Message 1 of 137 (486407) 10-20-2008 1:57 AM

I haven’t seen a thread devoted entirely to the Cambrian Explosion for awhile, even though the topic has come up often in passing in many different threads. I particularly like the Cambrian Explosion, because, as an entomologist and a long-time science-fiction fan, I have always been interested in bizarre creatures, and the Cambrian Explosion has its share of bizarre creatures, such as Opabinia regalis (my personal favorite).

So, what does everyone think about the Cambrian Explosion?

As most of us know, creationists will often cite the apparently rapid radiation of animal groups around the beginning of the Cambrian period as evidence against the uniformitarian principles that scientists generally consider prevalent in the processes of evolution. Often, however, reference to the Cambrian Explosion is only made in passing, and no major attempt is made to explain its relevance in the thread. So, I propose this thread to discuss the role of the Cambrian Explosion in the evolutionary and ID models of natural history.

I argue that the Cambrian Explosion does not evidence a special creation. I would like to explore perhaps three main themes:

1. The Phyla Argument: Creationist claims inflate the drama of the event by pointing out that all modern phyla appear within 50 million years, while failing to note that the difference between phyla at the time was far less than the difference between their descendants today. This was discussed rather thoroughly here, so it need not be emphasized in this thread: I included it so that it wouldn’t be simply overlooked.

2. The Pace Argument: Creationists claim that the “rapid” appearance of a diverse fauna must be interpreted by evolutionists as an unrealistically fast rate of change, and that it is thus better explained as an untransitioned, spontaneous creation. However, I contend that mutations need not have happened at a higher rate than today, because the lower diversity in the fauna would have lowered competition and allowed a greater proportion of the mutations that occurred to survive and accumulate. Aside from this, there may not be any support for the claim evolution during the Cambrian Explosion happened at a faster pace, anyway.

3. The Snapshot Effect: Creationist claims of suddenness for the Cambrian Explosion are also compounded by the “snapshot” effect. Claiming that the appearance of Cambrian shelly fauna in only a handful of locations is evidence of spontaneous creation is akin to claiming that the discovery of only a single praying mantis in a field indicates that said mantis must have been created by God, because there was nothing around it for it to have evolved from.

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I would be interested in hearing creationists' response to the last two points (let's save point #1 for emergencies, such as if the thread dies down too early, or something).

Edited by Adminnemooseus, : Fix URL - There was a space bunging it up.

Darwin loves you.

Message 3 of 137 (486419) 10-20-2008 9:48 AM

Reply to: Message 1 by Blue Jay 10-20-2008 1:57 AM

the prtostome phyla before the Cambrian:

Chaetognatha - Arrow worms
Tardigrata - Water Bears
Onychophora - Velvet Worms
Arthopoda - Insects, crustaceans, arachnids etc.
Cephalorhynchs - no common name
Nematoda - Round worms
Nenatophora - Hairworms
Gnathifera - Rotifers
Platyhelminthes - Flat Worms
Brachiozoa - Brachiopods (lamp shells)
Entoprocta - Goblet Worms
Bryozoa - Moss Animals
Nemertea - Ribbon Worms
Mollusca - Clams, squid, octopi etc.
Annelida - Segmented worms
Sipunculoidea - Peanut worms

All of these phhla existed before the so called Cambrian Explosion.

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Message 4 of 137 (486443) 10-20-2008 4:29 PM

Reply to: Message 1 by Blue Jay 10-20-2008 1:57 AM

First, this so-called "explosion" took place over several tens of millions of years -- hardly instantaneous, and certainly not consistent with the Genesis account.

Second, as you point out, there is a much longer fossil record that extends much, much farther back before the Cambrian. Also, the current genetic evidence indicates that the splitting of the major phyla occurred well before the Cambrian.

Finally, there is not a single example of an indisputably modern life-form that is found from the time of the Cambrian explosion. Even those species that can be identified with extant taxa are very different from the modern forms.

In short, there is nothing to explain. In fact, it is the YEC who has to explain why, if this is supposed to be a record of the Genesis event, why there are no modern life forms, why life forms are dated much earlier than the Cambrian, and why the Cambrian Explosion is dated to a very wide range of time -- the same explanations that the YEC has failed to provide to geology in general.

Message 5 of 137 (486471) 10-21-2008 5:29 AM

Reply to: Message 3 by bluescat48 10-20-2008 9:48 AM

quote:

---

Chaetognatha - Arrow worms
Tardigrata - Water Bears
Onychophora - Velvet Worms
Arthopoda - Insects, crustaceans, arachnids etc.
Cephalorhynchs - no common name
Nematoda - Round worms
Nenatophora - Hairworms
Gnathifera - Rotifers
Platyhelminthes - Flat Worms
Brachiozoa - Brachiopods (lamp shells)
Entoprocta - Goblet Worms
Bryozoa - Moss Animals
Nemertea - Ribbon Worms
Mollusca - Clams, squid, octopi etc.
Annelida - Segmented worms
Sipunculoidea - Peanut worms

---

Most of those are not Phyla.

Message 6 of 137 (486472) 10-21-2008 6:11 AM

Reply to: Message 3 by bluescat48 10-20-2008 9:48 AM

You sure about that? Based on what data? Bryozoans don't turn up in the fossil record until the ordovician, the period after the cambrian.

Mark

Message 7 of 137 (486477) 10-21-2008 8:24 AM

Reply to: Message 5 by Dr Jack 10-21-2008 5:29 AM

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Message 9 of 137 (486482) 10-21-2008 9:04 AM

Reply to: Message 6 by mark24 10-21-2008 6:11 AM

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Message 10 of 137 (486513) 10-21-2008 7:57 PM

Reply to: Message 9 by bluescat48 10-21-2008 9:04 AM

I must confess I'm not a scientist--nor do I know much about this stuff. But, I, as a plain layman, can't understand scientists concluding about a "common ancestor".

They discover common parts of certain animals or what not and they say "common anscestor". I can't be convinced by that. To my mind, there are other valid conclusions about this "common parts" (Homologous, is that correct?:
1) why not common ancestorS as in PLURAL?
2) why not common parts as evidence of a common designer--e.g. a Civic having common parts as Accord is evidence of common designer, HOnda? ( Of course, the draw back is the identity of the designer again... and that is admitted. But, why not designed by an unknown designer? )

3) Why not just Stop this conclusion: 'in our investigation of the fossil we found animals, plants, etc of having ALMOST similar parts?'

I have done a little bit of research on the so called "phylogenitic tree", and I am not convinced of the conclusion reached--common ancestor. All I can see are common parts. Are there not big gaps in this so called theory about "common ancestor"?

Edited by Doubting Too, : No reason given.

Message 11 of 137 (486515) 10-21-2008 8:14 PM

Reply to: Message 10 by NOT JULIUS 10-21-2008 7:57 PM

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Message 12 of 137 (486516) 10-21-2008 8:16 PM

Reply to: Message 4 by Chiroptera 10-20-2008 4:29 PM

A reference material, A View of Life, says: "Beginning at the base of the Cambrian period and extending for about 10 million years, all the major groups of skeletonized invertebrates made their first appearance in the most spectacular rise in diversity ever recorded in our planet." I understand that in that period, snails, sponges, starfish, tribolites (lobster like animals) and many other complex sea creatures appeared. Interestingly, the same book observes: "some extinct tribolites, in fact, developed more complex and efficient eyes than any living anrthoropod posseses"

Message 13 of 137 (486519) 10-21-2008 10:21 PM

Reply to: Message 12 by NOT JULIUS 10-21-2008 8:16 PM

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Message 14 of 137 (486523) 10-22-2008 4:53 AM

Reply to: Message 10 by NOT JULIUS 10-21-2008 7:57 PM

In an evolutionary context, an ancestor is quite literally a genetically related individual. So you should not think of ancestors as merely a group of forebears, in the sense of "the people who went before us", related or not.

If you trace your ancestry and that of your third cousin twice removed, you will normally find that the both of you share two common ancestors: your great great grandfather and his wife, your great great grandmother. Your third cousin twice removed will call them great great great great grandfather and ditto grandmother - she is twice removed, hence the two extra greats. However, it could be that your great granduncle - your third cousin twice removed's great great great grandfather, but no direct ancestor of yours - is the son of your great great grandfather and his second wife. In that case you share literally only one common ancestor with your third cousin twice removed.

In asexually reproducing species an organism always has one parent, one grandparent, one great grandparent, and so on. In sexually reproducing species, it is by no means guaranteed that an individual always mates with the same partner. So, although there is the possibility that two distantly related organisms share two common ancestors, it is more practical to consider just one. So, you can literally speak of just one individual common ancestor you share with the orangutan you stare in the face in the zoo. This common ancestor lived millions of years ago and was neither a human, nor an orangutan. Much much longer ago, there lived another individual animal who was the common ancestor between you and your dog. Again, this ancestor was neither a human nor a dog. The more different the two organisms under consideration are, the further back in time their common ancestor will have lived, and the less it will have looked like either of them. But every time you consider such a common ancestor, you should be aware of the fact that it must be, of necessity, literally one individual (or at most two).

The phylogenetic tree is by no means the only evidence we have for the theory of evolution. All kinds of other evidence point to evolution instead of design. Besides, even the phylogenetic tree in itself is poor evidence for design. In design, if a feature does not meet requirements, it is customary to make a significant change instead of an ever so gradual movement in a certain direction. Also, we would not expect obvious mistakes, like the blind spot in the human eye, or the problematic use in bipeds of a backbone "designed" for quadrupeds, to be left untouched by a designer.

That is not a conclusion, it's just a starting point of some very interesting scientific research. If you want to stop there, why would you even want to begin to investigate in the first place?

If a Caucasian woman gives birth to a child with dark skin and black curly hair, I don't suppose her Caucasian husband is going to say "Well, all I can see are common parts between my child and African people. There's no reason to suspect that my wife has been unfaithful." Would you?

Animal and plant breeding rely on the principle of common ancestry. If you think there was nothing to it, how do you suppose to explain its success?

There will always be gaps in human knowledge, but they are getting smaller and smaller. As far as the theory of evolution is concerned, lots of corroborative evidence is available from many different disciplines. The great thing about these different lines of evidence is that they all fit with the theory, they all point to the same conclusion: evolution by random mutation and natural selection is what really happened.

Edited by Parasomnium, : No reason given.