What do readers make of claims for neutral evolution?
|August 26, 2013||Posted by News under Darwinism, News|
As in Carl Zimmer’s recent Scientific American article here.
The scenario that Gray proposes for the evolution of RNA editing goes like this: an enzyme mutates so that it can latch onto RNA and change certain nucleotides. This enzyme does not harm the cell, nor does it help it—at least not at first. Doing no harm, it persists. Later a harmful mutation occurs in a gene. Fortunately, the cell already has the RNA-binding enzyme, which can compensate for this mutation by editing the RNA. It shields the cell from the harm of the mutation, allowing the mutation to get passed down to the next generation and spread throughout the population. The evolution of this RNA-editing enzyme and the mutation it fixed was not driven by natural selection, Gray argues. Instead this extra layer of complexity evolved on its own—“neutrally.” Then, once it became widespread, there was no way to get rid of it.
David Speijer, a biochemist at the University of Amsterdam, thinks that Gray and his colleagues have done biology a service with the idea of constructive neutral evolution, especially by challenging the notion that all complexity must be adaptive.But Speijer worries they may be pushing their argument too hard in some cases. On one hand, he thinks that the fungus pumps are a good example of constructive neutral evolution. “Everybody in their right mind would totally agree with it,” he says. In other cases, such as RNA editing, scientists should not, in his view, dismiss the possibility that natural selection was at work, even if the complexity seems useless.
Gray, McShea and Brandon acknowledge the important role of natural selection in the rise of the complexity that surrounds us, from the biochemistry that builds a feather to the photosynthetic factories inside the leaves of trees. Yet they hope their research will coax other biologists to think beyond natural selection and to see the possibility that random mutation can fuel the evolution of complexity on its own. “We don’t dismiss adaptation at all as part of that,” Gray says. “We just don’t think it explains everything.”
Uh, no. Thoughts?
Is this serious inquiry or the Emperor’s lapdogs at play?