About Rationally Speaking
Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.
Tuesday, February 17, 2009
Jerry Coyne and the Extended evolutionary Synthesis
Jerry praises Zimmer’s overall essay on Darwin in Time magazine, but he adds that his enjoyment was spoiled because “Zimmer seems to buy into something he calls the ‘extended evolutionary synthesis.’” I think Coyne is being a bit disingenuous here, writing as if he had never heard before of an extended synthesis and attributing the term to Zimmer. But he goes on to say: “It seems to me that a science journalist should do more than simply tell their readers that something new is in the air: a journalist should EVALUATE these new claims. If all one did was say ‘some evolutionists think ...’ and then describe their thoughts, any old claim could get press.”
Right, and I have amply criticized “journalists” who not only uncritically report competing claims but even make up stuff out of their fertile imaginations, like Suzan Mazur has most outrageously done with her inane “Scoop” series. However, talk of an Extended Synthesis isn’t “any old claim,” it is a serious discussion among credentialed scientists. Coyne, of course, most certainly has the right to disagree with his colleagues, but that doesn’t mean that the topic is not a respectable object of coverage by a professional journalist. (It is true that another skeptic of the necessity of updating the Modern Synthesis, Indiana University’s Michael Lynch, has actually compared -- in print in the prestigious Proceedings of the National Academy of Sciences -- proponents of some new ideas in evolutionary biology to supporters of intelligent design creationism, but I think Jerry Coyne both knows better and has more style in his writings.)
Jerry rightly says that “It just isn’t true to say that every aspect of the Modern Synthesis is fiercely debated,” a claim he attributes to Zimmer in the Time article. Except that Zimmer was clearly writing about the extended synthesis claims, which are, in fact being fiercely debated, as Coyne’s own writings surely attest. At any rate, as Ryan Gregory (over at Genomicron) correctly states in his commentary on Coyne’s piece, “The point is that many people feel that we need to have a conversation about how well the Modern Synthesis covers [a variety of] phenomena, adding that “An extended synthesis would not involve an overthrow of current theory (hence, "extended").”
Coyne then brings up the poor old ghost of Richard Goldschmidt, the geneticist who famously criticized the Modern Synthesis while it was happening, in the 1940s. Goldschmidt, as it turns out, was wrong in his proposed solution to the problem (“hopeful monsters” and such), but he had identified a problem -- the incompleteness of the synthesis in terms of developmental biology and macroevolution -- that has characterized, on and off, evolutionary biology’s discourse ever since.
Jerry’s post continues with a list of issues he thinks are overblown: he says that nobody claimed that natural selection can completely explain species diversity (true, but my original point was that some macroevolutionary patterns are difficult to account for by simple micro-evolutionary extrapolation, as demonstrated in a series of papers by David Jablonski, also at the University of Chicago); he states that gene swapping isn’t important, especially in vertebrates (nobody claimed it is, in that group, but people are seriously reconsidering the whole idea of a “tree of life” as a result of what appears to be extensive gene swapping among today’s non-eukaryotes and early on in the history of life); and he asserts that nobody suggested that gene networks get rewired by any means other than natural selection (actually, Lynch himself has argued that a lot of genomic-level changes are not due to selection, and at any rate my original point was that network-level properties are making simple population genetic models increasingly inadequate as a full description of evolutionary change).
Jerry is “irritated” by what he calls “BIS–the Big Idea Syndrome,” where any new idea that comes about, be it modularity, evolvability, evolutionary capacitors, epigenetic inheritance, phenotypic plasticity, genetic accommodation, species selection, cis-regulatory evolution, and so on and so forth, “becomes the centerpiece of a claim that modern evolutionary theory is ripe for a revolution.” Again, nobody I know is calling for a revolution, but the above mentioned ideas and empirical evidence cannot simply be filed away as “more of the same.” Gregory’s post referred to above lists 16 new, broad empirical findings that occurred after the formulation of the Modern Synthesis, a very partial list indeed. Are these all simply variations on a theme established at the onset of the 20th century? At some point Coyne, Lynch and others need to do a bit more than just shak their heads and play armchair curmudgeon (Jerry’s word). They need to address the hundreds of papers and dozen or more books, written by a good number of respected colleagues, that have detailed why the Modern Synthesis needs updating and what this update is beginning to look like.
None of this, of course should give any comfort to creationists and their ilk (though I can’t wait to see the inane posts that will surely result from this exchange between Jerry and me!), because incompleteness and tentativeness are inherent features of scientific theories in all branches of science. Physicists have been discussing how to reconcile relativity and quantum mechanics for decades, and they still don’t know what their next standard model will look like. This doesn’t mean that physics is dead; on the contrary, it is a tribute to the vitality of the scientific enterprise and to the people who passionately devote themselves to it. Jerry and I are probably wrong on some of the details of what we are saying. Time will probably show that he is much too conservative and I am much too liberal about what is needed in evolutionary theory and where it’s going to come from. But it is precisely this continuous dialectic within the scientific community that makes for eventual progress. Welcome to the excitement of science!
A brief (and certainly incomplete) guide to the literature advocating an extended evolutionary synthesis and/or making specific proposals for it:
Carroll SB (2008) EvoDevo and an Expanding Evolutionary Synthesis: a genetic theory of morphological evolution. Cell 134: 25-36.
Colegrave N and Collins S (2008) Experimental evolution and evolvability. Heredity 100: 464-470.
Gould SJ (2002) The Structure of Evolutionary Theory. Cambridge MA, Harvard University Press.
Hansen TF (2006) The evolution of genetic architecture. Annual Review of Ecology and Systematics 37: 123-157.
Hendrikse JLT, Parsons E and Hallgrimsson B (2007). Evolvability as the proper focus of evolutionary developmental biology. Evolution & Development 9(4): 393-401.
Jablonka E, Lamb MJ (1995) Epigenetic Inheritance and Evolution. Oxford: Oxford University Press.
Kirschner M, Gerhart J (2005) The plausibility of life: resolving Darwin's dilemma. New Haven: Yale University Press.
Kutschera U, Niklas KJ (2004) The modern theory of biological evolution: an expanded synthesis. Naturwissenschaften 91:255 – 276.
Love AC (2006) Evolutionary morphology and EvoDevo: hierarchy and novelty. Theory in Biosciences 124: 317-333.
Müller GB (2007) EvoDevo: extending the evolutionary synthesis. Nature Reviews Genetics 8: 943-949.
Müller GB, Newman SA eds. (2003) Origination of Organismal Form. Cambridge MA: MIT Press.
Odling-Smee FJ, Laland KN and Feldman MW (2003) Comments on Niche Construction: The Neglected Process in Evolution. Princeton, Princeton University Press.
Pigliucci M (2007) Do we need an extended evolutionary synthesis? Evolution 61(12): 2743-2749.
Pigliucci M (2008) Is evolvability evolvable? Nature Reviews Genetics 9: 75-82.
Robert JS (2004) Embryology, Epigenesis, and Evolution: Taking Development Seriously. Cambridge, England, Cambridge University Press.
Rose MR, Oakley TH (2007) The new biology: Beyond the Modern Synthesis. Biol Direct 2:30.
Sansom R, Brandon RN eds. (2007) Integrating Evolution and Development: From theory to practice. Cambridge: MIT Press.
Wagner A (2005) Robustness and Evolvability in Living Systems. Princeton, NJ, Princeton University Press.
Wagner GP and Altenberg L (1996) Complex adaptations and the evolution of evolvability. Evolution 50: 967-976.
West-Eberhard MJ (2003) Developmental Plasticity and Evolution. Oxford, England, Oxford University Press.