Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 77 (8905 total)
Current session began: 
Page Loaded: 04-22-2019 2:13 AM
18 online now:
PaulK (1 member, 17 visitors)
Chatting now:  Chat room empty
Newest Member: WookieeB
Post Volume:
Total: 850,006 Year: 5,043/19,786 Month: 1,165/873 Week: 61/460 Day: 3/58 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
1
23456
...
21NextFF
Author Topic:   On Transitional Species (SUMMATION MESSAGES ONLY)
AustinG
Member (Idle past 3276 days)
Posts: 36
Joined: 04-06-2009


Message 1 of 314 (505014)
04-06-2009 3:06 PM


Opponents to the theory of evolution often point out the lack of transitional fossils/organisms; I believe this is due to a misunderstanding of transitional species.

The theory of evolution argues that all life on earth is continually under change; it is never static. With this in mind, every organism can be seen as transitional. Some animals are more noticeably transitional than others. Alligators, for instance, live both on land and in water. Ostrichs are birds that can not fly and pinguins are birds that have adapted to swim. Are these not excellent examples of transitional organisms?

Please share your arguments for or against this idea and any other comments you may have; however, please stay on topic.

Edited by AustinG, : No reason given.

Edited by Adminnemooseus, : Add the "(Summation Messages Only" to topic title.


Replies to this message:
 Message 3 by pandion, posted 04-06-2009 4:27 PM AustinG has not yet responded
 Message 4 by kuresu, posted 04-06-2009 4:39 PM AustinG has responded
 Message 29 by Peter, posted 04-10-2009 11:54 AM AustinG has not yet responded

    
Admin
Director
Posts: 12589
From: EvC Forum
Joined: 06-14-2002
Member Rating: 3.4


Message 2 of 314 (505018)
04-06-2009 3:35 PM


Thread moved here from the Proposed New Topics forum.
    
pandion
Member (Idle past 1108 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 3 of 314 (505021)
04-06-2009 4:27 PM
Reply to: Message 1 by AustinG
04-06-2009 3:06 PM


While it is true that all organisms can be referred to as transitional because all populations of organisms are ever changing, in biology the term transitional is most often used when discussing fossil species. These fossils show a mixture of traits, some referred to as "primitive" that come from an ancestral lineage, and some referred to as "derived" that appear in all subsequent lineages. Since living organisms don't have subsequent lineages, they are not technically transitional forms.
This message is a reply to:
 Message 1 by AustinG, posted 04-06-2009 3:06 PM AustinG has not yet responded

Replies to this message:
 Message 13 by Taz, posted 04-07-2009 2:02 PM pandion has not yet responded
 Message 14 by Larni, posted 04-07-2009 2:09 PM pandion has responded

  
kuresu
Member (Idle past 620 days)
Posts: 2544
From: boulder, colorado
Joined: 03-24-2006


Message 4 of 314 (505022)
04-06-2009 4:39 PM
Reply to: Message 1 by AustinG
04-06-2009 3:06 PM


I think you might have transitional a little misunderstood or unclear. The transition your examples brings to mind is that of a transition to a new environment. Penguins have transitioned to water, ostriches to land, and alligators to both.

To be clear, a transitional species is B in the series A->B->C. It has nothing to do with their environment but with their placement in the genealogical family tree. In that sense, my mother (B) is the transitional from my maternal grandparents (A) to me (C).


This message is a reply to:
 Message 1 by AustinG, posted 04-06-2009 3:06 PM AustinG has responded

Replies to this message:
 Message 5 by Chiroptera, posted 04-06-2009 5:38 PM kuresu has not yet responded
 Message 6 by AustinG, posted 04-06-2009 8:57 PM kuresu has not yet responded
 Message 8 by pandion, posted 04-07-2009 12:55 AM kuresu has responded

    
Chiroptera
Member
Posts: 6531
From: Oklahoma
Joined: 09-28-2003


Message 5 of 314 (505027)
04-06-2009 5:38 PM
Reply to: Message 4 by kuresu
04-06-2009 4:39 PM


To be clear, a transitional species is B in the series A->B->C.

Actually, in paleontology, that isn't quite true. It would actually be a very rare event to find species B in any lineage -- and even if B were found, it would be difficult to determine whether it was really in direct line between A and C or on a side branch.

A transitional species is actually a species that is another descendent of B but close enough in time so that it retains many of B's characteristics that C has lost, and so can say something about what B must of looked like.

Consider the diagram:

                  A
                  |
      ------------B-----------
      |                        |
------C------                 D
|             |
E           F

Now E and F are modern species that help difine a taxon, like a modern mammal and a modern salamander are tetrapods. The had a common ancestor, C, and further back they had a more fish-like ancestor, B. B is unlikely ever to be found. However, B had other descendent species, like D which would represent, for example, Tiktaalik. Now D (and Tiktaalik) is not an ancestor to E and F; however, it is close to the ancestor B in time, and would still have many of the same physical characteristics. So D gives a lot of insight into what the Actual ancestor, B, was like.

Having found D and recognizing its significance, we would label D as a transitional fossil.

Edited by Chiroptera, : Oops. Hit submit instead of preview.


To count as an atheist, one needn't claim to have proof that there are no gods. One only needs to believe that the evidence on the god question is in a similar state to the evidence on the werewolf question. -- John McCarthy
This message is a reply to:
 Message 4 by kuresu, posted 04-06-2009 4:39 PM kuresu has not yet responded

  
AustinG
Member (Idle past 3276 days)
Posts: 36
Joined: 04-06-2009


Message 6 of 314 (505041)
04-06-2009 8:57 PM
Reply to: Message 4 by kuresu
04-06-2009 4:39 PM


Loose Definition
My use of transitional was a little loose for sure. Thanks for bringing to my attention that transitional has more to do with perspective.

Let me refrase. In the future pinguin fossils could be considered as a transitional form between bird and sea creature.


This message is a reply to:
 Message 4 by kuresu, posted 04-06-2009 4:39 PM kuresu has not yet responded

Replies to this message:
 Message 7 by CosmicChimp, posted 04-06-2009 10:17 PM AustinG has not yet responded

    
CosmicChimp
Member
Posts: 306
From: Muenchen Bayern Deutschland
Joined: 06-15-2007


Message 7 of 314 (505047)
04-06-2009 10:17 PM
Reply to: Message 6 by AustinG
04-06-2009 8:57 PM


penguins as transition?
As far as speculation goes, I think penguins are a dead end. They're too specialized, as far as I can tell, to survive the environmental changes that would otherwise make them into a full-time ocean animal. Here I'm assuming the land breeding locations they need to breed and rear chicks to be unavailable.

Amphibians or other non cetacean mammals (like seals) might be able to make it back to the water full time.

Edited by CosmicChimp, : changed heading


This message is a reply to:
 Message 6 by AustinG, posted 04-06-2009 8:57 PM AustinG has not yet responded

  
pandion
Member (Idle past 1108 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 8 of 314 (505052)
04-07-2009 12:55 AM
Reply to: Message 4 by kuresu
04-06-2009 4:39 PM


kuresu writes:

I think you might have transitional a little misunderstood or unclear. The transition your examples brings to mind is that of a transition to a new environment. Penguins have transitioned to water, ostriches to land, and alligators to both.


Indeed. Not what the term "transitional" generally means.

To be clear, a transitional species is B in the series A->B->C. It has nothing to do with their environment but with their placement in the genealogical family tree. In that sense, my mother (B) is the transitional from my maternal grandparents (A) to me (C).

But that's not what biologists/paleontologists mean either. A transitional species is not claimed to be descended from any specific species and is not claimed to be ancestral to any specific species. Take Archaeopteryx for example. It is obviously descended from a maniraptorian dinosaur. The specific ancestor is unknown. The maniraptorian dinosaur Compsognathus is distinguishable from Archaeopteryx because of the length of the arms. Archy also has traits that are characteristic of birds, flight feathers being the most salient, along with a opposable hallux (at least partially), furcula from fused clavicles, elongated and backward directed pubis, pneumatic bones, and so on. Archaeopteryx is a transitional species because it has primitive traits from a prior lineage (even though a specific ancestor cannot be identified), and because it has derived traits that are evident in subsequent lineages (even though no specific descendant can be identified). The point is that Archaeopteryx is found with traits that are intermediate between bird and dinosaur in geological deposits that are of the correct age. Archy may or may not be ancestral to modern birds. The point is that in Chiroptera's chart, Archy may be "D", an extinct species where "E" and "F" are modern birds. Evolution is not a ladder, where one species slowly evolves into another forever. Evolution is a bush, where one species becomes two or more over and over again. Most of those branches become extinct.

Edited by pandion, : Clarification


This message is a reply to:
 Message 4 by kuresu, posted 04-06-2009 4:39 PM kuresu has responded

Replies to this message:
 Message 9 by kuresu, posted 04-07-2009 11:00 AM pandion has responded

  
kuresu
Member (Idle past 620 days)
Posts: 2544
From: boulder, colorado
Joined: 03-24-2006


Message 9 of 314 (505089)
04-07-2009 11:00 AM
Reply to: Message 8 by pandion
04-07-2009 12:55 AM


I'm well aware of this.

I just thought it would be fair to say that archaeopteryx is (B), it's unkown descendant is (C), and its ancestor, a maniraptorian dinosaur, is (A).

Besides, if we do actually know the lineage (I'm thinking of the forams although I'm probably remembering that wrong, or human evolution where we almost certainly know that our ancestor is H. erectus, with the question remaining over whether H. erectus is descended from H. habilus or if the two are cousins), I would think that B could be called transitional.


This message is a reply to:
 Message 8 by pandion, posted 04-07-2009 12:55 AM pandion has responded

Replies to this message:
 Message 10 by CosmicChimp, posted 04-07-2009 11:20 AM kuresu has not yet responded
 Message 11 by pandion, posted 04-07-2009 12:22 PM kuresu has responded

    
CosmicChimp
Member
Posts: 306
From: Muenchen Bayern Deutschland
Joined: 06-15-2007


Message 10 of 314 (505091)
04-07-2009 11:20 AM
Reply to: Message 9 by kuresu
04-07-2009 11:00 AM


Hi Kuresu,

I don't see how you can be so sure as to put "Archy" into a "B" position without direct evidence. Read Chiroptera's post again he explains why Archy is best shown to be at D.


This message is a reply to:
 Message 9 by kuresu, posted 04-07-2009 11:00 AM kuresu has not yet responded

  
pandion
Member (Idle past 1108 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 11 of 314 (505100)
04-07-2009 12:22 PM
Reply to: Message 9 by kuresu
04-07-2009 11:00 AM


Could be. That's why I said that Archy "may" be "D". The point is that we can't say for certain. But Archy does have the right mix of traits and it lived at the right time. It is most probably an extinct branch from the lineage that led to birds.

But my main point was really your example of your grandparents, your mother, and you. You see, you are all the same species (I presume) and are not even an interbreeding population of that species. It's hard enough to explain that the term "transitional species" does not necessarily mean "descended from" nor does it mean "ancestral to". That's what creationists constantly claim and that's what your example implies. I believe that we must be careful not to give that impression when discussing transitional species.

Edited by pandion, : spelling correction.


This message is a reply to:
 Message 9 by kuresu, posted 04-07-2009 11:00 AM kuresu has responded

Replies to this message:
 Message 12 by kuresu, posted 04-07-2009 1:48 PM pandion has responded

  
kuresu
Member (Idle past 620 days)
Posts: 2544
From: boulder, colorado
Joined: 03-24-2006


Message 12 of 314 (505104)
04-07-2009 1:48 PM
Reply to: Message 11 by pandion
04-07-2009 12:22 PM


It's hard enough to explain that the term "transitional species" does not necessarily mean "descended from" nor does it mean "ancestral to".

Wait, what?

I thought that was basically the whole point of transitionals. That they show the potential evolutionary lineage.

You want to ask how a fish became a frog, that's where transitionals come in.

You want to ask how a frog become a reptile, that's where transitionals come in.

You want to ask how some cattle-like creature became a whale, that's where transitionals come in.

You want to ask how Hyracotherium became the modern horse, that's where transitionals come in.

Even if the example we have isn't B, it still shares an ancestor with B. If it doesn't have such an ancestral link, it's worthless as a transitional, no?

Chirop's Chart, D being the transitional example we've found:
A
|
------------B-----------
| |
------C------ D
| |
E F

Example D disconnected.
A G
| |
------------B- |
| |
------C------ D
| |
E F

If this is the case, it's no longer a transitional, right?

But my main point was really your example of your grandparents, your mother, and you. You see, you are all the same species (I presume) and are not even an interbreeding population of that species.

Obviously, it was an example to get the point across. I don't see what the problem with being a non-interbreeding population is, since a transitional species obviously doesn't interbreed with it's parent or daughter species. As to being the same species, I'm talking about a genealogical family tree for crying out loud. Did the allegory completely miss? Besides, the point was that you use the middle to show how the changes appeared from A to C, and one species or many can show that.
This message is a reply to:
 Message 11 by pandion, posted 04-07-2009 12:22 PM pandion has responded

Replies to this message:
 Message 16 by pandion, posted 04-07-2009 7:41 PM kuresu has responded

    
Taz
Member (Idle past 1399 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 13 of 314 (505107)
04-07-2009 2:02 PM
Reply to: Message 3 by pandion
04-06-2009 4:27 PM


pandion writes:

Since living organisms don't have subsequent lineages, they are not technically transitional forms.


Not true. Population A splits into populations A and B. B evolves into C. A and C coexist in the same time period. A is a transitional of whatever that came before A and C.
This message is a reply to:
 Message 3 by pandion, posted 04-06-2009 4:27 PM pandion has not yet responded

  
Larni
Member
Posts: 3976
From: Liverpool
Joined: 09-16-2005


Message 14 of 314 (505108)
04-07-2009 2:09 PM
Reply to: Message 3 by pandion
04-06-2009 4:27 PM


Welcome to EvC, Pandion.

Are you the Pandion from 4Forums.com?


This message is a reply to:
 Message 3 by pandion, posted 04-06-2009 4:27 PM pandion has responded

Replies to this message:
 Message 17 by pandion, posted 04-07-2009 7:43 PM Larni has not yet responded

    
Taq
Member
Posts: 7694
Joined: 03-06-2009
Member Rating: 4.5


Message 15 of 314 (505111)
04-07-2009 3:13 PM


"In looking for the gradations by which an organ in any species has been perfected, we ought to look exclusively to its lineal ancestors; but this is scarcely ever possible, and we are forced in each case to look to species of the same group, that is to the collateral descendants from the same original parent-form, in order to see what gradations are possible, and for the chance of some gradations having been transmitted from the earlier stages of descent, in an unaltered or little altered condition."--Origin of Species, Chapter 6

Since it is impossible to tell without DNA the exact relationship between fossils it is always assumed that they are collateral descendants (as described by Darwin) who have preserved characteristics found in the common ancestor. With this understanding, one can not draw a non-arbitrary line beyond which a species is too distantly related to the common ancestor in order to evidence a transition. For that reason, the duck billed platypus is as transitional between reptiles and placental mammals as H. erectus is transitional between modern humans and our common ancestor with chimps.


  
1
23456
...
21NextFF
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019