ps418

Let me try to clear things up a little bit. The points I made are not being addressed. First let me say that I am not denying that most phyla originated during the early Cambrian. We know for a fact that most skeletonized phyla appeared then. Bryozoa appear in the Ordovician, which contradicts what MrOEC stated:

The statement that prompted me to post was mainly this one:

Fossils previously found in Yunnan province (at sites discovered nearly 100 years ago) and in the Burgess Shale deposits of the Canadian Rockies tell us that all animal phyla (more than 70) ever to exist in Earth's history appeared "at once" about 540 million years ago.

Now, this statement is just plain wrong. It is an inexcusable exaggeration of the evidence. First of all, the Chengjiang deposits from Yunnan are dated to 518Ma, while the Burgess Shale is dated to 506Ma [all dates here are from Babcock, Zhang, and Leslie. GSA Today, The Chenjiang Biota, Feb. 2001, which cites the most recent literature].

So, there's an error right there. However, Babcock et al do state that 10Ma, 521-511Ma is the period during which most durably skeletonized phyla appear. However, 10Ma is not "all at once," and most extant phyla is not all extant phyla.

Second, for the 51st time now, ALL EXTANT PHYLA DO NOT APPEAR IN THE EARLY CAMBRIAN! Let me repeat that one more time: ALL EXTANT PHYLA DO NOT APPEAR IN THE EARLY CAMBRIAN! This is the main point of contention on my part, and I havent seen a retraction from MrOEC yet.

Several of the phyla are now demonstrated in precambrian deposits, including sponges, cnidarians, and stem-group triploblasts whose assignment is not certain. See:

Simon Conway Morris, Special Feature: The Cambrian "explosion": Slow-fuse or megatonnage?
PNAS 97: 4426-4429.

Accoring to Knoll and Carroll:

Earliest Cambrian assemblages contain few taxa, and the diversity of trace and body fossils grew only over a protracted interval. Hyoliths and halkierids (extinct forms thought to be related to mollusks), true conchiferan mollusks and, perhaps, chaetognaths enter the record during the first 10 to 12 million years of the Cambrian, but crown-group fossils of most other bilaterian phyla appear later: the earliest body fossils of brachiopods, arthropods, chordates, and echinoderms all post-date the beginning of the period by 10 to 25 million years. Trace fossils suggest earlier appearances for some groups, notably arthropods, but the observation remains that the Early Cambrian contains considerable time for the assembly and diversification of crown group morphologies.

This is the whole point Im trying to make -- whereas creationists would like to believe that everything appears all at once, the evidence indicate that first appearances of extant phyla-

-for instance, sponges at ~570Ma (Doshounto Formation) and bryozoa at ~490Ma--

-originated at different times. This is not to deny that the Cambrian radiation saw the first appearance of many phyla.

Now, the quote says:

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.

We can conclude on what basis? Not on the basis of finding actual fossils of all phyla at Chenjiang! And what does roughly mean? One half? Two thirds? Three quarters?

Here is a list of all the phyla known from the Burgess Shale, according to RIggs, Erwin, and Collier, Fossils of the Burgess Shale, 1994, p. 217-221:

Porifera
Cnidaria
Ctenophora
Lophophorata
Mollusca
Hyolitha
Priapulida
Annelida
Onychophora
Arthropoda
Echinodermata
Hemichordata
Chordata

That's 13 of the ~30 extant animal phyla known from fossils in the Burgess Shale.

According to Babcock, Zhang, and Leslie. GSA Today, The Chenjiang Biota, Feb. 2001, the same phyla are represented at Chenjiang, except that mollusca and echinodermata are not represented, which indicates that 11 of 30 extant animal phyla are represented there.

So, all I need from your friend now, what I explicitly asked for in the first place, is where I can find descriptions of the other ~17 animal phyla in early Cambrian deposits. For instance, were are the:

Nematoda
Nemertini
Entoprocta
Rotifera
Placozoa
Platyhelminthes
Gnathostomulida
Gastrotricha
Acanthocephata
Loricifera
Kinorhyncha
Pogonophora
Sipuncula
Phoronida
Vestimentifera

Remember, I'm not saying they existed or didnt exist in the early Cambrian. I'm saying there's no fossil specimens proving that they originated "all at once" in the early Cambrian.

[ January 02, 2002: Message edited by: ps418 ]</p>

ps418

The top-down pattern is a consequence of the way organisms are classified in Linnaean taxonomy. According to Keith Miller:

Battson emphasizes the pattern of appearance of higher taxa in which phylum-level diversity reaches its peak in the fossil record before class-level diversity, and class-level diversity before that of orders, etc.10 Battson and other critics of macroevolution interpret this apparent "top-down" pattern as contrary to expectations from evolutionary theory. However, this pattern is generated by the way in which species are assigned to higher taxa. When a hierarchical classification is applied retrospectively to a diversifying evolutionary tree, a "top-down" pattern will of necessity result. Consider, for example, species belonging to a single evolving lineage given genus-level status. This genus is then grouped with other closely related lineages into a family. The common ancestors of these genera are by definition included within that family. Those ancestors must logically be older than any of the other species within the family. Thus the family level taxon would appear in the fossil record before most of the genera and species included within it. The "top-down" pattern of taxa appearance is therefore entirely consistent with a branching tree of life.

ps418

Here are some quotes from Hughes NCSE article <a href="http://www.ncseweb.org/resources/rncse_content/vol20/5545_creationism_and_the_emergence__12_30_1899.asp " target="_blank">Creationism and the Emergence of Animals: The Original Spin:</a>

The bottom line is that the establishment of modern animal groups was a protracted affair that began no later than about 600 million years ago, extended across the Precambrian-Cambrian boundary, was still in progress during the Early Cambrian Epoch, and continued after the close of the Cambrian Period. Accordingly, science currently tells us that there was, at a minimum, about 100 million years from the time when the first sponge-like animals originated until the origin of representatives of all the major living lineages or body plans.

Oh, and I also was not able to find a single article on the Chengjiang fauna authored by Paul Chien.

edge

I think that there may be some confusion here. "Appearance" in the fossil record does not mean "origination." It means that it is the earliest time that we see something that may have existed before. That is how some paleontologists use the word. Second, I'm not sure that Chien is being quoted in context here. He may have been referring to all Cambrian fossils spread out over tens of millions of years of Cambrian time. As I said, I read two of his papers once when this came up before and it really did not give me the impression that he was arguing for a geologically instantaneous creation of large numbers of phyla.

I think the fact that he says "represented" does not necessarily mean that he thinks these organisms originated at that time. Not being a paleontologist is a bit of a hindrance to me, but I think that Chien is being misrepresented by creationists. Not that I've ever seen that before. "

MrDarwin

Let Chien speak for himself:

<a href="http://www.discovery.org/articleFiles/PDFs/Cambrian.pdf" target="_blank">The Cambrian Explosion: Biology's Big Bang</a> (paper coauthored by Paul Chien, pdf file)

<a href="http://www.origins.org/real/ri9701/chien.html" target="_blank">Explosion of Life</a> (interview with Paul Chien)

[ January 03, 2002: Message edited by: MrDarwin ]</p>

tgamble

the paper seems to be outdated.

I remember reading about fossil worms that were 1 billion years old. Worms are multicellula aren't they?

edge

Thanks for the links. I guess I had only read the peer-reviewed stuff that just described the Chinese fossils. Did someon say what the backgrounds of these authors are?

As far as being out of date, the first article is dated 2001. I think the real problem is lack of sound geological reasoning.

[ January 03, 2002: Message edited by: edge ]</p>

MrDarwin

Note that the authors go to great pains to minimize (a) the 10 million years (!) of phyletic diversification, as well as (b) the presence of multicellular animals, including some modern phyla, in Precambrian sediments.

The truly amazing thing is that YEC's cite such articles as if they actually supported the YEC position!

tgamble

well, they help cast doubt on evolution. YECs aren't really concerned with the details.

edge

With all due respect to the good doctor, I think he needs a stronger background in geology. The authors of the article seem to see a snapshot of life in the early Cambrian and disregard what happened before and after. They do not see all of the data around them. They indeed dismiss substantial stretches of geological time as "one minute out of a day," but forget that we are talking tens of millions of years! The main point to me, however, is that the period of diversification prior to the early Cambrian could be substantially longer than that and the Cambrian "Explosion" may have been exaggerated. Actually, that was my first (excited) impression when I first read about some of the recent fossil discoveries. Then I remembered some of my professors saying similar things (too long ago) regarding the Cambrian Explosion: that it may just be apparent. In fact I don't remember even calling it an "explosion" back then.

And yes, there were multicellular organisms in the Proterozoic and many of them could be interepreted to be forerunners of the same body plans that we see later in the Cambrian. This is just my opinion, though. And the time difference between the Ediacaran fossils and the Cambrian explosion was on the order of 30 million years, if I remember correctly. Not a trivial span.

But then what is 5 or more orders of magnitude among friends? By the way, does anyone else here get the impression that the IDists are far more dogmatic and ardent than your regular, every day creationists? A large percentage of the most ill-humored, and hypersensitive people on these boards seem to be confirmed IDists.