Facing Facts

Yesterday I offered readers a link to a video of a thought-provoking conversation (transcript here, video here) between J. Craig Venter and Richard Dawkins (if you haven’t found the time to look at it yet, I do hope you will). In the ensuing thread, however, rather than discussing any of the forward-looking topics that had come up, our commenters focused exclusively on the various ways that people found Dawkins annoying or disappointing, and I piled on as well.

Yes, he can be a bit of a pill. But in that video, I saw something that shouldn’t go unremarked.

In the course of the conversation, the topic turned to molecular taxonomy: the working out of ancestral relations among species by the study of the divergence of their genomes. This is an important tool, and one that Dawkins has devoted a great deal of his time to the study of; the particulars of the tree of life depicted in his outstanding book The Ancestor’s Tale depend heavily on this analytical technique.

During the course of the onstage discussion, Venter mentions to Dawkins that in the course of his work he has come to realize that a great deal of genetic material has been exchanged between species, over geological time, by the action of viruses. Dawkins is quick to realize that this might be something of a bombshell as far as the reliability of molecular taxonomy is concerned, and presses Venter on the point. There are plainly technical details to examine further, but Venter seem to think that this is indeed a relevant concern.

Dawkins, having immediately grasped the implications of this suggestion for a field in which he has worked for his entire career, is quite plainly startled; it may well mean that much of what he has considered to be solidly established taxonomy will have to be re-examined. But he knows that Venter is arguably in a better position than any one alive to much such a claim, and that if he is indeed doing so, then it must be taken seriously, no matter what the implications.

And here is the point: Dawkins, obviously shocked, makes clear nevertheless that while he will need some convincing, he is open to changing his mind. He is willing, in that moment, and on that public stage, to be shown that much of his hard-won understanding of the branching tree of life might in fact be wrong.

I understand that the man rubs a lot of people the wrong way, but this deserves our respect. Dawkins gets a lot of heat for his sustained assault upon religion, but here he exemplifies what is right about science.

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  1. bob koepp says

    Absolutely! When it comes to questions internal to science, Dawkins “gets it.”

    Posted February 9, 2008 at 3:25 am | Permalink
  2. Andrew says

    I know this is a bit tangential to the point of your post, and I have not had a chance to watch the exchange but I am surprised that the idea of viral mediated lateral gene transfer caught Dawkins by surprise. Knowledge of this process is not new. And Venter is far from alone in understanding this. His group did publish this recent paper but they were beaten to the viral sequence abundance observations by others (see here)

    From what I’ve seen I don’t think that this type of gene transfer is going to mess up the currently accepted molecular phylogenies. Evidence of it occurring with any regularity is currently limited to exchanges between a small number of closely related groups.

    Posted February 9, 2008 at 9:28 am | Permalink
  3. Malcolm says

    Hi Andrew,

    I was hoping you might weigh in on this one, and I don’t think your remarks are tangential at all. I was suprised also that Dawkins might be unaware of this effect, and his skepticism about the degree to which it might undermine molecular taxonomy seemed to focus on exactly the issues you raise (this is what I referred to his “needing some convincing”).

    I haven’t looked at your links yet, but I do hope that the foundation of our current taxonomic edifice isn’t weakened by this effect. Even if the lateral transmission is usually confined to related groups, I could imagine that it could diminish our confidence in the specifics of how the tree branches at small scales. For example, if common ancestor A gives rise to species B and C, and C has a mutation that it passes on to its descendants D and E, then should a virus transmit the gene to B’s descendant F, things might get confusing.

    I was talking about this with my father last night and he pointed out that in the vast majority of such cases the effect is not in germ-line cells, and so is not passed along to descendants.

    How about a post of your own on the subject?

    Posted February 9, 2008 at 1:23 pm | Permalink
  4. Andrew says

    Your fathers point is valid for multicellular organisms. We are not about to discover that humans are more closely related to dogs than monkeys. However, the vast majority of life is comprised of unicellular organisms. With these, there is no separate germ line, any alteration of the genome will be carried into subsequent generations.

    As far as this type of finding altering our current molecular taxonomies, I’d make two points:
    1- The actual relationships between many groups remain far from settled. This is due, in part, to methodological limitations (see for example the description by Dawkins in The Ancestor’s Tale of long branch attraction in phylogenetic trees).

    2- People working to determine relationships between closely related organisms are aware of lateral gene transfer and make every effort to remove the influence of such events. With the availability of entire genomes for many species, consensus trees based on multiple genes is one way to deal with the problem.

    I’d love to write a longer post or even a series of posts on this but with two young kids and a demanding job I have pretty much given up on finding the time to blog these days.

    Posted February 10, 2008 at 7:47 pm | Permalink