My post last week elicited a number of sharply critical comments from conventional evolutionary thinkers, most notably from my University of Chicago colleague Jerry Coyne on his Why Evolution Is True website. Let me respond and add four additional points.
1. The comments from Jerry Coyne and other orthodox critics on his website showed that they misunderstood my point completely. Apparently, all they could see was an assault on natural selection as a valid concept. Consequently, they confused the fixation of novel hereditary features, where selection plays an important role, with the origination of novel features, where selection does not (indeed, by definition, cannot) play a role. This distinction was pointed out most clearly on the blog by Victoria Alexander. My argument remains that the innovative process in evolution is rapid natural genetic engineering rather than gradual selection of small changes over long periods of time. This argument does not deny a role for selection. I simply assert that it is unrealistic to ascribe a creative (virtually deus ex machina) role to natural selection.
2. In his 2006 book on computational evolution, Compositional Evolution: The Impact of Sex, Symbiosis, and Modularity on the Gradualist Framework of Evolution, Richard Watson points out limitations of Darwinian-style hill climbing by successive accretion of small changes. This "accretionist" process is not well-suited to solving complex problems in silico. A superior computer evolution method is what Watson calls a "symbiogenetic" approach. In symbiotic evolution in silico, different parts of the problem are solved separately, and solutions are then combined symbiotically to generate novel combinations that could not evolve by accretion. This process has intriguing parallels with protein evolution by exon shuffling. Watson's work is also available online in his 2002 thesis.
3. I neglected to make it clear that Alfred Russell Wallace often viewed natural selection as a purifying and stabilizing force, not a creative one. In his seminal 1858 paper, "On the Tendency of Varieties to Depart Indefinitely from the Original Type," he wrote:
The action of this principle is exactly like that of the centrifugal governor of the steam engine, which checks and corrects any irregularities almost before they become evident; and in like manner no unbalanced deficiency in the animal kingdom can ever reach any conspicuous magnitude, because it would make itself felt at the very first step, by rendering existence difficult and extinction almost sure soon to follow.
The idea of selection as a feedback governor inspired Gregory Bateson to call Wallace the first cybernetician.
4. Other contemporary geneticists and evolutionists have taken a similar view to mine about the molecular origins of evolutionary novelties. An extensive and periodically updated bibliography on this subject can be found here . Some pertinent references include:
- Haig H. Kazazian. 2011. Mobile DNA: Finding Treasure in Junk (FT Press Science).
- Eugene Koonin. 2011. The Logic of Chance: The Nature and Origin of Biological Evolution (FT Press Science).
- Wagner A. The molecular origins of evolutionary innovations. Trends Genet. 2011 Oct;27(10):397-410.
- Werren JH. Selfish genetic elements, genetic conflict, and evolutionary innovation. Proc Natl Acad Sci U S A. 2011 Jun 28;108 Suppl 2:10863-70.
- Kaessmann H. Origins, evolution, and phenotypic impact of new genes. Genome Res. 2010 Oct;20(10):1313-26.
- Schaack S, Gilbert C, Feschotte C. Promiscuous DNA: horizontal transfer of transposable elements and why it matters for eukaryotic evolution. Trends Ecol Evol. 2010 Sep;25(9):537-46.
- Kazazian HH Jr. Mobile elements: drivers of genome evolution. Science. 2004 Mar 12;303(5664):1626-32.
- Miller WJ, Capy P. Mobile genetic elements as natural tools for genome evolution. Methods Mol Biol. 2004;260:1-20.