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New Limbs from Old Fins, Part 2: Comparative Anatomy

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September 16, 2011 Tags: History of Life

Today's entry was written by Stephen Matheson. Please note the views expressed here are those of the author, not necessarily of The BioLogos Foundation. You can read more about what we believe here.

In the previous post in this series, we looked at the remarkable blueprint that underlies all limbs – one bone, two bones, blobs, digits – and considered some ways we might explain it. One potential explanation is, roughly speaking, design. Perhaps the blueprint represents an idea or preference in the mind of the Creator. Perhaps the blueprint represents an optimized design, one so superior that there is no better way to build a limb. The other potential explanation is common ancestry. The blueprint was present in ancestors of the distant past, and it has been retained with modification in all tetrapod vertebrates that have descended from those pioneering ancestors. We noted that one explanation need not entirely preclude the other.

In the rest of the series, we will look closely at the evolutionary explanation for the blueprint. That explanation postulates that tetrapod limbs arose during a particular era in life's history, and that they arose as modifications of the fins of fish. And the evolutionary explanation isn't just an interesting idea. It's a comprehensive explanation – it helps us to understand bones, fossils, genes, chemical signaling systems. It provides a coherent framework for understanding why limbs are the way they are, and how they got that way.

Comparing the anatomy of tetrapod vertebrates and fish

The idea that tetrapods arose from fish is not new; E.D. Cope proposed in 1892 that tetrapods descended from lobe-finned fish. (Modern lobe-finned fishes include coelacanths and lungfish, and comprise one of two divisions of the bony fishes. The other division, the ray-finned fishes, includes most familiar kinds of fish.) In the early days, biologists inferred ancestral relationships between species largely through comparative anatomy and embryology: they would carefully classify organisms according to their structure (including their structure during development) and look for relationships that generated nested hierarchies. A simple nested hierarchy goes something like this: 1) animals with backbones; 2) animals with backbones and limbs; and 3) animals with backbones, limbs, and hair. Animals in group 3 also belong to groups 1 and 2, while animals in group 2 also belong to group 1, and so the groups together define a nested hierarchy. Such studies alone could have led some scientists to infer an ancestral relationship between fish and tetrapods, and perhaps those studies did convince them. But then there were fossils of various types of fish and other vertebrates, many long extinct. That fossil record was relatively sketchy in 1892, but it nevertheless led Cope and others to conclude that certain fish had given rise to tetrapods at a particular time in natural history.

The fossil record shows a fish-to-tetrapod transition

Here are some basic findings from the fossil record that suggest a fish-to-tetrapod transition and that have been known for decades:

  • Fish, including fish with bones, lived on the earth before tetrapods appeared. Specifically, fossils of bony fish first appear in rocks from about 420 million years ago.

  • Tetrapods appear in the fossil record at a particular point in history and then persist and diversify in subsequent eons. Their arrival was long thought to have occurred about 365 million years ago, although some recent findings have challenged that hypothesis.

  • Tetrapods that still had some fishy features were prowling the planet 365 million years ago.

  • Lobe-finned fish that were starting to look more like tetrapods were eating other fish about 385 million years ago.

Even many decades ago, there were hints that something interesting happened between 400 million years ago and 365 million years ago. Let's take a close look at the ancient animals that suggest the fish-to-tetrapod transition.

Ancient animals

The most primitive known tetrapods for which we have skeletal remains lived 365 million years ago. They were undeniably tetrapods, but there was definitely something fishy about them. (Heh heh.) One of the most famous of these creatures is Acanthostega, discovered in 1987 by British paleontologist Jennifer Clack and pictured below. Acanthostega is a card-carrying tetrapod, with fingers and toes. But it has a fish tail, with fin rays. Another well-known primitive tetrapod is Ichthyostega, which lived around the same time as Acanthostega. Like Acanthostega, it is a true tetrapod, but has several odd fish-like structural features. For example, its skull is more fish-like than that of Acanthostega. In summary, both Acanthostega and Ichthyostega already used the limb blueprint, even though both also had some fish-like anatomical characteristics. Their presence 365 million years ago shows that tetrapods must be at least that old, and their mixture of anatomical features suggests that the transition happened not long before that.

And what about the lobe-finned fish that looked a bit tetrapod-ish? That animal is Panderichthys, described as “vaguely crocodile-shaped” with skeletal features that were tetrapod-like. Specifically, this ancient fish had tetrapod-like “shoulders,” and recent analysis found some finger-like bones at the ends of the fins. The creature also had a breathing hole on the top of its head. These fish lived around 385 million years ago.

The hunt for the earliest tetrapods

Taken together, these observations suggested that the fish-to-tetrapod transition occurred between 385 and 365 million years ago. Eager to see what that transition looked like, scientists began to look for 375 million-year-old rocks in which they might find animals at the beginning of tetrapod-hood. They wanted to catch evolution in the act.

Let's stop and think about this, because it's cool and because it's important to note the extent to which evolutionary biology is hypothesis-driven. Critics of evolution sometimes portray the theory as an untestable historical conjecture, depicting it as fundamentally different from experimental science in the lab. But the hunt for the earliest tetrapods was an effort to test a hypothesis that had generated a prediction. Based on the hypothesis that lobe-finned fish were ancestors of tetrapods, scientists predicted that intermediate animals, “fishapods,” would be found in the gap between Panderichthys and Acanthostega. To evaluate the prediction, all they needed to do was find some suitable 375 million-year-old rocks.

Neil Shubin describes that search in the first chapter of Your Inner Fish. He and his colleagues found suitable rocks in the islands of the Arctic: the right age, nicely exposed (by erosion), and representative of the kind of environment that their quarry would frequent – freshwater streams. They made their biggest discovery on their last trip (“a do-or-die situation”) in 2004. That discovery was Tiktaalik roseae, the “fishapod.”

The “fishapod”

Tiktaalik roseae is one of the most extraordinary fossil intermediates ever described, and its public debut in 2006 was front-page news. An artist's conception of the animal is pictured below.

There are several aspects of the anatomy of Tiktaalik that earn it the title “fishapod.” Like a good fish, it had scales and webbed fins. Like a tetrapod (more specifically, like a crocodile), it had a flat head, with eyes on the top of the head, and it had a neck. But what about those fins? Or are they limbs? Remarkably, the answer seems to be, “both.”

The fins of Tiktaalik were part fish fin, part tetrapod limb. On the outside, they looked like fins, with webbing. On the inside, though, these fins were clearly tetrapod-like. Amazingly, the fins of Tiktaalik were built using a primitive version of the limb blueprint: one bone, two bones, blobs, digits. As Shubin writes in Your Inner Fish, “We had a fish with a wrist.” (The Tiktaalik roseae web site at the University of Chicago is a great source for images and more information.)

Let's address three questions about Tiktaalik that might have occurred to you. First, why might animals like Tiktaalik have developed tetrapod-like fins? Shubin and his colleagues suggest that these limb-like fins may have been useful for doing “push-ups” in the shallow water. (Like Panderichthys, Tiktaalik had a breathing hole on top of its head and was clearly adapted for living and moving in shallow water.) Second, is Tiktaalik an ancestor of all tetrapods? No, not necessarily. What Tiktaalik shows us is that animals were developing tetrapod features in the context of fish bodies, and Tiktaalik shows us the context (shallow water) in which this likely occurred. But that doesn't mean that our lineage arose from Tiktaalik itself. Finally, is Tiktaalik now the oldest tetrapod? No, apparently not. For one thing, Tiktaalik is truly transitional, and probably therefore not worthy of full tetrapod membership. But more notably, data published in 2010 show that tetrapods are a lot older than was thought at the time of Tiktaalik's discovery. The new findings show footprints that are unmistakably those of a tetrapod, in rocks about 395 million years old. Surprisingly, then, tetrapods were already on their way long before Neil Shubin's specimen lived. Tiktaalik is truly a fish/tetrapod intermediate, which was living at the same time as animals that were fully tetrapods. A simple story of succession, in which intermediates disappear and are replaced by less intermediate types, seems to be an oversimplification.

In conclusion, the fossil record provides evidence that the fins of fish and the limbs of tetrapods are related by ancestry: limbs seem to be modified versions of fins. What other evidence supports this proposal? In the next post, we will turn to developmental biology, and explore the meaning of the term 'homology.'

Further reading:

Neil Shubin (2009) Your Inner Fish: A Journey Into the 3.5-Billion-Year History of the Human Body. New York: Vintage Books.

Carl Zimmer (2006) A Fin is a Limb is a Wing: How Evolution Fashioned its Masterworks. Online at NationalGeographic.com.

Tiktaalik roseae website at the University of Chicago.

Jennifer Clack's website at the University of Cambridge.

Images are from Wikipedia.


Stephen Matheson is an author, editor, and developmental cell biologist, formerly at Calvin College in Grand Rapids, Michigan. He writes regularly on his blog “Quintessence of Dust”, which explores issues of science and Christian faith, focusing on genetics, development, evolution, neuroscience, and related topics, regularly discussing intelligent design, creationism, and other scientific issues that worry evangelical Christians.

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glsi - #64807

September 18th 2011

It’s been a while since I read Shubin’s book, but one of the things I recall is his claim that he knew in advance the type of transitionary fossil he was looking for and where he might find it based upon the age of the rock formations he thought would contain it.

If that’s the case, then why not also find the immediate ancestor of Tiktaalik as well as the immediate successor?  I suppose the first needs to be just slightly more like a fish and the later just a bit more of a land animal.

If this is an important transitionary species then why not show it in the “flip-book” of evolution that Dennis Venema discusses in his most recent post?  



beaglelady - #64810

September 18th 2011

Science takes a lot of money and time and even more hard work. Even after a fossil is found and transported to a lab it can takes months of work for a preparator to extract it from the matrix in which it is embedded.  For all we know, there might be other grant proposals in the works to look for similar fossils. 


John - #64811

September 19th 2011

My dear gisi,


I’m skeptical that you ever read Shubin’s book, as he makes it very clear that we are talking about a metaphorical tree here.

“If that’s the case, then why not also find the immediate ancestor of Tiktaalik as well as the immediate successor?  I suppose the first needs to be just slightly more like a fish and the later just a bit more of a land animal.”

Because the branches of trees split, as Shubin makes clear and Darwin made clear. 

My hypothesis is that the straw man of portraying evolution as a metaphorical ladder, in which one species (or even more insanely, a much larger phylogenetic group) morphs into another, instead of a metaphorical tree is absolutely essential to protect the falsehoods of IDCreationism from critical analysis.

What do you think, gisi?

sfmatheson - #64809

September 18th 2011

It would be really great to have many millions more fossils, but to see the pattern of shared ancestry we have more than enough. A fish with a wrist is an animal that links tetrapod limbs to fish, and that’s an observation that a comprehensive scientific explanation (like common descent) must account for.

As for the flip book, I’m sure you know that Dennis wasn’t describing the fossil record. But it’s common for paleontologists to illustrate evolutionary change in illustrations like the one linked below. It’s a bit flip-book-like, but it does have the potential to mislead people into thinking that tetrapod evolution was akin to ascending a ladder, with each intermediate succeeding the previous one. Given recent evidence that tetrapods are somewhat older than Tiktaalik (link below), as I noted in the last paragraph of my post, I think we should be more careful with ladder-like images.

Tetrapod evolution diagram: http://tinyurl.com/3fxtkk4

Tetrapods may be older than Tiktaalik: http://tinyurl.com/ye9mguu


Argon - #64821

September 19th 2011

Just an aside: Foraminifera are well fossilized, accumulate in great numbers and are present across the world. And guess what they reveal… Common descent with variation and clear paths of ancestry.



glsi - #64825

September 19th 2011

Well, if you’ve ever wondered why the majority of the general public does not believe in evolution, this would be a prime example.  You’ve got a star example of a “transitionary” fossil but what does it connect?  Nothing to nothing.  It’s sheer speculation and very unconvincing at that.


It’s not a matter of a lack of fossils.  There are truck loads of them.  It’s just that they don’t show evolution.  They show stasis.  It’s widely known by all, but for some reason not accepted by some.  

But if Tiktaalik is too old and hard to find it’s relatives, how about something modern like the giraffe?  Let’s see some “almost-giraffe” fossils.

beaglelady - #64849

September 20th 2011

Are you really interested in giraffes? Do you want to learn more? What is the creationist claim for the origin of the giraffe?


Ashe - #64828

September 19th 2011

Ever heard of Bohlinia


glsi - #64838

September 19th 2011

Ever read about them?  If so I’m sure you know that there must be hundreds of missing Darwinian transitionary species which are needed to arrive at the modern giraffe.


Here’s Stephen Jay Gould on the subject:  ”...ancestral species are relatively short necked, and the spotty evidence gives no insight into how the long-necked modern species arose”
“The standard story, in fact, is both fatuous and unsupported.”

I’m surprised you even bring such stuff up.  Once again, the majority of people have no trouble seeing the enormous problem Darwinism has with the lack of supportive evidence for the theory.  

beaglelady - #64850

September 20th 2011

What is the source of your Stephen Jay Gould quote? (Of course it isn’t from creationist material!)


Ashe - #64853

September 20th 2011

Gould was referring to the standard explanation for giraffe neck evolution when he said “both fatuous and unsupported”, ie that it is not necessarily true that the selective advantage was being able to get at higher food sources.


John - #64882

September 21st 2011

“Ever read about them?”


No, the question was whether you’ve heard of them, which is then followed by the question of whether you’ve evaluated the evidence for yourself instead of resorting to hearsay.

“If so I’m sure you know that there must be hundreds of missing Darwinian transitionary species which are needed to arrive at the modern giraffe.”

I’m sure we can all see your equivocation between missing fossils and missing species. The more interesting question is, can you?

We are missing fossils of passenger pigeons. Does that tell you that they never existed?
br>
“Here’s Stephen Jay Gould on the subject:  ”...The standard story, in fact, is both fatuous and unsupported.”
br>
And what’s the antecedent of “the standard story” from Gould’s essay, gisi?
br>
“Once again, the majority of people have no trouble seeing the enormous problem Darwinism has with the lack of supportive evidence for the theory.”
br>
Yet all of your posts are evidence-free, and you are pretty explicitly intending to deceive when you try to fool your readers into thinking that “Darwinism” is the antecedent.
br>
Why are you so afraid of evidence, gisi? Why all rhetoric, and deceptive rhetoric at that?
br>
Where’s YOUR faith? Why do you keep pretending that you are familiar with the evidence?

Terrance - #64829

September 19th 2011

Glsi,

Much of the fossil record might show ‘stasis’ but it is still packed full of transitional fossils. You do realise that right?

You want relatives of Tiktaalik? How about Eusthenopteron, Panderichthys, Elginerpeton, Ventastega, Metaxygnathus, Acanthostega, Icthyostega, Hynerpeton, Greererpeton, and Tulerpeton?

As for your request for ““almost-giraffe” fossils”, to Bohlinia I’d add Paleoryx, Canthumeryx, Sivatherium, Samotherium, Paleotragus, and Hunanotherium.

I’d suggest reading Donald Prothero’s Evolution - What The Fossils Say and Why It Matters, and you appear to be badly misinformed about the fossil record.


glsi - #64832

September 19th 2011

I guess you missed where I asked what were the immediate ancestor and successor was to Tiktaalik.    Which was the former and which was the later?


glsi - #64833

September 19th 2011

Sorry, I shouldn’t have asked that because I already know that no one has any idea whatsoever.  The longer your list of relatives gets, the vaguer and more speculative it appears.  Matheson warns above not to try to pin things down like this, I suppose because these things never work out and people end up looking foolish when they’re falsified.




John - #64835

September 19th 2011

“I guess you missed where I asked what were the immediate ancestor and successor was to Tiktaalik.”


I guess you missed the fact that we are discussing a metaphorical tree, not a metaphorical ladder.

So my question to you is, are you misrepresenting evolutionary theory intentionally?

Uncle Bonobo - #64840

September 19th 2011

“I guess you missed where I asked what were the immediate ancestor and successor was to Tiktaalik.    Which was the former and which was the later?”

br>
No, we haven’t found Tiktaalik’s parent and child.  I don’t expect we ever will.
br>
Just like finding the unmarked grave of a person who died in the Black Plague.  We probably won’t find their parents and children either.  But we know a parent existed.  We can make very good estimates as to what that parent probably looked like even though we don’t know the details.  
br>
Just like Tiktaalik’s parent.

glsi - #64834

September 19th 2011

By the way, I’m absolutely in stitches over the fact that two people  have now claimed I didn’t read Shubin’s book.  It certainly helps me understand how folks here are willing to make wild conclusions based upon a lack of evidence and false assumptions.


John - #64836

September 19th 2011

“By the way, I’m absolutely in stitches over the fact that two people  have now claimed I didn’t read Shubin’s book.”


gisi, how do you get from my expression of skepticism (“I’m skeptical that you ever read Shubin’s book, as he makes it very clear that we are talking about a metaphorical tree here.”) to falsely claiming that I flatly claimed that you didn’t read the book?

“It certainly helps me understand how folks here are willing to make wild conclusions based upon a lack of evidence and false assumptions.”

So if you’ve read the book, why do you keep insisting that there should be a ladder when we are discussing a tree?

And why do you continue to feign familiarity with the actual evidence when it’s clear that you are afraid to examine actual evidence?

Uncle Bonobo - #64841

September 19th 2011

John, ask him the age of the earth and you’ll get your answer.


All will then be clear.

John - #64851

September 20th 2011

It’s all clear now, UB. 


The question is, how clear is it to gisi? Clearly, at some level of consciousness s/he has no faith that s/he is right, because if s/he did, s/he wouldn’t be afraid of the evidence at all. 

beaglelady - #64855

September 20th 2011

If anyone wants to see a totally fascinating inside (literally) look at giraffes including their evolution and physiology, watch this:

http://www.youtube.com/watch?v=epwhHCNaMeE

They really are beautiful and amazing animals.

This video goes well with the original post here—what looks like giraffes’ knees are really their wrists; they actually have elongated hands!  And note the absurdity of the recurrent laryngeal nerve and its odd detour, making a nerve more than 15 feet long, down the neck and back up, to go from the brain to the larynx.  (If an appliance is a short distance from an electrical outlet, why use an absurdly long extension cord to plug it in?)   As they explain in the beginning of the video, a designer can go back to the drawing board and start from scratch, but evolution doesn’t have this luxury.


sfmatheson - #64859

September 20th 2011

Fascinating stuff! Those truly interested in giraffe evolution might look at the somewhat technical article linked below. Among other things, it explains why the stretch-to-reach-the-food hypothesis was never a very good explanation, although it continues to have some merit. (And yes, it was that explanation that Gould referred to as “fatuous”; see the link below to the relevant essay. Gould did not refer to giraffe phylogenies – then or now – as “fatuous,” and glsi’s superimposing of two different quotes from that essay is very misleading.) Interestingly, one currently favored hypothesis discussed in the technical article is that the longer neck resulted from sexual selection. The article mostly focuses on the paleontological data, and contrary to some reports in the comments above, makes these claims:


div>Throughout the giraffid fossil record there is clear evidence of progressive limb and neck elongation. Limb and neck elongation began with the prerequisite structural changes seen in the Leptomerycids, but it is in the palaeotragines that giraffe-like limb and neck elongation seems to gain momentum. Samotheres and Bohlinia continued the elongation at a faster rate.


Technical article: http://www.bringyou.to/GiraffeEvolution.pdf
Gould essay: http://books.google.com/books?id=qYbwHe4cl04C&lpg=PA309&ots=YXTUdfjbMs&dq=stephen jay gould giraffes fatuous&pg=PA318#v=onepage&q=fatuous&f=false

sfmatheson - #64860

September 20th 2011

And here’s a better link to the Gould essay at Google eBooks:

http://books.google.com/books?id=qYbwHe4cl04C&lpg=PP1&pg=PA318#v=onepage&q&f=false

glsi - #64861

September 20th 2011

And what of Gould’s:  ”...spotty evidence that gives no insight into how the long-necked modern species arose.”  Is that somehow out of context?  Is he somehow really saying the opposite of what his words say to me?  


My question was where are the fossils of the most recent ancestor to the modern giraffe?  Obviously, it is not even remotely close to Bohlinia.  For that many species to be missing from the flip-book strains credibility to say the least.

I am sure you are not ignorant of this.  By ignoring the evidence you give legitimacy to the claim that evolutionists only teach what they feel will support their theory while concealing the problems and contradictions.

sfmatheson - #64863

September 20th 2011

My own view is that using the word “contradiction” to refer to “not having the exact fossil at the exact time specified by the skeptical commenter” is deeply misleading.


I respect your skepticism and your choice to embrace different modes of explanation. I’m struggling to understand your consistently dismissive portrayals of professional scientists and your preference for a single sentence from a 1996 essay over an entire technical monograph which plainly expresses the opposite of your assertion. I find your characterizations of people here and of the scientists whose work we discuss to be unreasonably uncharitable, and your constantly shifting targets of derision do not reflect well on your commentary.

I hope you enjoy the rest of the series, and I hope you read a little bit more of the science that you seem to find so ridiculous. It should go without saying that I’ve reached a different conclusion.

glsi - #64908

September 22nd 2011

I really don’t know what shifting targets you’re talking about.  I have only one here and that’s the failure of the existing fossil record to adequately demonstrate the idea of Darwinian evolution.   That’s exactly what Gould is saying in that single sentence in regards to the modern giraffe.  It’s the core of what I’m saying, it’s true, and it’s perfectly appropriate that I would use it.


Of course, I don’t agree with Gould that the record he’s talking about is “spotty”.   Countless missing fossil species which might demonstrate a Darwinian evolution of the giraffe neck is a yawning chasm, not spotty.   And this is the problem of Darwinian evolution in general.  The fossil record does not reveal the slow, gradual change that is needed to validate the theory.   The “vast piles” of fossils which Darwin said would be necessary have never been found.  Vast piles have indeed been found, but they do not believably show one species morphing into some other species.

I apologize to you in particular, Dr. Matheson, for anything uncharitable.  Good luck in your work and I’ll look forward to the series.



 

beaglelady - #64914

September 22nd 2011

glsi,

Did you watch the video or read any of the articles?


John - #64918

September 22nd 2011

“I really don’t know what shifting targets you’re talking about.”


Sure you do.

“I have only one here and that’s the failure of the existing fossil record to adequately demonstrate the idea of Darwinian evolution.   That’s exactly what Gould is saying in that single sentence in regards to the modern giraffe.”

You’re simply lying now. If you actually believed that the antecedent of “the standard story” in your dishonest quote mine was the entire idea of Darwinian evolution, you would have answered the questions put to you.

“It’s the core of what I’m saying, it’s true, and it’s perfectly appropriate that I would use it.”

No, your means are completely dishonest even if you believed in your conclusion. Your fear of examining the evidence for yourself screams that you don’t.

How can you defend a religion that clearly teaches that the ends do not justify the means this way?

John - #64883

September 21st 2011

“Is that somehow out of context?”


In just about every way, but you already knew that. That’s why you quote mine and pretend to be familiar with the evidence—you have no faith that the evidence will support your position.

“Is he somehow really saying the opposite of what his words say to me?”

Why count on words from a dead man over evidence?

What’s the antecedent of “the standard story”? 

How many new girrafid fossils have been discovered since Gould wrote that? You’re afraid to look!
br>
“My question was where are the fossils of the most recent ancestor to the modern giraffe?”
br>
Where are the fossils of the passenger pigeon?
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“Obviously, it is not even remotely close to Bohlinia.  For that many species to be missing from the flip-book strains credibility to say the least.”
br>
Why?
br>
“I am sure you are not ignorant of this.  By ignoring the evidence…”
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Gisi, you are projecting. You are completely ignorant of the evidence and you intend to remain ignorant.
br>
”... you give legitimacy to the claim that evolutionists only teach what they feel will support their theory while concealing the problems and contradictions.”
br>
You haven’t presented a single contradiction.
br>
And this isn’t about teaching at all, but I can see why you would try to deceive your reader into believing that.

Ashe - #64864

September 20th 2011

i>Interestingly, one currently favored hypothesis discussed in the technical article is that the longer neck resulted from sexual selection.

i>
Fascinating

beaglelady - #64885

September 21st 2011

That’s true—in the giraffe video,  there is a clip of males bashing the hell out of each other by swinging their massive necks.  It’s quite shocking since giraffes have such sweet faces.

http://www.youtube.com/watch?v=epwhHCNaMeE


beaglelady - #64909

September 22nd 2011

Also, the long necks (and the patches) help the animals dissipate heat. Giraffes are able to browse in the heat of the day, when most animals have to rest in the shade.


modsynth - #65544

October 16th 2011

Remember, every gap filled by one transitional fossil makes two new gaps - one in front of it and behind it.  You can’t win.  If somehow circumstance would provide a seamless, flip-book style sequence of changes, you still wouldn’t be able to convince some people that one transitioned into the other.  “Were you there?” Ham would ask.  Hovind says they’re just dead things, we don’t know if they even had any offspring.  If someone is determined to deny common descent, than laying a few more data points on top of the mountain of evidence won’t make a difference.


Niall Bennington - #71529

July 31st 2012

Creationists (we all are essentially creationists, but you know what I mean) have carefully constructed an impenetrable coat of unfalsifiability around their Young-Earth-Creation “science”. 

Some attempt to discredit transitional fossils by saying that we don’t have every single piece of that fossil, we can’t know for sure that it’s transitional.  I was once in possession of a Creationist book series that claimed scientists could not know whether Ambulocetus (or Rodhocetus) was transitional because they didn’t have the legs.  They completely ignored all other feature of this transition that made it a genuine transition.

Many creationists faultily assume that when scientists say whales were descended from a hyena-like or hippo-like ancestor, they actually mean whales are descended from hippos or hyenas.  They then point out that since there are no hippos or hyenas in the fossil record before animals like Ambulocetus or Rodhocetus, “there is even less evidence for evolution.”

They usually insist that scientists believe proto-tetrapods like Tiktaalik suddenly “decided” it wanted to walk on land, and thus grew legs.  However, they usually do not understand the very process of tetrapod evolution. 

A perfect example of YEC unfalsifiability is the responses they throw out whenever a feathered dinosaur fossil is found:

1. It’s “just a bird”
2. Alan Feduccia doesn’t think it’s a dinosaur
3. The feathers are rare fossilization artifacts
4. The feathers are just long scales
5. The fossil came from China, so it’s probably a fake.

As a “backup” argument in case their arguments are shattered, they usually say something like “what’s stopping God from creating a dinosaur with feathers?”

Same with hominid fossils.  It’s got to be either “fully ape” or “fully human”.  Some Creation Organizations can’t reach a consensus on whether a certain fossil was human or ape.  The only way Creationists can address these transitional fossils that they demanded so adamantly is to change their definition of what qualifies as a transition.

I’m not trying to look down on anybody. I am only trying to show how, when digging down deep enough to look at the science, Young-Earth-Creationism fails scientifically in so many ways.  It’s mostly based on not really understanding what science has to say.  While YECs claim that both they and the scientists look at the same data but interpret it differently, I beg to differ.  I’m sure many here would agree.


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