Book Review: Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design
Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design is the new book by Stephen Meyer of the Discovery Institute. The book's title is taken from Charles' Darwin's concern that his theory could not explain the lack of potential ancestors of animals appearing prior to what has been called the Cambrian explosion. During this brief period of time (~10 million years), numerous phyla (the highest classification scheme below "kingdom") of complex animals with novel body plans suddenly appeared from nowhere. Although additional classes of animals appeared subsequent to the Cambrian explosion, all animal phyla (both extant and extinct) originated at that time. So, is the Cambrian explosion still a problem for neo-Darwinian evolution?
Charles Darwin and most scientists who believe in the neo-Darwinian theory of biological evolution expect that the fossil record should show gradual evolutionary diversity at the species and genus level followed by the evolution of new biological families, orders, classes, and then phyla. However, the Cambrian explosion turns that idea on its head, with a rapid evolution of phyla followed by diversification of new orders, family, and species. In other words, the big leaps in organism design came before speciation, which is completely contrary to what gradualism would predict.
Attempts to discredit the Cambrian fossils
Several different attempts were made by evolutionists to discredit the problem posed by Cambrian explosion fossils. Even early on, Darwinists attempted to classify radically different animals into existing phyla in an attempt to minimize the obvious the diversity of the fossil evidence. Later efforts hypothesized that pre-Cambrian fossils just hadn't been found yet or that the soft-bodied ancestors of the Cambrian fauna just hadn't fossilized. All these attempts to minimize explosive nature of the Cambrian fossil evidence were shown to be false, since exquisitely-preserved soft-bodied animals, including sponge embryos showing cell nuclei, were shown to be preserved in Cambrian sedimentary rock.
Still other Darwinists have cited the appearance of fossils in the Ediacaran period, immediately prior to the Cambrian. These fossils represent a radical leap from previous life on earth, which was purely single-celled organisms. However, the phyla represented could account for, at most, only four of the twenty phyla that appeared during the Cambrian explosion. In addition, these organisms lack the innovative designs of the Cambrian, such as eyes, heads, mouths, guts, and spinal cords.
Based upon the concept of a molecular clock in the genetic sequences of key genes of Cambrian ancestors, scientists have attempted to calculate the time at which these hypothetical ancestors must have evolved. Since the fossil record failed to demonstrate these pre-Cambrian ancestors, scientists had hoped to raise doubt on the brevity of the Cambrian explosion. Calculations based upon a molecular clock showed that these hypothetical ancestors must have arisen a billion or more years ago (half a billion before the Cambrian explosion). However, there isn't even a hint of multicellularity that far back, even though we can find fossil evidence of single-celled organisms as far back as 3.5 billion years ago. Molecular clocks based upon different proteins in different studies produce divergence dates that vary by more than 1 billion years. Hence, the accuracy of such studies must be questioned.
Darwin's Doubt contains a number of chapters dedicated to the question of how new information and new genes can arise, which might explain the mechanism behind the Cambrian explosion. The problem is not as simple as it might seem at first, since not only were new body plans developed, but dozens of new kinds of organs, tissues and cell types for all those body plans. Such massive innovations require the addition of thousands of new genes that are perfectly integrated with each other in order to produce an organism that functions. The Darwinian explanations for the origin of genetic information would be hard-pressed to explain how all those new designs appeared. Although the chapters in "How to build an animal" tend to be thorough, I would have preferred to see a better rebuttal to the primary Darwinian mechanism cited for the appearance of new genes—exon shuffling.
Scientists have learned a lot by studying fruit flies. The use of mutation-causing chemicals during development have demonstrated what genes are important during the development of fruit fly larva. However, virtually all the mutations that affect embryogenesis produce fruit flies that are either non-viable or severely compromised. Better adapted fruit flies are never produced. So, there is a question as to how mutation can ever select a better adapted individual. Since macroevolution is dependent upon mutations that change the body plans of species, mutations that do so must impact development early in the process. However, these kinds of mutations are almost always deleterious.
Meyers goes on to examine alternative theories to neo-Darwinism, such as developmental gene regulatory networks, self organization, large-scale mutations, evo-devo models, mutations of cis-regulatory regions or homeobox genes, neutral or non-adaptive evolution and epigenetic inheritance. Darwin's Doubt ends with chapters on evidence for intelligent design, how science operates, and why it matters.
Darwin's Doubt is a really good, comprehensive examination of the Cambrian explosion and its implication regarding the neo-Darwinian model of evolution. As in Meyer's Signature in the Cell, the book is heavily referenced for those who want to explore topics more thoroughly. Darwin's Doubt tends to be somewhat more technically challenging, but not beyond the ability of the average science enthusiast to understand. One of the strengths of the book is that it thoroughly covers the numerous naturalistic models that attempt to explain the origin of new biological information. It has been a great help to me in helping to elucidate the numerous naturalistic models proposed to explain the diversity of life and the fossil record.
Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design (Paperback)
by Stephen C. Meyer
Date published: June 18, 2013
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Last Modified July 26, 2013