Freethought & Rationalism Archive

ps418 · 12-29-2001, 08:33 PM

This gives me an excuse to use another quote from the Phylum Level Evolution page:

There are a couple of cautions about the use of the term phyla. A phylum is assigned to a given creature based upon its having the shared characteristic body plan. Occasionally, however, different body plans are not assigned different phyla and this creates an appearance that phyla can't evolve. A case in point concerns a deep-sea sponge which is classed with the Porifera in spite of the fact that it has an entirely different body plan. Vacelet and Boury-Esnault (1995, p. 335) relate:

�Our results raise fundamental questions about the validity of characteristics used to distinguish the phyla of lower invertebrates. A sponge is defined as a �sedentary, filter-feeding metazoan which utilizes a single layer of flagellated cells (choanocytes) to pump a unidirectional water current through its body. Except for being sedentary, the cave Asbestopluma and presumably all Cladorhizidae lack these basic sponge attributes. In an extreme environment where active filter-feeding has a low yield, cladorhizids have developed a mode of life roughly similar to that of foraminiferans or cnidarians. Their feeding mechanism relies on passive capture of living prey and on transfer of nutrients into the body through intense cell migrations, the analogue of cytoplasmic streaming in foraminiferan pseudopodia. This may be compared to the emergence of macrophagy in abyssal tunicates, also accompanied by a reduction of the filtering system although in Cladorhizidae the result is more extreme, with a main body plan different from Porifera and resembling no other modern anatomical design.�
�Such a unique body plan would deserve recognition as a distinct phylum, if these animals were not so evidently close relatives of Porifera. Their siliceous spicules show clear similarities to several families of poecilosclerid Demospongiae.�

In cases like that above, the lack attribution of phylum rank for these 'sponges' hides the fact that the Porifera may very well have given rise to an independent phyla. The only real connection between the two groups are the spicules which act as evidence of common descent. If the Cladorhizid sponges were to lose the spicules, the connection between the two groups would be lost. Body plans are obviously more of a continuum and difficult to separate than the simplistic concept of phyla espoused by anti-evolutionists would imply.

Ref:

Vacelet, J. and N. Boury-Esnault, 1995. �Carnivorous Sponges,� Nature, 373:333-335.

MrDarwin · 12-30-2001, 05:48 AM

Quote:

From my perspective, you seem to entirely miss my point. If evolution is happening, we would be expecting ever greater and more diverse numbers and examples of phyla all of the time.

Why? Ask him why this should be so. Most of all, ask him where he thinks the new phyla would come from.

I made some comments specifically about this problem on <a href="http://www.arn.org/ubb/Forum1/HTML/001450.html" target="_blank">this thread</a> at ARN. In an nutshell, I don't believe new phyla appear for two reasons: (a) the living phyla are the descendants of the survivors of the earliest radiation of the metazoa, a unique event in the history of life, and (b) anything really new and different that appeared since then wouldn't be appearing from nowhere, but rather would have to evolve from a member of an existing phylum, and so would tend to be pigeonholed in that phylum by taxonomists.

Sacculina, a really creepy parasite, would get my vote as a candidate for a new phylum; the problem is, the larval stage clearly indicates its ancestry as an arthropod, and specifically as a highly specialized barnacle.

[ December 30, 2001: Message edited by: MrDarwin ]

Dr Rick · 12-30-2001, 10:16 AM

Quote:

Originally posted by ps418:
I'm feeling lazy right now...

Wow, Patrick; nice job.

Thanks,
Rick

tgamble · 01-01-2002, 06:18 PM

Well, I gave all that info to the creationist I was talling you about and got this in reply.

Quote:

Now, regarding the Cambrian Explosion, I can tell you that Dr. Paul Chien is chairman and professor of biology at the University of San Francisco. He is not only a renowned zoologist with published papers in more than 50 journals, but also has several international lecture tours to his credit.

He is a senior fellow of the Discovery Institute, and is currently working with other leading researchers to interpret crucial Cambrian-era fossils unique to the Chengjiang region of China.

As you know, Homer, "Cambrian" refers to a particular era in the earth's past. It can now be said with some confidence that this era began about 543 million years ago.

With the figures put out by a team from the Massachusetts Institute of Technology (MIT), the accuracy would be something like 99.99%--and there appears to be no evidence to the contrary. What helps the accuracy is that they now have a dating method using zircon crystals.

The amazing thing is that in fossil finds dating from near the beginning of the Cambrian era--in technicalese called the "Lower Cambrian" period--we find mountains of evidence that marine animals suddenly appeared on the scene.

The major Cambrian finds are the Chengjiang Shale fossils in Yunnan, China, and the Burgess Shale fossils in the Canadian Rockies of British Columbia. These are the best in terms of preservation, variety, and accessibility.

At least a couple dozen other sites have been found all around the world; one in Greenland, another on the east coast of the United States, and another in the eastern part of the Sierra Nevada, to name a few. However, the quality of the fossils from these other sites does not really compare with those in the Burgess Shale and the Chengjiang Shale.

Some fossils on these sites were found pretty early in the 20th century. At first, paleontologists thought only simple fossils were as old as the Cambrian era.

The modern discovery actually happened in 1984. That's when complex animals were first found among the Cambrian creatures.

In the words of Dr. Paul Chien, "When we look at these early Cambrian fossils, we can conclude that roughly all the living phyla we see today were represented then.

"In fact, there were a dozen or more phyla on earth then than there are now. They seem to have gone extinct just after the beginning. So if you look at the orign of animals, in terms of phyla, or in terms of diffrent body plans, they were all there very near the beginning, all together.

"This is a significant point about the Cambrian Explosion that isn't often talked about: We see these different body plans, or different animal phyla, coming out first, before a diversity of species comes out. In other words, the development happens from the top-down instead of from the bottom-up."

In fact, one of the most respected scientists in the West, James Valentine at the University of California- Berkeley, is writing a book on this by the title of Origin of Animal Phyla, instead of The Origin of Species.

Without question, when the book is finished, it will greatly help people undrerstand what is going on. Creation is going on.

We know that the Chinese fossils were the earliest. The Western literature states the duration of the "explosion" as 5 to 10 million years--but the latest figure given by Chinese scientists in their Chinese National Geography journal [Chen Junyan et al., "The Most Remarkable Discoveries; Chengjiang Fossils," Chinese National Geography 467 (Sept. 1999): 6-25], a counterpart to our National Geographic, is 2 to 3 million years.

The explosion gets bigger and faster all the time, particularly if we look at the "width" in terms of different animals that appeared.

In the last two months of 1999, two important papers came out in the science journal, Nature. One reports that a group of Chinese scientists found over 300 specimens of a chordate they call Haikouella. [Jun-Yuan Chen, Di-Ying Huang, and Chia-Wei Li, "an Early Cambrian Craniate-Like Chordate," Nature 402 (1999): 518-22].

They think it's even more advanced than amphioxus, which now lives off the Chinese coast.

The other paper by a group of Chinese scientists and Conway Morris in English reports of what appear to be two different fish. [D-G Shu et al., "Lower Cambrian Vertebrates from South China," Nature 402 (1999): 42-46].

If they are right, we definitely have vertebrates, or fish, among those Chengjiang fossils.

Anyone know this Dr. Chien guy? He can't be that great if he's with the DI.

Patrick, you know anything about these alleged discoveries that would make Chien claim that "that roughly all the living phyla we see today were represented then" Thanks.

theyeti · 01-01-2002, 08:26 PM

Quote:

Anyone know this Dr. Chien guy? He can't be that great if he's with the DI.

Here's his bio page at the DI: <a href="http://www.discovery.org/crsc/fellows/PaulChien/index.html" target="_blank">Senior Fellow Paul Chien.</a> His PhD is in developmental and cell biology -- there's no indication that he's ever studied paleontology, so it's odd that he would be studying the Chengjiang formation except as a side project.

Most importantly, the invocation of Chien is just another argument from authority. Sure, he's got impressive credentials. But there are many hundreds of scientists with equally impressive credentials that categorically disagree with the DI. If the fact that Chien agrees with them is supposed to be evidence that they're right, then is that fact that the vast majority disagree with them evidence that they're wrong? What Chien (who is not a paleontologist) thinks is inconsequential -- it's the evidence that matters.

theyeti

[ January 02, 2002: Message edited by: theyeti ]

tgamble · 01-02-2002, 04:49 AM

Quote:

Originally posted by theyeti:
[QB]

Here's his bio page at the DI: <a href="http://www.discovery.org/crsc/fellows/PaulChien/index.html" target="_blank">Senior Fellow Paul Chien.</a> It says that he's with the University of San Fransisco and not Berkeley as your friend claims.

huh? Where'd he claim that?

It's not really what Chien says but what he bases his claims on. ie. Chengjiang Shale fossils.

MrDarwin · 01-02-2002, 05:18 AM

Quote:

Now, regarding the Cambrian Explosion, I can tell you that Dr. Paul Chien is chairman and professor of biology at the University of San Francisco. He is not only a renowned zoologist with published papers in more than 50 journals, but also has several international lecture tours to his credit.

I've been seeing these claims about Chien for so long that I finally decided to do some digging on him. According to the <a href="http://www.usfca.edu/biology/faculty.htm" target="_blank">USF Faculty website:</a>

Quote:

Research Interests: Prof. Chien is interested in the physiology and ecology of inter-tidal organisms. His research has involved the transport of amino acids and metal ions across cell membranes and the detoxification mechanisms of metal ions.

First off, please note that he is NOT department chairman. He may have been at one time (it's a bureaucratic responsibility that most scientists take on only reluctantly, as it limits their time for research) but anybody who claims that he is department chair is quoting out-of-date sources.

The second point is that while this guy is indeed a legitimate biologist he is not a paleontologist, and has not studied the Chengjiang fauna as part of his research (note that it's not even listed as one of his "research interests"). This does not necessarily disqualify him from commenting on it, but scientists are generally accorded less credibility when they write about topics outside their own specialty, and as far as I can tell, his writings on the Chengjiang fauna have appeared only in creationist publications.

Edited to add that a little more digging shows that I sold this guy short; he apparently has studied the Chengjiang fauna, and I found an abstract of one of his presentations, ironically on Precambrian organisms! See:

<a href="http://www.ucmp.berkeley.edu/napc/abs5.html#ChienP" target="_blank">SEM OBSERVATION OF PRECAMBRIAN SPONGE EMBRYOS FROM SOUTHERN CHINA, REVEALING ULTRASTRUCTURES INCLUDING YOLK GRANULES, SECRETION GRANULES, CYTOSKELETON, AND NUCLEI</a>

[ January 02, 2002: Message edited by: MrDarwin ]

theyeti · 01-02-2002, 06:22 AM

Quote:

Originally posted by tgamble:


huh? Where'd he claim that?

It's not really what Chien says but what he bases his claims on. ie. Chengjiang Shale fossils.

If you'd read the rest of my post you'd have seen that I edited to add that that was a mistake. I got him confused with someone else. I should have just changed the original, and to prevent further confusion, I will now do that. Also, the main point of my post was that it's the evidence that matters, not Chien's credentials.

theyeti

edge · 01-02-2002, 06:24 AM

Quote:

In the words of Dr. Paul Chien, "When we look at these early Cambrian fossils, we can conclude that roughly all the living phyla we see today were represented then."

Maybe I'm missing some of the subtleties of your debate, but the quote from Dr. Chien does not say that the living phyla appeared in the early Cambrian, just that they are all "represented" then. This is a BIG difference, especially with respect to the sudden appearance of the phyla. Appearance does not mean origin. It only means that this is the first record.

I have read some of these articles and they really present no problem for evolutionary theory. Having so many modern phyla represented is not a shock at all. Now, if they were the modern species, I would be surprised.

tgamble · 01-02-2002, 07:43 AM

Quote:

Originally posted by theyeti:


If you'd read the rest of my post you'd have seen that I edited to add that that was a mistake. I got him confused with someone else. I should have just changed the original, and to prevent further confusion, I will now do that. Also, the main point of my post was that it's the evidence that matters, not Chien's credentials.

theyeti

I did read the rest of your post. But it was edited right before I posted mind and I didn't edit mine. I fully agree with your point.

[ January 02, 2002: Message edited by: tgamble ]

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12-29-2001, 08:33 PM	#11
ps418 Veteran Member Join Date: Mar 2001 Location: Louisville, KY, USA Posts: 1,840	This gives me an excuse to use another quote from the Phylum Level Evolution page: There are a couple of cautions about the use of the term phyla. A phylum is assigned to a given creature based upon its having the shared characteristic body plan. Occasionally, however, different body plans are not assigned different phyla and this creates an appearance that phyla can't evolve. A case in point concerns a deep-sea sponge which is classed with the Porifera in spite of the fact that it has an entirely different body plan. Vacelet and Boury-Esnault (1995, p. 335) relate: �Our results raise fundamental questions about the validity of characteristics used to distinguish the phyla of lower invertebrates. A sponge is defined as a �sedentary, filter-feeding metazoan which utilizes a single layer of flagellated cells (choanocytes) to pump a unidirectional water current through its body. Except for being sedentary, the cave Asbestopluma and presumably all Cladorhizidae lack these basic sponge attributes. In an extreme environment where active filter-feeding has a low yield, cladorhizids have developed a mode of life roughly similar to that of foraminiferans or cnidarians. Their feeding mechanism relies on passive capture of living prey and on transfer of nutrients into the body through intense cell migrations, the analogue of cytoplasmic streaming in foraminiferan pseudopodia. This may be compared to the emergence of macrophagy in abyssal tunicates, also accompanied by a reduction of the filtering system although in Cladorhizidae the result is more extreme, with a main body plan different from Porifera and resembling no other modern anatomical design.� �Such a unique body plan would deserve recognition as a distinct phylum, if these animals were not so evidently close relatives of Porifera. Their siliceous spicules show clear similarities to several families of poecilosclerid Demospongiae.� In cases like that above, the lack attribution of phylum rank for these 'sponges' hides the fact that the Porifera may very well have given rise to an independent phyla. The only real connection between the two groups are the spicules which act as evidence of common descent. If the Cladorhizid sponges were to lose the spicules, the connection between the two groups would be lost. Body plans are obviously more of a continuum and difficult to separate than the simplistic concept of phyla espoused by anti-evolutionists would imply. Ref: Vacelet, J. and N. Boury-Esnault, 1995. �Carnivorous Sponges,� Nature, 373:333-335.

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