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Cambrian explosion: Those gaps, they just keep getting filled in, right?

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Darwin's Doubt From Darwin’s Doubt:

Over the past 150 years or so, paleontologists have found many representatives of the phyla that were well known in Darwin’s time (by analogy, the three primary colors) and a few completely new forms altogether (by analogy, some other distinct colors such as green and orange, perhaps). And, of course, within these phyla there is a great deal of variety. Nevertheless, the analogy holds at least insofar a the differences in form between ay member of one phylum and any member of another phylum are vast, and paleontologists have utterly failed to find forms that would fill these yawning chasms in what biologists call “morphological space.” In other words, they have failed to find the paleontological equivalent of the numerous finely graded interediate colors (Pendleton blue, dusty rose, gun barrel gray, magenta, etc.) That interior designers covet. Instead, extensive sampling of the fossil record has confirmed a strikingly discontinuous pattern in which representatives ofthe major phyla stand in stark isolation from members of other phyla, without intermediate forms filling the intervening morphological space.

Foote’s statistical analysis of this pattern documented by an ever-increasing number of paleontological investigations demonstrates just how improbable it is that there ever existed a myriad of as yet undiscovered intermediate forms of animal life–forms that could close the morphological distance between the Cambrian phyla one tiny evolutionary step at a time.

In effect, Foote’s analysis suggests that since paleontologists have reached repetdly into the proverbial barrel, sampled it from one end to the other, and found only representatives of vaious radically distinct phyla but no rainbow of intermediates, we should’t hold our breath expecting such intermediates to eventually emerge. He asks, “whether we have a representative sample of morphological diversity and therefore can rely on patterns documented in the fossil record.” The answer, he says, is yes.

By this affirmation, he doesn’t mean that there are no biological forms left to discover. He means, rather, that we have good reason to conclude that such discoveries will not alter the largely discontinuous pattern that has emerged. “Although we have much to learn about the evolution of form,” he writes, the statistical pattern created by our existing fossil data demonstrates that “in many respects our view of the history of biological diversity is mature. (pp. 70–71)


Morphological analysis of four higher taxa of fossil marine invertebrates shows that, over the history of paleontology, there is no general tendency for morphologically extreme or modal species and genera to be described preferentially early or late. Reconstructing the expected evolutionary sequences of morphological disparity that would have been estimated at various times during the past century and a half reveals features that are sensitive to sampling (for example, peak trilobite disparity in the Ordovician, peak of post-Paleozoic crinoid disparity in the Triassic, and peak blastoid disparity in the Permian), as well as more robust features (for example, increase in trilobite disparity from the Cambrian to the Ordovician, continued increase in trilobite disparity despite a drop in taxonomic diversity after the Early Ordovician, decrease in blastoid disparity from the Devonian to the Carboniferous, and increase in crinoid disparity from the Jurassic to the Cretaceous followed by decline during the Cretaceous). Although we still have much to learn about the evolution of form, in many respects our view of the history of biological diversity is mature.

Sampling, taxonomic description, and our evolving knowledge of morphological diversity. Paleobiology, 23: 181–206. Foote, M. 1997c.

Any big changes since then? Nope? Okay, so the gaps aren’t getting filled in.

The most likely reason now is that the gaps don’t exist. Which just mean that the history of evolution, whatever it is, is not Darwinian.

Unlike the God of Evolution, whose thundering opinion can be viewed here.

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Lincoln, To quote Foote, "Although we still have much to learn about the evolution of form, in many respects our view of the history of biological diversity is mature." Think about it. Jehu
Lincoln Phipps- Not one evolutionist can present a scientific explanation for the origin of metazoans. IOW forget the Cambrian as your position can't explain anything. Joe
If we're going to stretch the metaphor of colors then ID is magenta with missing information bracketed by differing blends of science and supernaturalism. I'll call it the SKW model - science, knowledge and woo. Evolution is changes in genotype and until modern times not only has humanity been unable to even see the genotype but as a macromolecule the genotype does not last long in geological timescales. Paleontologists really do have a fantastically difficult job to do which is akin to something like working out the familial relations by photos of the shadows of people. Actual palaeontologists are somewhat critical of Meyer's pastiche (after all Meyer writes well and so imitates the style of popular science writers and no doubt Meyer could write just as good a science book but for him being stuck in the tarpit of ID). What few fragments have been found are just lucky finds with no systemic pattern to their sampling other than reachable by humans with rock hammers and more importantly what is found is just a tiny part of the phenotype and so one step removed from the genotype, which is ultimately what evolution is all about. Lincoln Phipps
I was really hoping that Professor Matzke would be willing to have some fun speculating what genomic and fossil information would appear on a hypothetical planet identical to ours under the following conditions: - All life on the planet is engineered and seeded by university students in class projects under the direction of qualified professors. - Changes in climate and environment are assumed to be similar to the Earth. - The genomic impact and fossil records are collected for the following circumstances: a. Starting with a sterile planet. b. Starting with a vegetation-covered planet, or perhaps a food-chain introduction sequence of appropriate species. c. Data is collected after: 10K, 100K, 1M, 10M, 100M, 1B years. d. There's a possibility of rogue projects. Anyway, I thought it might evolve into an interesting discussion, but Professor Matze apparently did not take this proposal seriously and declined to participate. Too bad. -Q Querius
The most likely reason now is that the gaps don’t exist. Which just mean that the history of evolution, whatever it is, is not Darwinian.
I guess that is possible depending on how you define "evolution", but there is another way to interpret the evidence. The kind of molecules to man evolution that Darwin and most people today believe in actually never occurred. The gaps are found in the fossil record because they actually exist. God created everything according to it's "kind", (not meaning that He created each individual species that exists today in the beginning). We see evolution or perhaps speciation/adaptation within these original kinds, but not across the border lines of the original kinds. The gaps between the kinds exists because the gap was never crossed by any evolutionary process. Of course, defining the original kinds is a difficult task. We may never be able to accurately come up with that answer, but as the gaps become more and more clear, that should help. Interpreting the evidence from the past is notoriously difficult and new discoveries often show us that our previous interpretations were wrong. We're dealing with history here and we never know if we have all the relevant necessary information in order to make an accurate interpretation or not. And even if we did, we have biases that effect our interpretations so this stuff cannot be/should not be classified as "scientific knowledge", but should be seen as our best current guess. When pressed, scientists admit this, but mostly this truth is forgotten and interpretations of the evidence are seen to be the only accurate dependable source of knowledge that we have. That is so wrong! tjguy
Of course, we are still waiting for our prevaricating friend Nick Matzke to show us the evidence for the finely graduated intermediate fossils between Precambrian shellies and Cambrian trilobytes. I guess we'll have to wait for chickens to grow teeth and evolve into fierce predatory birds. Mapou
Is there any combination of facts that can ever disprove The Theory of Evolution? Even the Flat Earth folks eventually accepted that Round Earth fit the observations better. Oh, I forgot. Evolution is the Creation Myth of Atheists. If they ever renounce their Myth, the rest of their religion collapses. mahuna

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