Tuesday, May 10, 2005

Pounding the Table

There is a saying among lawyers: “When the facts are on your side pound the facts. When the law is on your side pound the law. When neither is on your side pound the table.”

This is a lesson ID proponents have learned well. Since the basic facts of science are unambiguously on the side of evolution, they must make do with pounding the table.

Take, for example, this essay by ID proponent Jonathan Witt that recently appeared in The Kansas City Star.

It seems that Witt is too busy to come up with his own bad arguments, so he chooses instead to parrot Jonathan Wells' arguments from Icons of Evolution. In doing so Witt has chosen not to be hindered by petty considerations like a concern for the truth. Consider:

More than 140 years of assiduous fossil collecting has only aggravated the problem. Instead of slight differences appearing first, then greater differences emerging later, the greatest differences appear right at the start — numerous and radically disparate anatomies leaping together onto the Cambrian stage. These aren't just distinct species but distinct phyla, categories so large that man and bat occupy not only the same phylum but the same subphylum. Later geological periods show similar patterns of sudden appearance, stasis and persistent chasms of difference between major groups.

Let's begin with the obvious: The Cambrian fossils are not “right at the start” of anything. Life already had a roughly three billion year history on Earth prior to the Cambrian era. In particular, we now have numerous Precambrian fossils that show clear relationships with those from the Cambrian.

The next point is that every fossil, Cambrian or otherwise, is a species and that is all. It represents the remains of a long dead organism that was making a living in some bygone era. That every fossil must be classed within some phylum is simply an artifact of our system of taxonomy. The conventions of paleontology require that when a new fossil is found it must be assigned to some phylum; either to one that already exists or to a new one created just for that fossil. This creates an illusion of “Top Down” design that freshman geology majors find easy to penetrate, but which is apparently too powerful for people like Witt.

To see this another way, try to picture the tree of life. It begins with the universal common ancestor (whether this ancestor was a single species or a community of gene-trading cells will not concern us here). From this point life begins to diversify and spread out. We can imagine drawing this tree in some systematic way so that the distance between branches is roughly correlated with the morphological differences between the organisms at the ends of those branches.

Picture the species at the earliest branching points in the tree. Though they go on to produce wildly different branches of life's, at this point they are still very similar.

Millions of years later human beings arrive on the scene. Life has now diversified to the point where we have wildly different sorts of life, such as humans, fungi and bacteria. In their attempt to impose some order on this chaos humans invent a system of taxonomy and use it to classify existing organisms.

These humans then discover that the fossil record supplies copious examples of species that no longer exist. It seems natural to nonetheless try to fit them in to the taxonomic hierarchy that works reasonably well for living organisms. This involves assigning each fossil to a phylum. To do that, you look for features of particular fossils that in modern organisms are representative of different phyla. Minus any such features, you assign the fossil its own, brand-new phylum.

What will be the effect of this process? When we look back at the ancient fossils of the Cambrian we find some have features sufficiently distinct to allow us to place them in modern phyla. But in terms of the tree of life, all of the species that existed during the Cambrian were evolutionarily very close to each other. That they may have possessed certain features that, millions of years later will be used by humans as diagnostic of different phyla does not change the fact that they were still evolutionarily very close.

So the idea that placing different Cambrian fossils in different phyla implies that they are as different from each other as humans are from bats is simply ridiculous. If my explanation was too long-winded, have a look at this excellent summary by Alan Gishlik, available here:

Another reason why the “higher” taxonomic groups appear at the Cambrian Explosion is because the Cambrian Explosion organisms are often the first to show features that allow us to relate them to living groups. The Cambrian Explosion, for example, is the first time we are able to distinguish a chordate from an arthropod. This does not mean that the chordate or arthropod lineages evolved then, only that they then became recognizable as such. For a simple example, consider the turtle. How do you know a turtle is a turtle? By the shell. How would you recognize the ancestors of the living turtle, before they evolved the shell? That is more complicated. Because its ancestors would have lacked the diagnostic feature of a shell, ancestral turtles may be hard to recognize (Lee, 1993). In order to locate the remote ancestors of turtles, other, more subtle, features must be found.

Similarly, before the Cambrian Explosion, there were lots of “worms,” now preserved as trace fossils (i.e., there is evidence of burrowing in the sediments). However, we cannot distinguish the chordate “worms” from the mollusc “worms” from the arthropod “worms” from the worm “worms.” Evolution predicts that the ancestor of all these groups was worm-like, but which worm evolved the notochord, and which the jointed appendages?

Witt simply has no basis for his claim that the fossils of the Cambrian were radically different from one another.

Recently I've been writing quite a bit about why evolutionists get so angry when dealing with ID folks. So far I've been focussing on the creationist habit of removing quotes from their proper context, and that is certainly one big reason for the anger. But another reason is that ID folks routinely mangle very basic points of evolutionary theory. It is a lot easier to spew nonsense than it is to correct it. This fact, coupled with the complete shamelessness of ID proponents, works to ID's advantage in the PR battle.


At 9:05 AM, Blogger RPM said...

We can imagine drawing this tree in some systematic way so that the distance between branches is roughly correlated with the morphological differences between the organisms at the ends of those branches.

Technically, we measure the distance between tips and/or nodes (not branches). This may seem like a trivial point, but it is extremely important because the branches themselves are the distances between tips and/or nodes.

For example, say you have two line segments connected at one of each of their tips. You would not measure the distance between those line segments, but, rather, the distance between the tips of an individual line segment (i.e., tip to node) or the distance between the two non-adjoining ends of the two line segments (tip to node to other tip).

I'm sorry that this entirely of topic from the rest of your post. I think you make an important point about the artificiality of taxonomic classification and the limitations of the fossil record. Thankfully, we have comparative genetic data that supports evolution as well.

At 12:29 PM, Anonymous Anonymous said...

There is a new tendency among creationist to try to inoculate themselves against the results of science. The best example I know is from a deeply flawed Op Ed piece by Mark Hartwig's, "Science by Design," in the April 24, 2005 issue of the York Daily Record. Hartwig says,

"Of course, what’s important here is not what we conclude about the flagellum or the cell, but how we study it."

Of course, what we conclude is important but if you can convince people that it isn't then you can say the same old nonsense over and over and it will not matter a bit.

As Mark Twain once said, in the June 16, 1867 Alta California, "The most outrageous lies that can be invented will find believers if a man only tells them with all his might."

At 2:28 PM, Blogger Jason said...


Thanks for the correction. It's a minor point, but I hsould have been more careful. Thank you for pointing it out to me.

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