The Mystery of the Missing Fossils
Darwin is to be commended for recognising that the fossil record did not endorse his gradualist approach to the origin of species. The abrupt appearance of each different type of animal and plant was known to his peers as a pervasive characteristic. He found a way of reconciling this empirical evidence with his scenario of evolution by natural selection: the extreme impoverishment of the fossil record. Yet even this did not do justice to the observation that a great disparity of hard-bodied animal life is to be found in the "lowest known fossiliferous rocks", below which are apparently barren strata. As a difficulty for his theory, Darwin described it as "very great".
In his introduction to the issues, Meyer recounts the discourse between palaeontologist Louis Agassiz and Charles Darwin. Agassiz was not convinced that natural selection acting on small variations could achieve much in the way of transformation, and he considered the abrupt appearance of animals as an argument against Darwinism. Meyer looks closely at the issues highlighted by Agassiz, and reinforces them by discussing the views of two other leading geologists: Murchison and Sedgwick. He establishes that the issues were worthy of discussion by the leading scholars of Darwin's day and that Darwinism did not supply satisfactory answers to legitimate questions.
Agassiz insisted that Darwin's picture of the history of life "contradict[ed] what the animal forms buried in the rocky strata of our earth tell us of their own introduction and succession upon the surface of the globe. Let us therefore hear them; - for, after all, their testimony is that of the eye-witness and the actor in the scene." (cited on pages 12-13)
So, to test Darwin's hypothesis, it was necessary to search for relevant strata and study their organic remains in more detail. The quest for ancestors of the Cambrian animals thus became a major issue for students of earth history. The first big find was in 1910, when fossils of the Burgess Shale greatly expanded knowledge of animals living in the Middle Cambrian Period. Meyer shows that the discovery amplified the tension between Darwinism and the fossil record because the observed diversity of phyla and classes was not at all what theory predicted. Those familiar with Gould's "Wonderful Life" will already be aware of the mismatch between theoretical predictions and empirical evidence. However, as Darwinism was dominant in 1910, an explanation of the discrepancy was needed that would respond to the challenge of Agassiz. It emerged as the "Artifact hypothesis": the ancestral animals were evolving in deep sea waters away from continental land masses, so that these ancestral forms still awaited discovery.
The next spotlight shone on the fossil record illuminates the multicellular organisms prior to the Cambrian Period. These are known as the Ediacaran fauna, but no one is sure what they are. Despite this, Darwinists have tended to regard these organisms as evidence of a fuse leading to the Cambrian Explosion. However, such ideas cannot be regarded as having scientific weight. This is because the Ediacarans do not have the diagnostic features of animals, there are no linkages which support animal ancestry, gradualism is not in evidence and the timescales are inadequate. Meyer provides a powerful quote from two specialists in the field:
"The expected Darwinian pattern of a deep fossil history of the bilaterans, potentially showing their gradual development, stretching hundreds of millions of years into the Precambrian, has singularly failed to materialise." (page 96)
If fossils are not documenting the story of the origin of animals, are there other clues for researchers to follow? Meyer turns his attention to the way genetic information has been used to map the Precambrian-Cambrian tree of life. Researchers regard sequence similarities as a witness to common ancestry, and sequence differences as evidence that can be used to determine the timescales involved. Such studies usually extend the origins of the animal phyla many hundreds of millions of years, and the emerging phylogenetic trees are used to cast doubt on the idea that the Cambrian diversification was explosive. Meyer argues that there is a methodological problem relating to the interpretation of data. Evidence supporting this claim is provided by the conflicting divergence times. At the root of the problem are questionable assumptions: the constant ticking of molecular clocks, and the descent of all animal forms from a common ancestor.
"Thus, the deep-divergence studies do not, in any rigorous sense, establish any Precambrian ancestral forms. Did a single, original metazoan or bilateran ancestor of the Cambrian animals actually exist? The Precambrian-Cambrian fossil record taken on its face certainly doesn't document such an entity. But neither do deep-divergence studies. Instead, these studies assume the existence of such ancestors, and then merely attempt, given that assumption, to determine how long ago such ancestors might have lived." (page 111)
The concept of "common descent" is so entrenched in evolutionary thought that its advocates find themselves unable to distinguish between theory and evidence. For them, there is no argument - the case for common descent is overwhelming. To address this issue in greater depth, Meyer analyses "The animal tree of life" in Chapter 6. He critiques the way the concept is handled and shows that "common descent" is a dogma imposed on the evidence. The published animal trees all show common descent, but this is "because they all presuppose it, not because they demonstrate it." As an example of the mental block exhibited by evolutionists, consider the case of Larry Moran in his blog: "Darwin's Doubt: The Genes Tell the Story?" (Sandwalk, 6 September 2013). Moran writes as follows:
"There is strong evidence from molecular evolution that the major animal phyla share common ancestors and that these common ancestors predate the Cambrian by millions of years. In other words, there's a "long fuse" of evolution leading up to the Cambrian Explosion. Meyer refers to this as the "deep-divergence" assumption.
There are many versions of these trees. The one shown here is from Erwin et al. (2011). It's the one shown in the book The Cambrian Explosion by Douglas Erwin and James Valentine. It isn't necessarily correct in all details but that's not the point.
The point is that molecular phylogenies demonstrate conclusively that the major groups of animals share common ancestors AND that the overall pattern does not conform to a massive radiation around 530 million years ago."
The last sentence is an example of the conceptual problem identified by Meyer: the illustration used by Moran in his blog does not demonstrate anything conclusively! The Precambrian tree structure is entirely derived from the assumptions adopted by the researchers. Incidentally, Erwin et al. (2011) is referenced on page 461 of Darwin's Doubt, and cited on page 104.
The last chapter of Part 1 is devoted to the theory of Punctuated Equilibrium, whose architects were Stephen Jay Gould and Niles Eldredge. Whilst their orientation as palaeontologists allowed them to recognise that stasis is data and that abrupt appearance in the fossil record is ubiquitous, they did not succeed in explaining the Cambrian Explosion (which does not show small-scale diversity preceding large-scale disparity). Nor did they explain the abrupt appearance of complexity - finding themselves appealing to Darwinian mechanisms for building intricate structures. The problem of developing a coherent evolutionary theory that explained the data of the Cambrian Explosion remains.
Meyer summarises Part 1 in this way:
"To this point I've examined one main aspect of the mystery surrounding the Cambrian Explosion: the mystery of the missing Precambrian ancestral forms expected on the basis of Darwin's theory. The next group of chapters will examine a second, and perhaps more profound, aspect of the Cambrian mystery: that of the cause of the Cambrian explosion. By what means or process or mechanism could something as complex as a trilobite have arisen? Could natural selection have accomplished such a feat? To answer this question we will have to look more closely at what it takes to build a new form of animal life. And we'll see that an important part of the answer to that question will have to do with the concept of information." (page 155)
To be continued.
Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design
by Stephen C. Meyer
HarperOne (HarperCollins), New York, 2013. 520 pp. ISBN 9780062071477.
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