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Author Topic:   On Transitional Species (SUMMATION MESSAGES ONLY)
AustinG
Member (Idle past 3275 days)
Posts: 36
Joined: 04-06-2009


Message 31 of 314 (505380)
04-10-2009 8:50 PM
Reply to: Message 30 by New Cat's Eye
04-10-2009 12:13 PM


The point here is, that any given organism exhibits transition. Creationists ask "where are the transitional formas". I propose it is logical to conclude that a manitee is transitional (As long as it doesn't become an evolutionary dead end).

I don't want debate about the semantics of the word "transitional". I would like hear from the creationist camp on their thoughts on this argument. Is it not logical to conclude that an ancestor to the manitee began to venture into the ocean for food and now we have a "transitional" organism that is more fully adapted to aquatic life? As long as the manitee doesn't dead end, selection pressures will select for more aquatic features.

Likewise, it is likely they the Golopagos Iguana is transitional to a later more aquatic reptile

The legless lizard can be seen as transitional to a snake like creature.

The Ostrich is transition from bird to terrestrial animal.

Pinguins are transitional to a more aquatic animal

Flying squirrels, flying lizards, flying snakes, sirens (salemander with only 2 front legs), Kangaroo mice, beavers, sea otters. These are just the living "transitional" forms.

What about Homo erectus? Anthropologists document that the cranial capacity (how big the brain can get) varies from early Homo erectus (smaller) to later populations (larger). This is an indication of transition within one species. In fact, because of the encephalization and anotomical changes in later Homo eructus, later specimens are almost indistinguishable from early Homo sapians. Some anthropoligists say they are erectus, some say sapien; If this is not evidence of transition. Someone please enlighten me.

Go look this stuff up; not on wikipedia though. Do some actual research and learn anthropology before you claim there are no "transitional" forms.

Notice that I'm not discrediting evidence for intelligent design; I'm giving my own evidence for natural selection/evolution. This is a stance that more folks should take.

Okay, that was a little bit of a ramble, but it felt good.

Comment, complaints, questions?


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Replies to this message:
 Message 32 by Straggler, posted 04-10-2009 8:59 PM AustinG has responded
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Straggler
Member
Posts: 10284
From: London England
Joined: 09-30-2006


Message 32 of 314 (505381)
04-10-2009 8:59 PM
Reply to: Message 31 by AustinG
04-10-2009 8:50 PM


Transitional
I think he problem with your argument is that you seem to be suggesting an end point which is being sort of predeterminedly aimed at.

Yes each species is transitional.

But each is also well adapted to it's current environment.

You seem to be suggesting that each species should be viewed as a half-way-house to some sort of superior end-result as yet unreached.

That is not really how the whole thing works........


This message is a reply to:
 Message 31 by AustinG, posted 04-10-2009 8:50 PM AustinG has responded

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AustinG
Member (Idle past 3275 days)
Posts: 36
Joined: 04-06-2009


Message 33 of 314 (505387)
04-10-2009 10:51 PM
Reply to: Message 32 by Straggler
04-10-2009 8:59 PM


Re: Transitional
quote:
I think he problem with your argument is that you seem to be suggesting an end point which is being sort of predeterminedly aimed at.

No I'm not suggesting that there is an end result, quit the opposite. I'm pointing out that life is never static. Its always on its way to something else; never does an organism cease to change, and never to populations cease to evolve. There is no aiming; I realize this. Evolution is more like water flowing down a mountain; it takes the easiest path to an endless bottom.


This message is a reply to:
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Replies to this message:
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pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 34 of 314 (505395)
04-11-2009 1:54 AM
Reply to: Message 30 by New Cat's Eye
04-10-2009 12:13 PM


Catholic Scientist writes:

But just looking at their form, the hippo, sea lion, and manatee all look like steps along the path from land mammal to sea mammal.


I completely agree. Just as Ambulocetus looked like a step along the path from land animal to sea mammal.

Could we count those as transitionals?

Only if we change the definition of the word as used by biologists and paleontologists. While all of the organisms that you mentioned are most certainly a transition from some ancient, ancestral lineage to some different kind of organism some eons in the future, for the purposes of evolutionary biology and paleontology, transitional species/genera/clades show a mixture of two other groups (and only two other groups):

One group is the precursor group, although it is exceedingly rare that any specific species or lineage can be identified as an ancestor. Thus Archaeopteryx has been identified as a maniraptoran coelurosaur, even though we are unable to identify any specific, less general ancestor. But Archaeopteryx also has derived traits that are not present in any ancestral lineage.

The second group is the group that shows the derived traits. In the case of Archaeopteryx that group is birds. But no one seriously suggests that Archy is ancestral to birds. There is no evidence that it is true and considerable evidence that it is not true. Archy was one of many, many feathered lineages that existed. Most have gone extinct. One became modern birds. Thus, Archy is a transitional species between two large groups of organisms, dinosaurs and birds. Somewhere in the lineage of dinosaurs is one lineage that lead to Archeopteryx. Somewhere in that lineage is an ancestor of both Archy and modern birds.

So the point isn't whether or not hippos, sea lions, or manatees are transitional. They are not. They may be in transition, but they have only primitive traits and derived traits; the primitive traits shared with older lineages, and the derived traits that are unique. To be considered a transitional, a fossil (I know of no non-fossil transitionals) must show a retention of primitive traits from older lineages, as well as derived traits that also appear in subsequent lineages.

By the way, even though I know you weren't trying to indicate any sort of relatedness in your examples, hippos are Artiodactylas, more closely related to whales than other living groups, seals and sea lions are carnivores, related to bears/dogs/cats, and manatees are related to dugongs, whose closest living relatives may be elephants.


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 Message 30 by New Cat's Eye, posted 04-10-2009 12:13 PM New Cat's Eye has not yet responded

Replies to this message:
 Message 37 by Percy, posted 04-11-2009 8:38 AM pandion has responded

  
pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 35 of 314 (505398)
04-11-2009 2:50 AM
Reply to: Message 31 by AustinG
04-10-2009 8:50 PM


AustinG writes:

The point here is, that any given organism exhibits transition. Creationists ask "where are the transitional formas". I propose it is logical to conclude that a manitee is transitional (As long as it doesn't become an evolutionary dead end).


But that is the point. A transitional fossil, while it may be an evolutionary dead end, i.e., extinct, is an example of an organism that demonstrates a mix of primitive traits, from a more primitive lineage, and derived traits that are apparent in subsequent lineages. If there are not subsequent lineages, then, by definition, an organism cannot be transitional. Unless, of course, you wish to redefine the meaning of the word from the standard usage in biology and paleontology.

I don't want debate about the semantics of the word "transitional".

Of course you don't. But on the other hand, you are using the word with a non-standard meaning when it comes to biology and paleontology. If you actually wish to discuss evolutionary biology, then you don't get to redefine the vocabulary used by evolutionary biologists and still claim to be discussing evolutionary biology.

I would like hear from the creationist camp on their thoughts on this argument. Is it not logical to conclude that an ancestor to the manitee began to venture into the ocean for food and now we have a "transitional" organism that is more fully adapted to aquatic life? As long as the manitee doesn't dead end, selection pressures will select for more aquatic features.

That's all well and good, except for your non-standard use of the term "transitional." In transition, OK. But transitional to what?

Likewise, it is likely they the Golopagos [sic] Iguana is transitional to a later more aquatic reptile

Name it. You can't? Then whether or not it is in transition is irrelevant to whether it is a "transitional." If it goes extinct, than how is it transitional? I'm going to skip all of your other examples of unusual animals that may (or may not) evolve into other animals. They are all examples of living organisms with primitive and derived traits that are not intermediate between major lineages. Please learn what biologists and paleontologists mean when they talk about transitionals.

What about Homo erectus?

What about it? Are you not aware that Homo erectus is not a living species? Don't you actually recognize that H. erectus is completely irrelevant to your previous discussion of transitionals?

[delete of irrelevant nonsense]

If this is not evidence of transition. Someone please enlighten me.

But of course it is. But H. erectus has primitive traits from a more ancient lineage as well as derived traits from subsequent lineages. There are not H. erectus alive today.

What do hippos and manatees have to do with H. erectus in the context of this discussion, since hippos and manatees are living species, while H. erectus is not?


This message is a reply to:
 Message 31 by AustinG, posted 04-10-2009 8:50 PM AustinG has not yet responded

  
pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 36 of 314 (505399)
04-11-2009 3:03 AM
Reply to: Message 33 by AustinG
04-10-2009 10:51 PM


Re: Transitional
AustinG writes:

No I'm not suggesting that there is an end result, quit the opposite.


I do understand that.

I'm pointing out that life is never static. Its always on its way to something else; never does an organism cease to change, and never to populations cease to evolve.

Actually, sometimes it seems to be for quite long periods of time. It is called "stasis." The fact that adapted populations in stable environments do not tend to change for extended periods of time has been well known for more than 30 years.

There is no aiming;

Hopefully that is true.

Evolution is more like water flowing down a mountain; it takes the easiest path to an endless bottom.

That isn't even close to what I understand as the process of evolution through random mutation and natural selection, along with several other mechanisms of evolution. You're going to have to explain before that makes sense.
This message is a reply to:
 Message 33 by AustinG, posted 04-10-2009 10:51 PM AustinG has not yet responded

  
Percy
Member
Posts: 18369
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.9


Message 37 of 314 (505408)
04-11-2009 8:38 AM
Reply to: Message 34 by pandion
04-11-2009 1:54 AM


pandion writes:

To be considered a transitional, a fossil (I know of no non-fossil transitionals) must show a retention of primitive traits from older lineages, as well as derived traits that also appear in subsequent lineages.

There are two senses in which one might use the term transitional. One is the way you've just defined it, but this perspective is a mere artifact of the rate of morphological change of species (i.e., how long the species remained unchanged morphologically), and the fossils that have happened to be preserved and that we have chanced to find. This is a very useful perspective, and by way of example it is the one used to hypothesize the existence of Tiktaalik that was famously found by Neil Shubin.

The other sense of the term transitional is more accurate as it recognizes that our fossil window onto the past gives a false impression by providing the appearance of fixed species that do not change until suddenly evolution produces a new species. It understands that all species populations undergo change across all time, whether or not the change is fast or slow, and whether or not they are the type of changes that show up in the fossil record.

--Percy

Edited by Percy, : Improve wording in last para.


This message is a reply to:
 Message 34 by pandion, posted 04-11-2009 1:54 AM pandion has responded

Replies to this message:
 Message 38 by pandion, posted 04-12-2009 12:16 AM Percy has responded

    
pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 38 of 314 (505460)
04-12-2009 12:16 AM
Reply to: Message 37 by Percy
04-11-2009 8:38 AM


Percy writes:

There are two senses in which one might use the term transitional. One is the way you've just defined it, but this perspective is a mere artifact of the rate of morphological change of species (i.e., how long the species remained unchanged morphologically), and the fossils that have happened to be preserved and that we have chanced to find. This is a very useful perspective, and by way of example it is the one used to hypothesize the existence of Tiktaalik that was famously found by Neil Shubin.


Indeed true. And it is the one that is used by biologists and paleontologists.

The other sense of the term transitional is more accurate as it recognizes that our fossil window onto the past gives a false impression by providing the appearance of fixed species that do not change until suddenly evolution produces a new species. It understands that all species populations undergo change across all time, whether or not the change is fast or slow, and whether or not they are the type of changes that show up in the fossil record.

Actually, biologists and paleontologists are quite aware that fossils are only small peeks into the past. It doesn't mean that the term needs to be redefined. Believe it or not, biologists and paleontologists recognize that populations undergo change across time. In fact, biologists and paleontologists are aware that not only do populations change across time, they also know that they radiate. That is why there is rarely enough evidence to state definitively that any fossil species is descended from another fossil species. Evolution isn't a ladder with one species following another in a constant progression. Evolution is a bush, with constant radiation of populations. We can see this process happening today. Consider the 14 species of Darwin's finches, all descended from a common founding population about 2.3 mya. The closest relative in South America is a grassquit, specifically, Tiaris obscura. Molecular studies have shown that this is true. T. obscura diverged from other living Tiaris species before the Galapagos Islands were settled by these birds. Even today, the hybridization of three closely related species of Darwin's Finches has been noted. (Read "The Beak Of The Finch" by Jonathan Weiner. It won a Pulitzer Prize.

So, through that fossil window we find can observe a genus such as Archaeopteryx. We can't point to an ancestor even though it is obviously a maniraptoran coelurosaur. And we can't point to any descendant, even though it is obviously a bird. Given the scarcity of the fossil record, and given that beneficial traits tend to propagate through diverging populations, the best that we can hope for is a peek through a window into the past at a related species, one that shared an ancestor with the lineage of interest, and lived at the right time, and had the expected mix of traits. These are transitionals with no implication of fixed species waiting for evolution to change them. Your second sense of the term is one held by those who don't understand what is being discussed.


This message is a reply to:
 Message 37 by Percy, posted 04-11-2009 8:38 AM Percy has responded

Replies to this message:
 Message 39 by Percy, posted 04-12-2009 6:49 AM pandion has responded

  
Percy
Member
Posts: 18369
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.9


Message 39 of 314 (505471)
04-12-2009 6:49 AM
Reply to: Message 38 by pandion
04-12-2009 12:16 AM


pandion writes:

Indeed true. And it is the one that is used by biologists and paleontologists.

I think there may be a bit of minor confusion involved here. Biologists and paleontologists use both senses of the word "transitional". As with most word usage, which one they intend is usually clear from context.

What you're talking about is "transitional fossils," but you're claiming that the word "transitional" has only one definition as a short way of referring to "transitional fossil." That would be incorrect. The word "transitional" can refer to species in transition, and it can refer to a transitional fossil. Context usually reveals the intended meaning.

If you read the opening two paragraphs of the Wikipedia article on Transitional Fossils you'll see it makes the distinction fairly clear.

This thread is not about transitional fossils. It's about transitional species. The opening post, Message 1, briefly touches on the common confusion of transitional fossils with transitional species.

--Percy


This message is a reply to:
 Message 38 by pandion, posted 04-12-2009 12:16 AM pandion has responded

Replies to this message:
 Message 40 by pandion, posted 04-13-2009 1:19 AM Percy has responded

    
pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 40 of 314 (505509)
04-13-2009 1:19 AM
Reply to: Message 39 by Percy
04-12-2009 6:49 AM


Percy writes:

I think there may be a bit of minor confusion involved here. Biologists and paleontologists use both senses of the word "transitional". As with most word usage, which one they intend is usually clear from context.


Actually, your second use of the term is pretty much an unwillingness to actually define the term. It seems to be more philosophical gobblygook than anything meaningful. The first use would be pretty much clear from context. The second, with its windows onto [sic] the past and appearance of fixed species followed by the sudden onset of evolution to produce new species is drivel.

What you're talking about is "transitional fossils," but you're claiming that the word "transitional" has only one definition as a short way of referring to "transitional fossil."

So what excuse do you have for not reading what I said. I did not claim that I was offering the only definition of the word. What I said was the in the fields of evolutionary biology and paleontology the term has meaning in reference to a fossil species that shows traits from a more primitive lineage and derived lineages. You may use the word with any other definition that you wish in any context that you wish. But when you do so, you are no longer discussing evolutionary biology.

That would be incorrect. The word "transitional" can refer to species in transition, and it can refer to a transitional fossil. Context usually reveals the intended meaning.

Actually, I am correct. In the context of evolutionary biology and paleontology the word means what I said. I have no problem with calling such species as seals transitional. But it is a different definition of the word. Since seals are not intermediate between two lineages, they are not transitional in the sense used by evolutionary biologists.

I'm saying that you can use the word in whatever context and with whatever meaning you may wish. Please don't pretend that you mean the same thing as evolutionary biologists do when they use the term. Transitional species are extinct. Transitional clades may not be.

If you read the opening two paragraphs of the Wikipedia article on Transitional Fossils you'll see it makes the distinction fairly clear.

For the love of god! Wikipedia offered as a definitive source! I have actually contributed to and corrected Wikipedia on a number of topics. Sadly, what Wikipedia says and what you understand are two different things. You actually link to the page on "Transitional fossils" and chastise me for not understanding. I wonder if you actually read your own link. If you did, it is clear that you didn't understand what you read.

This thread is not about transitional fossils. It's about transitional species. The opening post, Message 1, briefly touches on the common confusion of transitional fossils with transitional species.

Then I wonder why you linked the Wikipedia page about transitional fossils. What did you have in mind? Of course, since no living species has primitive traits from an earlier lineage and derived traits that are evident in subsequent lineages, no living species is transitional. They may or may not be in transition. But we don't know that. Show me a transitional species and my question is, "transitional to what?"

As for the alleged confusion between transitional fossils and transitional species, I wonder who is confused. Even you attempted to explain the difference by linking a page on transitional fossils the didn't even discuss transitional species.


This message is a reply to:
 Message 39 by Percy, posted 04-12-2009 6:49 AM Percy has responded

Replies to this message:
 Message 41 by Percy, posted 04-13-2009 9:06 AM pandion has responded
 Message 44 by caffeine, posted 04-15-2009 7:57 AM pandion has responded

  
Percy
Member
Posts: 18369
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.9


Message 41 of 314 (505538)
04-13-2009 9:06 AM
Reply to: Message 40 by pandion
04-13-2009 1:19 AM


pandion writes:

Actually, your second use of the term is pretty much an unwillingness to actually define the term. It seems to be more philosophical gobblygook than anything meaningful. The first use would be pretty much clear from context. The second, with its windows onto [sic] the past and appearance of fixed species followed by the sudden onset of evolution to produce new species is drivel.

This garbled interpretation of what I said comes from my Message 37. Read it again. What you're calling my "second" definition of transitional is actually part of my characterization of the first definition, which is your definition, namely that "transitional" can only refer to a "transitional fossil." It is transitional fossils that I was describing as a window into the past that gives a misleading picture of suddenly emerging new species.

I define the two different senses of the word "transitional" in my Message 39 pretty clearly. The word "transitional" can refer to a transitional fossil. It can also refer more broadly to the fact that species are not static but are always in a state of change, a state of transition from what they are to something slightly different.

I did not claim that I was offering the only definition of the word. What I said was the in the fields of evolutionary biology and paleontology the term has meaning in reference to a fossil species that shows traits from a more primitive lineage and derived lineages. You may use the word with any other definition that you wish in any context that you wish. But when you do so, you are no longer discussing evolutionary biology.

It sounds like you're claiming that you're using the only valid definition of the term in the context of evolutionary biology, and that's not true. The idea that all species are transitional is a key concept within evolutionary biology.

For the love of god! Wikipedia offered as a definitive source! I have actually contributed to and corrected Wikipedia on a number of topics.

That's scary given the number of incorrect admonishments you keep issuing here.

Sadly, what Wikipedia says and what you understand are two different things. You actually link to the page on "Transitional fossils" and chastise me for not understanding. I wonder if you actually read your own link. If you did, it is clear that you didn't understand what you read.

Since I actually typed in "Wikipedia Article on Transitional Fossils" as the text for my URL, obviously I knew what article I was linking to. I suggested looking at the first two paragraphs, and I was hoping you would see this lead sentence in the second paragraph:

Wikipedia article on Transitional Fossils writes:

According to modern evolutionary theory, all populations of organisms are in transition.

I was just trying to provide you another place that mentions the concept of transitional species.

Then I wonder why you linked the Wikipedia page about transitional fossils. What did you have in mind?

Hopefully now you understand, but next time it might help to think a bit before putting fingers in gear. You're demonstrating the typical hothead's ability to jump to wrong conclusions.

Even you attempted to explain the difference by linking a page on transitional fossils the didn't even discuss transitional species.

Not discuss, but it *did* clearly describe populations as being in transition. Obviously the only one not reading things through is you.

It occurs to me that the intended meaning of transitional can be very clear even given very, very little context. Probably the term "a transitional" would almost always be used to refer to a transitional fossil.

--Percy

Edited by Percy, : Grammar.


This message is a reply to:
 Message 40 by pandion, posted 04-13-2009 1:19 AM pandion has responded

Replies to this message:
 Message 42 by pandion, posted 04-13-2009 11:27 PM Percy has responded

    
pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 42 of 314 (505607)
04-13-2009 11:27 PM
Reply to: Message 41 by Percy
04-13-2009 9:06 AM


Percy writes:

It occurs to me that the intended meaning of transitional can be very clear even given very, very little context. Probably the term "a transitional" would almost always be used to refer to a transitional fossil.

That's what I have been saying. Finally, I seem to have gotten through. But you did find it necessary to act like a child and try to insult me anyway. It is especially childish when in response to a question as to your intent.


This message is a reply to:
 Message 41 by Percy, posted 04-13-2009 9:06 AM Percy has responded

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Percy
Member
Posts: 18369
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.9


Message 43 of 314 (505619)
04-14-2009 8:14 AM
Reply to: Message 42 by pandion
04-13-2009 11:27 PM


pandion writes:

Percy writes:

It occurs to me that the intended meaning of transitional can be very clear even given very, very little context. Probably the term "a transitional" would almost always be used to refer to a transitional fossil.


That's what I have been saying

Actually, that's not what you were saying. You were saying that biologists and paleontologists only use the word transitional to refer to transitional fossils, and that the other sense of the word transitional was not part of their technical vocabulary. That is incorrect. That all populations everywhere are always in evolutionary transition is a central concept of evolutionary theory.

--Percy


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caffeine
Member
Posts: 1624
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.5


Message 44 of 314 (505677)
04-15-2009 7:57 AM
Reply to: Message 40 by pandion
04-13-2009 1:19 AM


Of course, since no living species has primitive traits from an earlier lineage and derived traits that are evident in subsequent lineages, no living species is transitional.

I'm not sure what you mean here; many living species share a mix of primitive and derived characteristics linking two clades. Monotremes share many primitve traits with reptiles, such as egg-laying and certain reptillian skeletal features; while sharing derived traits with other mammals such as fur and milk production.

I know you said that a living clade could be transitional but not a species, but the distinction seems unclear to me. A clade would be transitional because its members show a mixture of primitive and derived characteristics linking two groups; so why are the individual species showing this mixture not transitional? I don't see how the platypus differs so much from Archaeopteryx, which is not ancestral to modern birds and has derived traits not present in birds.


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pandion
Member (Idle past 1107 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 45 of 314 (506006)
04-21-2009 2:16 PM
Reply to: Message 44 by caffeine
04-15-2009 7:57 AM


caffeine writes:

I'm not sure what you mean here; many living species share a mix of primitive and derived characteristics linking two clades. Monotremes share many primitve traits with reptiles, such as egg-laying and certain reptillian skeletal features; while sharing derived traits with other mammals such as fur and milk production.


Right. I guess the Order Monotremata could be considered transitional. However, I would be more likely to think of some of the early fossil families of Monotremes (11 species, 7 genera, 4 families) as transitional. They would certainly be transitional between a primitive, mammal like reptile and the modern Monotremes (5 species, 3 genera, 2 families). Are you sure that Monotremes don't have any unique derived traits (i.e., traits that do not exist in either reptiles or other lineages of mammal)?

I know you said that a living clade could be transitional but not a species, but the distinction seems unclear to me.

It is? How can that be when you have given an example in discussing Monotremes? You were aware that Montremata is a taxonomic Order, weren't you?

A clade would be transitional because its members show a mixture of primitive and derived characteristics linking two groups; so why are the individual species showing this mixture not transitional?

Because they represent only one of several species that fit the description. The entire lineage is transitional.

I don't see how the platypus differs so much from Archaeopteryx, which is not ancestral to modern birds and has derived traits not present in birds.

Really? What derived traits in Archaeopteryx are not present in birds? My investigations have been about only those traits which are reptilian or avian. To be honest, I'm not even aware of any that are neither.

But at least you didn't use Wikipedia and completely misunderstand what even that less than stellar source says. Just because all populations can be considered to be "in transition" does not mean that they are transitional forms. Even Wikipedia makes it clear that a transitional is a form that represents the point at which lineages diverge.

Just as an exercise I thought I would dig up some argument from authority. For example, noted evolutionary geneticist Jerry A. Coyne says in his book Why Evolution Is True that evolutionary theory predicts that:

We should be able to find examples of species that link together major groups suspected to have common ancestry, like birds with reptiles and fish with amphibians. Moreover, these "missing links" (more aptly called "transitional forms") should occur in layers of rock that date to the time when the groups are supposed to have diverged. - p18

Moreover, in 25 index entries under "transitional forms", not one discusses a living species that is not an intermediate between two groups.

Zoologist Tim Berra says in his book, Evolution And The Myth Of Creationism, under the section heading "Transitional Fossils", says:

These examples(and there are many others) demonstrate that fossils intermediate between major groups do exist, as predicted by evolution.

My emphasis.

In 10 other discussions of transitional fossils in the book, all are discussions of fossils that are intermediate between two major groups of organisms.

Pat Shipman, a paleoanthropologist who became interested in the Archaeopteryx because of Fred Hoyle's embarrassing effort to discredit the London specimen. Shipman mentions that a traditional argument against The Origin of Species was that if over time there has been a gradual evolutionary change of one type of organism into another, where are the transitional forms? It is clear that, to Shipman, a transitional form is a form between two other groups. Shipman even points out that Darwin mentioned in the chapter "Difficulties of the Theory" the "absence or rarity of transitional varieties" in the fossil record. So it seems that even Darwin meant an intermediate between two other forms when he used the word.

Finally, there is Donald Prothero, a respected paleontologist. In his book Evolution: What the Fossils Say and Why It Matters, discusses Gould's often misquoted statement about the frequency of transitional forms. As Gould later explained, he actually meant that transitional forms between species are rare while there are many between larger groups.

Finally, there is the web site from the University of California Museum of Paleontology. A page from that site is entitled Transitional Forms On that page it states:

Fossils or organisms that show the intermediate states between an ancestral form and that of its descendants are referred to as transitional forms.

I know of nowhere on that rather extensive site where the term "transitional" is used in reference to a living species that has not diverged.

But, if you want to call seals and manatees transitional, feel free. But please be aware and make it clear when you do so that you are using a word with a non-standard definition outside the field of evolutionary biology.


This message is a reply to:
 Message 44 by caffeine, posted 04-15-2009 7:57 AM caffeine has not yet responded

Replies to this message:
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