The September/October issue of Books & Culture has a review by CSC senior fellow Jonathan Wells of The Plausibility of Life by Marc W. Kirschner and John C. Gerhart, two eminent biologists. The book has been acclaimed since its arrival earlier this year for providing answers for the last remaining “gap” in Darwin’s theory of evolution. Wells –an eminent biologist himself– is, not surprsingly, skeptical of the claim. (He knows a thing or two about the gaps in Darwin’s theory.)
To overcome the weakness in existing evolutionary theory, Kirschner and Gerhart propose what they call “a major new scientific theory: facilitated variation.” The authors note that organisms consist of “core processes” that have apparently been “conserved” since their evolution from a common ancestor. The most basic of these are found in all living organisms from bacteria to humans; for example, dna replication, protein synthesis, and metabolic pathways. Kirschner and Gerhart acknowledge that they have no explanation for the origin of these in the first living cell. “Evidence is completely lacking about what preceded this early cellular ancestor,” they write. “Everything about evolution before the bacteria-like life forms is sheer conjecture.”
There are other major transitions in the history of life that Kirschner and Gerhart also concede remain unexplained. One of these was the “invention” of the first eukaryotes, cells with nuclei that are very different from bacteria. “Generating the first eukaryotic cell was a major and enduring accomplishment,” they write. “Extensive innovation showed up in the complexity and organization of the eukaryotic ancestor.” Another major transition was the origin of multicellular organisms, which require complex mechanisms for cells to aggregate and communicate with each other. Still another unexplained transition was the origin of animal body plans in the Cambrian explosion. “Once again,” write Kirschner and Gerhart, “a new suite of cellular and multicellular functions emerged rather quickly and was conserved to the present.”
Some other major transitions that Kirschner and Gerhart concede remain unexplained are the origin of limbs in the first land vertebrates, the origin of neural crest cells that sculpt the heads and nervous systems of vertebrates, and the origin of the neocortex in vertebrate brains. “The origin of these processes and properties would seem to be the primary events of evolution, requiring high novelty,” but the authors admit they cannot explain them. So, what does their theory explain?
According to Wells, Kirschner and Gerhart are basically just speculating. They don’t have much evidence to backup their speculations.
Where, then, is the evidence that “facilitated variations” can produce heritable changes that lead to evolutionary novelty? Kirschner and Gerhart write:
“At some point, such heritable regulatory changes will be created in a test animal in the laboratory, generating a trait intentionally drawing on various conserved processes. At that point, doubters would have to admit that if humans can generate [such] variation in the laboratory in a manner consistent with known evolutionary changes, perhaps it is plausible that facilitated variation has generated change in nature. Such experiments are just now becoming feasible.”
What does Wells think of all this?
In my book Icons of Evolution, I pointed out that using structural similarity (“homology”) as evidence for Darwinian evolution is problematic. Without an unguided natural mechanism, it is impossible to establish that similarities are due to common ancestry rather than common design. Kirschner and Gerhart argue that their theory solves the problem. Maybe. Maybe not. It would help if they could provide good evidence for their theory, but the best they can do is promise us that such evidence will be forthcoming. In the meantime, they expect us to believe that “the modern molecular evidence for homology, its development, and its evolution, is unassailable.”
So what are we to make of The Plausibility of Life? Its authors claim to complete Darwin’s theory by closing its last remaining major gap, yet they concede that the completed theory has no explanation for the origin of core processes in the first cells, the first eukaryotes, the first multicellular organisms, animal body plans, or vertebrate limbs, heads and brains. There seem to be more gaps in evolutionary theory now than there were before Kirschner and Gerhart got started.
The book also contains attacks on ID proponents, specifically Michael Behe, for which Wells takes the authors to task.
The authors mention only one id proponent by name in the main text of their book: Michael Behe. They write: “Behe uses elaborate biochemical examples to intimidate us into believing that the complexity of living cells is beyond understanding.” But this misrepresents Behe’s position, which is that complexity is understandable–as the result of intelligent design.
The review is worth reading, as is, I’m sure, the book itself.