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Author | Topic: All species are transitional | |||||||||||||||||||||||
JustinC Member (Idle past 4843 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
It would destroy every model of human evolution to date. Even so, the time frame is still short evolutionary speaking, so I don't think it would be that devestating to the evolutionary paradigm as a whole.
Now, if humans were found in fossils dating before the Triassic I think that would be devestating. This message has been edited by JustinC, 10-06-2005 11:37 AM
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
It would certainly make everyone stop and start looking for more observations. It would not destroy the concept of evolution through filtered mutations, but it would certainly show that there was still a major gap in the extent of our knowledge.
Now if, on the otherhand, we found clear evidence of modern mammals existing, say, 300 million years ago, then everyone would be back to the drawing board. Aslan is not a Tame Lion
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ausar_maat Member (Idle past 5498 days) Posts: 136 From: Toronto Joined: |
quote: the current one or the hypothesis?
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jar Member (Idle past 393 days) Posts: 34026 From: Texas!! Joined: |
I don't understand what you're asking.
Is that a quote from something I said? If so, I need to know where it originated so I can see the context. What do you mean by "the current one or the hypothesis?" Aslan is not a Tame Lion
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ausar_maat Member (Idle past 5498 days) Posts: 136 From: Toronto Joined: |
actually I was quoting JustinC,
I wondered what he meant
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JustinC Member (Idle past 4843 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
I meant that it really wouldn't be pushing the date back that far, in terms of the evolutionary time scale. You'd push it from about 200,000 years ago to 4 million years ago. There were mammals, more specificaly primates, 4mya so it could just indicate we evolved from a different lineage of which we have no knowledge.
If you push it back 300 mya, as jar said, we'd be in trouble in terms of our view of common descent. The reason being is that there weren't any official "mammals" back then, and therefore no primates. This wouldn't make sense in terms of common descent since we are most related to primates and should therefore have a relatively synchronous origin in the record (by synchronous I mean within the range of 30-50mya or so). It would really hurt the common descent paradigm if organisms just showed up randomly in the fossil record, i.e., humans 300mya, chimps 2.5mya, lizards 200,000 ya, etc.
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Chiroptera Inactive Member |
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:
Or, if we are using "species" as a valid classification then a species that goes extinct, without some of it's populations evolving into another species, is not transitional. 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 always considered a transitional to be a direct link between two species. 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:
Also, i've had this discussion with my Evo professor so I know I'm in the "wrong" compared to the scientific consensus. So it seems that the conversation is over. I don't really understand why it is continuing, except;
When a layperson hears that there is a transitional between two species, they think there is an evolutionary link. 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 "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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ausar_maat Member (Idle past 5498 days) Posts: 136 From: Toronto Joined: |
I'm in no position to make any affirmation, but I still wondered, since it seems the term "transitionals" is arbitrary and besides, all fossils from the tchadensis to the habilis were mainly found in Eastern Africa, 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? I mean they still don't really know if the tchadensis was actually on our side or the chip's for example.
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Chiroptera Inactive Member |
quote: It might seem that way to someone not familiar to the term, but it is not arbitrary. -
quote: 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. "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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JustinC Member (Idle past 4843 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
[deleted]
This message has been edited by JustinC, 10-06-2005 05:00 PM
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JustinC Member (Idle past 4843 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
To wrap this up, I'll concede that my definition was too stringent (which I did a few posts back).
My only concern with your definition is that it didn't mention chronology, which I think is a very important factor when we call something a transitional. You're definition would seem to show that a platypus is a transitional in the cynodont-mammal transition, which would lead me to believe there is something wrong with your definition. I'll also concede that my original statement "if a species goes extinct without another species budding off it, then it is not transitional" is wrong. The reason being is that this species can be very closely related to an animal that is a "missing link" in an ancestor-descendent relationship. So even though it is not the missing link, it could be considered transitional in that it shows intermediate morphology and existed in the correct time period. Transitional is intimately linked to the idea of missing links and really can't be defined otherwise. Any objections to the above? This message has been edited by JustinC, 10-06-2005 05:10 PM
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Chiroptera Inactive Member |
quote: 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. "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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Parasomnium Member Posts: 2224 Joined: |
Any objections to the above?
No objections. Now that that's out of the way, could we agree on a notion of 'transitional' that addresses the creationist argument of the missing transitionals? I think the problem they have with speciation is the reason they always talk about missing transitionals. The purpose of the argument in my opening post is that if it can be shown that transition is a very gradual, locally almost imperceptible process, then perhaps speciation is a bit less of a problem. This message has been edited by Parasomnium, 06-Oct-2005 10:31 PM We are all atheists about most of the gods that humanity has ever believed in. Some of us just go one god further. - Richard Dawkins
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robinrohan Inactive Member |
First, the term 'species' is an arbitrary, man-made concept That's what I was thinking too, and in that case your analogy about big and little numbers explains the arbitrariness very clearly. However, a popular definition now is "gene pool isolation," which I dislike because that makes the explanation that there are no "kinds" more difficult. When a gene pool gets isolated is not, I would think, an arbitrary designation. "Isolation" seems pretty definite to me.
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Brad McFall Member (Idle past 5032 days) Posts: 3428 From: Ithaca,NY, USA Joined: |
Psst, P;
Are evc regarding your headed threaders supposed to "agree" gradually on this amazons'source How do you think it is gradually possible to think around a creationist that might happen to disagree with Hamilton but agrees H saw through G's "all men are created equal and seperate magesterially"? This message has been edited by Brad McFall, 10-06-2005 07:16 PM
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