Tuesday, December 27, 2005

A neo-neo-Darwinian Synthesis?   posted by Razib @ 12/27/2005 01:53:00 PM

Mike Lynch has a new sweeping paper titled The Origins of Eukaryotic Gene Structure over at Molecular Biology and Evolution. In it he attempts to marry population genetic theory with a broad evolutionary view of genomic architecture. I won't really attempt to summarize Lynch's paper, but if you have a biological background I highly recommend it. For those of you who aren't as fluent in the language of biology the last 2/3 of the paper which focuses on molecular genetics might seem a bit of an alphabet soup (TATA, UTR, mRNA, etc.). But I don't think the material is fundamentally difficult, and I believe that attempting to digest the details of genuine evolutionary biology which grapples with the microevolutionary dynamics that lay at the root of macroevolutionary diversity can impart to one a better sense of what the science of evolution is all about. For those without access I have uploaded the file as "lynch2005" in the gnxp forum. Don't be daunted when the Adobe tells you that it is "38 pages," as only 18 of them are text (the rest being citations and figures). I will quote a portion of the conclusion though that communicates the thrust of his argument:

Because evolution is a population-level process, any theory for the origins of the genetic machinery must ultimately be consistent with basic population-genetic mechanisms. However, because natural selection is just one of several forces contributing to the evolutionary process, an uncritical reliance on adaptive Darwinian mechanisms to explain all aspects of organismal diversity is not greatly different than invoking an intelligent designer.

This paper represents a first step towards the formal development of the general theory for the evolution of the gene that incorporates the universal properties of random genetic drift and mutation pressure...A significant area of future research will be take these observations on gene and genome complexity to the next level, to evaluate whether natural selection is a necessary and/or sufficient force to explain the evolution of the celluar and developmental complexities of eukaryotes

A few points on this conclusion. Molecular Biology and Evolution is not a popular press publication, so Lynch's jab at adaptationists is not meant to give comfort to Intelligent Design. Rather, much of his work over the past few decades has been to emphasize that random genetic drift is a very powerful force. The mutational meltdown theory is a case in point. It is interesting to me that Lynch is echoing some of the sentiments expressed in Why Men Don't Ask for Directions, making an analogy between strong adaptationism and Intelligent Design (The Blind Watchmaker is a lucid and accessible exposition of the adaptationist paradigm). I think the important point about Lynch's paper is tha it is reflective of the same mentality which suffuses Armand Leroi's The scale independence of evolution, that macroevolution and microevolution are operational categories which exist for sake of verbal convenience, not fundamentally distinct processes. In discussions with many lay persons who have some familiarity with the "evolution controversies" we almost always stumble over the problem that I do not assume anything of the kind, and I need to go back to ground zero and rework their perception of the models which are genuinely assumed in evolutionary biology. Even if an individual does not subscribe to a Creationist or Intelligent Design theory, they usually accept the terminology, distinctions and arguments put forward by Creationists and ID theorists as coherent and relevant. In reality these talking points emerge out of a parallel intellectual and theoretical culture from that of mainstream evolutionary biology, which, unfortunately, is much more intuitively comprehensible (see my argument in Endless forms most continuous?). In any case, though Intelligent Design proponents argue that evolution is on its last legs it seems to me that the rise of the post-genomic era, bioinformatics and evo-devo all point to a future where evolutionary biology becomes even more robust, with tendrils of consiliated unity arising from the common substrate of molecular biology and the formal language of population genetics.