The Cambrian Explosion

[otseng]

[youngborean]

It turns out that much of the ocean floor is quite new.

I guess this was the crux of my point. I thought your explanation was saying that Burgess was the Ocean floor pushed upwards. This is how I understand it. That Burgess was a reef that got push up. Not recycled volcanic material that wen't down then shot up though a volcano like the mountains down in Mexico.

Usually, fossils are in rock that can't be dated directly. One must rely on dating the "datable" strata above and below, which gives an age-range for the fossil. There are creationists who say this isn't valid either, because it doesn't date the fossil...but it's the same principle as finding a house on a street when you know the addresses two blocks north and two blocks south. Interpolation is valid methodology.

Weren't the Burgess fossils found on the surface of the Rockies? How can we interpolate the surface? That was the point I was attempting to reach in my earlier post.

Having said this, the Cambrian Explosion is often (erroneously) thought of as a very sudden appearance, all at once, of many species. At the level of resolution that we are talking about, "all at once" is probably at least 10 million years. If we include the rapidly-increasing knowledge of Precambrian fossils, then we must increase the length of time for this "explosion" considerably. Maybe we're talking 50 or 100 million years. I dunno...that seems like a long time to me.

A long time to me as well.

[Jose]

I guess this was the crux of my point. I thought your explanation was saying that Burgess was the Ocean floor pushed upwards. This is how I understand it. That Burgess was a reef that got push up. Not recycled volcanic material that wen't down then shot up though a volcano like the mountains down in Mexico.

Aha! I see now. The Rockies are partly volcanic, and partly sedimentary. As "granitic intrusions" pushed upward toward the surface, the sedimentary rock on the surface was pushed upward as well. In this case, the surface was the continental plate that had previously been pushed under water, long enough for sediment to form on it. If the granitic intrusions reach the surface, we get volcanic eruptions. If they don't, we get big granite "roots" (if you will) of the mountains.

On the east side of the Rockies near Denver, it is easy to see the sedimentary strata becoming tilted more and more as the mountains become taller. On the west side, say around Grand Junction or Dotsero, the whole sedimentary "layer cake" was lifted up without much tilt to it. The cliffs that formed as the rivers carved through these "layer cakes" show the various strata quite clearly.

Weren't the Burgess fossils found on the surface of the Rockies? How can we interpolate the surface? That was the point I was attempting to reach in my earlier post.

Again , aha! I haven't been to the Burgess Shale, so I can't describe it firsthand. But, my understanding is that it is like sedimentary outcrops that I have seen, which are like these "sliced layer cakes." The "surface" is the side of a cliff, or a steep mountainside. Upper layers are at higher elevation, up the cliff, and lower layers are down the cliff. It actually makes sense. (!)

[otseng]

How does the data from the Cambrian Explosion argue for/against the creation model(s)?

The evidence of the Cambrian layer (Cambrian explosion) shows that almost all the modern phyla are found there. This is consistent with creationism since it says that all the phyla were created at the beginning.

In creationism, it is possible for phyla to become extinct over time, but no new phyla can be introduced over time. This is also evidenced by the fact that many phyla in the Cambrian layer existed but has since become extinct.

Creationism postulates that a global flood was the mechanism to cause the formation of the Cambrian layer (as well as all the geologic layers). If a global flood occurred, one would expect that the lowest layers would have a lot of different types of life buried, which is what we see in the Cambrian layer.

Thus, by looking at the arguments against the evolutionary models and arguments for the creation model, creationism offers a more viable explanation of the Cambrian explosion than does evolutionism.

[Jose]

The evidence of the Cambrian layer (Cambrian explosion) shows that almost all the modern phyla are found there. This is consistent with creationism since it says that all the phyla were created at the beginning.

In creationism, it is possible for phyla to become extinct over time, but no new phyla can be introduced over time. This is also evidenced by the fact that many phyla in the Cambrian layer existed but has since become extinct.

Hmmm...it is interesting to note that the "Cambrian explosion" argument refers to the "major phyla." If we include the minor phyla, we see that roughly half of the animal phyla showed up later. Now, we can argue that the later-evolving phyla were actually present for millions of years before the first identifiable fossils showed up, and thereby claim that they, too, were part of the Cambrian "explosion." If we do, however, we have to use the same logic with the other fossils of the Cambrian, and recognize that their ancestors must have been around for millions of years before they developed hard parts that could be readily fossilized. So, either the Cambrian "explosion" actually occurred over many years before the development of shells, or other phyla appeared later.

By "many years," I refer to the current estimate of 600 million, rather than the measley 10 million that is usually meant by the Cambrian "explosion." Even a 10 million year explosion is pretty slow compared to the predictions of creationism.

Another interesting point: the Cambrian explosion doesn't apply to plants at all. They have a different history, with new phyla (called divisions by botanists) appearing much later.

Creationism postulates that a global flood was the mechanism to cause the formation of the Cambrian layer (as well as all the geologic layers). If a global flood occurred, one would expect that the lowest layers would have a lot of different types of life buried, which is what we see in the Cambrian layer.

One would also expect that this layer would have representatives of the things that are buried in upper layers, which it does not. Virtually everything that existed in the Cambrian has gone extinct, and has been replaced with entirely different things. This is most easily explained by Wen The Eternally Surprised, as God re-creating the world each instant. that way, God can put in new species as needed. Another way to explain it, of course, is by evolutionary mechanisms, which would give the result that we see.

Hmmm...your mention of the global flood reminds me that part way throughthe global flood thread, we had made some predictions based on the model, so that we could evaluate it and see how well it would fit in science classes. How's the research going, to assess whether those predictions are borne out?

[otseng]

How's the research going, to assess whether those predictions are borne out?

It has not slipped my mind. I have placed on order a couple of the books that rjw mentioned - Oceanography: An Introduction to the Planet Oceanus and Understanding Earth. My understanding of the earth sciences is very limited, so I hope to have the chance to read them when I get them and do further learning/research.

[keltzkroz]

[gluadys]

[Jose]

We don't expect to see new phyla developing today, because there is no real advantage to a unicellular creature which has survived successfully to the present to become multicellular and compete with multicellular creatures that have been around for half a billion years already.

That could change if some future disaster destroyed the bulk of multicellular life.

...in other words, any incipient new phyla that might begin to emerge would be out-competed by the existing species that are already highy efficient at making a living in their particular niches. Newcomers tend to be less-well adapted, and cannot easily displace those who are already there. Hence, major evolutionary shifts often follow mass extinctions--like the diversification of mammals only after the extinction of the dinosaurs. Or, they follow adaptive innovations that open up new possibilities--like the colonization of land.

At present, the world is pretty full of advanced microbes and advanced multicellular plants and animals. There's a lot of competition for the new guy on the block.