Thursday, July 30, 2009

Perspectives on the Tree of Life: Ford Doolittle

 
As you read this I'll be in Halifax listening to Ford while he explains his version of the tree of life and why it conflicts with Darwinism. And why that shouldn't matter ...
The Tree of Life, from three sides now

My personal experiences in talking about the meaning of Lateral Gene Transfer (LGT) for the Tree of Life (TOL) teach me that people care about this otherwise seemingly hopelessly academic question for three reasons. It challenges their understandings of the history of our science, their often unexpressed philosophies of evolution and science, and their political stances vis-à-vis the struggle against ID creationism. I will review some of the science which has lead to the currently popular notion that what molecular phylogeny ultimately seeks is The Tree of Cells (TOC), a tracing back from the present of all speciation events, and before sex of all cell divisions, to some single ancestral cell. But because of LGT, this single cell cannot have been what most people want LUCA (the Last Universal Common Ancestor) to be – that is, a single cell (or species) whose genome contained the last common ancestral versions of all extant genes. In fact it need have contained none of these, and to equate the TOC with the TOL is a serious misreading of Darwin. Eric Bapteste and I have argued that the TOL was in fact an hypothesis about the relationship of evolutionary pattern (“natural classification”) to evolutionary process (specifically that it is tree-like), and that this hypothesis is false. Saying this causes problems to the brave defenders of evolution (such as Eugenie Scott and others at the NCSE) in the death-struggle against IDers. I will try to ameliorate the damage by suggesting that we evolutionists need to lighten up, stop defending “Darwinism” and admit that all we need to defend is this: Natural genetic, population genetic, ecological and environmental processes – that we for the most part already understand – operating over long periods of time, are necessary and sufficient to account for the diversity and adaptedness of life as we know it.


4 comments :

  1. Ford's philosophical bent is leading him too far from doing real science...

    ReplyDelete
  2. +1 what Rosie said...

    *must not go off on rant again. Really mustn't.

    So 'life' isn't really contained in cells anymore?

    ReplyDelete
  3. LUCA representing a single species/cell is not what I was taught nor what I hear knowledgeable people talk about even those who support the three domain hypothesis. They speak of ancestral community. Seems too much of a strawman.

    ReplyDelete
  4. Probably the worst part is the appeal to Darwin, we've come a long way since 1859 in evolutionary biology.

    The TOC concept is interesting, but as species are collections of individuals, it seems that there will be a high degree of coalescence between it and the TOL. Which, unless the TOC generates some useful insights, will probably leave it languishing in the background.

    And;
    "Eric Bapteste and I have argued that the TOL was in fact an hypothesis about the relationship of evolutionary pattern (“natural classification”) to evolutionary process (specifically that it is tree-like), and that this hypothesis is false."
    /facepalm @ the bolded bit, as the tree-like structure describes much of the majority of evolutionary histories. And while there is a merging of branches, in terms of endosymbiosis, hybridisation and HGT, this doesn't mean we need to throw out the basic TOL concept. Especially for one that doesn't seem to have all that much in the way of advantages over the TOL...

    ReplyDelete