatal.

When asked why the Cambrian layer seems to exhibit an explosion of biological disparity with no ancestral lines, my opponent stated in Round 3:
Pre-cambrian animals were mostly soft bodied and did not fossilize well. The animals that fossilized in the Cambrian were overwhelmingly hard bodied, such as trilobites
If this is true, where are the hard-bodied ancestors? Shouldn't there be slowly evolving hard-body fossils throughout the Pre-Cambrian and Cambrian layers? But that's not what we see. Rather, there is a massive number of hard-bodied fossils - as well as soft-bodied ones - that seem to come out of nowhere with no ancestral lines.

My position in this debate is that the fossil record is better explained by Intelligent Design. Random gradual changes through inherited traits cannot explain how so many novel body plans appear as if from nowhere. The amount of genetic information required for this cannot be explained by random mutations. This was the point of my argument about punctuated equilibrium and gradualism. And contrary to what my opponent has asserted, there is a difference and they are not compatible. Gradualism requires steady gradual changes over long periods of time. Punctuated Equilibrium posits small periods of major change with long periods of stagnancy between them. Those are two different mechanisms driving the evolution. 

Punctuated Equilibrium was conceived of because the fossils, particularly those in the Cambrian layer, do not support the idea of continual and gradual changes over time. This was the point of quoting Stephen Jay Gould on diversity and disparity. This point has been dismissed by denying the differences that obviously exist between them. I will refer to my Round 1 argument on this matter that we should see small amounts of diversity leading to greater disparity over time. But instead, we see great disparity followed by diversity. This is not what one would expect to see via evolution from a single common ancestor.

Irreducible Complexity
Note that this debate is not about proving whether Evolution or Intelligent Design are true. We are discussing which seems better supported by the fossil record. But my opponent gave this critique:
The above study details a process by which the transport system very well could have evolved. 
Notice the phrase, "very well could have evolved." That seems to indicate a hypothesis or a theory, not an observable, testable, repeatable conclusion. If it can actually be demonstrated that this would happen via the scientific method, that would certainly be a devastating blow to the concept of Irreducible Complexity.

Question
If you were to attempt to falsify or confirm the hypothesis that species X was ancestral to species Y, and you had only their bones and the knowledge that X is older than Y, what (morphological) traits would you look for?
This seems to be your hypothesis. If that is so, you should be the one determining how to falsify it. Morphological traits are not conclusive to determine whether one specimen is ancestral to another, especially when you are looking at fossils. They can look similar and be completely unrelated.
Round 4
Pro
Sorry Fruit, but I'm not going to be able to post an argument in time. Please consider my last argument as my closing.
Con
Horses and Tiktaalik
Since there were no further arguments, I will refer readers to my rebuttals in Round 3. I do want to make one more mention of my opponent's appeal to extrapolation for scientific knowledge, and the argument concerning Tiktaalik is a perfect example.

It was asserted that Tiktaalik is an ancestral species to tetrapods based on its morphology. Yet that assertion is not based on observable proof of a complete fossil. A partial fossil with no femur was used to assume that Tiktaalik had four leg-like limbs. The basis of this conclusion is not the scientific method, which would involve waiting until an actual femur fossil was found before making such a conclusion. Rather, the basis was extrapolation - a guess. It may be an educated guess, but without the hard evidence it is still a guess.

When my opponent asserts that I am denying the logical conclusion of a slight change in horse bones over time to be proof that horses evolved from fish, he is using the same process of extrapolation. I do not think it is irrational to base my scientific conclusions on an extrapolation as my opponent is trying to do in this particular argument.

The Cambrian Explosion
We did not see much interaction on this point besides a simple denial of there being any problem presented by the Cambrian Explosion. Here were the four points I presented in Round 1 providing unexpected evidence from a Darwinian standpoint:

(1) the sudden appearance of Cambrian animal forms;
(2) an absence of transitional intermediate fossils connecting the Cambrian animals to simpler Precambrian forms; 
(3) a startling array of completely novel animal forms with novel body plans; and
(4) a pattern in which radical differences in form in the fossil record arise before more minor, small-scale diversification and variations.[1]

My opponent argued that this should be expected because soft-bodied animals don't fossilize easily. My defense was that even if that were true, there should be an ancestral line of hard-bodied fossils leading up to the Cambrian. But there is no such line. If hard-bodied animals do fossilize well, we should see many of those ancestral lines. But we see no such evidence.

Conclusion
To restate from Round 3, my position in this debate is that the fossil record is better explained by Intelligent Design. Random gradual changes through inherited traits cannot explain how so many novel body plans appear as if from nowhere. The amount of genetic information required for this cannot be explained by random mutations.

Sources