All species are transitional

Maybe. But if the platypus went extinct, wouldn't it still be considered a transitional between placental mammals and non-mammal therapsids? Transitional isn't a direct link between a ancestor and descendent species -- a transitional is a species that retains many primitive features of the common ancestor as well as derived features that are found in related lineages that have lost the primitive features.Edited to add the last six words.This message has been edited by Chiroptera, 04-Oct-2005 05:39 PM

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I always considered a transitional to be a direct link between two species.

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Scientists consider archeaopteryx to be a transitional species between modern birds and theropod dinosaurs. No scientist considers archaeopteryx to be an ancestral species to modern birds. Is this consistent with your concept of "transitional"?

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Transition means to change from one form to another.

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Yes, in everyday English that is exactly what "transition" means. And since archaeopteryx helps us in understanding the transition from theropod dinosaur to modern bird, the label "transitional fossil" is quite appropriate.Now I have another question. No fossil species are known to be in a direct ancestor/descendent link to any other species. Therefore, according to your definition, there are no transitionals known. Therefore, we have no examples of transitionals. So the word transitional is a word that applies to nothing. Does this square with your understanding?

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"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

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There is much utility in defining transitionals the way you do.

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Which is why scientists use that definition. Definitions in any scientific field are made so as to be useful. The goal of much of evolutionary biology is to determine the lineages of known species, and perhaps the causes and constraints of those evolutionary changes. The only species that scientists have to work with are the known species, either the extant species or those known in the fossil record. Species like archaeopteryx give a large amount of insight into the evolution of birds, so fossils like archaeopteryx are special. This quality of being special is termed "transitional". You might not like it, but that is the way it is. One could use "transitional" to mean a direct ancestor/descendent link, but since we cannot identify actual ancestors with any degree of confidence, this definition would not be very useful to a scientist.-

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In the end it's just semantics.

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The purpose of have precise definitions in science is to avoid semantics issues. When laypersons insist on making up words or using their own definitions, they are creating semantics issues that scientists would prefer to avoid.

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"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

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And isn't it disingenuous to tell them we have have transitionals when we are using a different definition than them?

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No, since almost everything I have read about "transitionals" written for the layperson explains what a transitional is.

I realized that my statement about transitionals (about the platypus being a transitional) was a bit broad. I realized usually there are some time frame considerations. I was ready to back down from my hyperbolic claim if I had been challenged on this point.But this was not the challenge you made. Your point (to which I was responding) was: Here, you are implying that a transitional is a species that is in a direct ancestor-descendent line. To show that I am not misreading this, you further state: I was pointing out that this is incorrect. If you have two taxa, one of which is descended from a species of the other taxa (although not necessarily from any known species in that taxa), a transitional species is a species that is closely related to the two taxa and has both primitive characteristics of the ancestral taxon that are not possessed by the descendent taxon as well as some of the derived characteristics of the descendent taxon.My platypus example fits very well into the spirit of this definition: the platypus has primitive characteristics no longer possessed by modern placental mammals (lays eggs, does not have nipples, has a cloaca) as well as derived characteristics of modern placental mammals (furry, produces milk, warm-blooded). Where the platypus fails to satisfy the definition is that it may not be close enough in relation to modern placental mammals or ancient non-mammal therapsids to qualify as a true transitional. If you object to the example of the platypus as a transitional based on this, then fine -- it was meant to be a bit of hyperbole to start a conversation, which it seemed to have done.I also note that you later admit: So it seems that the conversation is over. I don't really understand why it is continuing, except; You seem to be a bit offended that the scientific definition is different that what the public thinks the definition is. You give the impression that you feel that scientists should accept the common definition, although I'm not sure why you would think this. In fact, you seem to be implying that by using a scientific term correctly a scientist is (perhaps unintentionally) misleading the public.First, you claimed that a transitional was a direct link on the ancestor-descendent line.Then you seem to admit that this isn't the scientific definition of transitional, but insist that it should be.So, let me repeat my points, just to make sure that we are having the same conversation:There are no fossil species that can be definitely placed in a direct ancestral line to any other fossil or living species. The most that can be claimed for any fossil species is that, at best, it is closely related to an ancestral species, but it can never be claimed to be ancestral itself. (Well, one can make a claim, I suppose, but this would be a claim with no way of verification).Since these closely related species do give good information about the actual ancestral species as well as information about the details of the evolution of the lineage, these species are important to the study of evolution.These species are so important that it is convenient to give this type of species a name. The word "transitional" is used, because these species give good information concerning the transition between the common ancestor and the more modern species.I brought up the platypus since it exhibits a lot of the features that we expect from a "transitional species". It may not be considered an actual transitional species since it is not all that closely related either to the modern placental mammals, nor to the ancient cold-blooded, hairless therapsid ancestor, but I was willing to concede this if someone objected on these grounds. It was an example to illustrate that a transitional does not necessarily lie on a direct ancestral line to a modern species.Your objection, though, was not because the platypus failed to meet a specific technical criterion, but because you were using a completely wrong (in the scientific sense) definition of "transitional".Now I cannot tell if you are still trying to claim that your initial definition is the correct one, or you are now moving onto a different argument altogether.Edited to correct a typo.This message has been edited by Chiroptera, 06-Oct-2005 06:37 PM

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"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

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since it seems the term "transitionals" is arbitrary

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It might seem that way to someone not familiar to the term, but it is not arbitrary.-

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wouldn't the discovery of a more modern homo sapien in a much earlier period just indicate that, perhaps, the species we simply other species now extinct?

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I'm not sure what your question is, but I am not one to speculate on what the meaning of such a discovery would be.

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"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

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Any objections to the above?

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No objections.You are correct in that many people who hear "transitional" think it refers to a direct ancestor to a later species; creationists do capitalize on this when they "prove" that a widely accepted transitional cannot be an actual ancestor, and thus muddy the waters. Therefore it is important that if there is the possibility of misunderstanding to clarify what is meant by a "transitional".And I certainly don't mind if someone does use the word "transitional" to mean a direct ancestor of a modern species; however, since other people may think that the word means something else there is apt to be confusion, and so it become important to make sure everyone understand how the word is actually being used in the particular conversation, and it is important to be aware of this difference in meaning when quoting other people.I try to make sure that people understand what I mean when I use the word "transitional", either by directly stating my meaning or by making sure the context is clear, although I am sure that I have neglected this.At times I will also call Homo erectus or Australopithecus afarensis human ancestors, or I will call Pakicetus a whale ancestor, or similar errors, even though we can never be sure that these creatures are really ancestors. But I hope that people will not take exception to this, seeing how the actual error is relatively small; nonetheless, people may accuse me of unnecessarily confusing the issues.

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"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt

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Untold hundreds upon hundreds of thousands species have come and gone and geologic formations failed to capture any of them transitioning ?

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Fortunately, we have lots of examples of species "transitioning" in the fossil record.(Copied from Douglas Theobald's article to ImageShack to save TalkOrigin's bandwidth.)This message has been edited by Chiroptera, 19-Oct-2005 10:51 PM

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"Intellectually, scientifically, even artistically, fundamentalism -- biblical literalism -- is a road to nowhere, because it insists on fidelity to revealed truths that are not true." -- Katha Pollitt