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Sunday, June 20, 2010

PZ's Radical Tree of Life

Check out PZ Myer's "radical" tree of life [Radial tree of life].

Why is this tree "radical"1? Because it completely misrepresents the relative importance of animals. Bacteria are relegated to insignificant status when, in fact, the diversity among bacteria is every bit as great as the diversity within eukarotes. Protists are grossly underrepresented as well.

This is a tree for those people who think that humans and other animals should be much more important than they are. One word for that is "radical" but I can think of many others. I'm surprised at PZ for using this tree. That's not at all like him.

1. PZ says it's a "radial" tree, not a "radical" tree.

[Tree Source: David M. Hillis, Derrick Zwickl, and Robin Gutell, University of Texas]


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  2. It seems likely, to me at least, that the radical in the label Radical Tree of Life is related to this:
    "The number of species represented is approximately the square-root of the number of species thought to exist on Earth"

  3. @Carl,

    I like the one from Jonathan Eisen except for the fact that it emphasizes the Three Domain Hypothesis. Personally, I don't think Archaea should be elevated to domain status and I don't think that Archaea and Eukaryotes share a common ancestor that evolved later than other prokaryotes.

    It does put the animals in their proper place, however and for that reason it's much better than PZ's.

  4. The radial (not radical) tree from the Hillis lab (not original to PZ as he makes clear) has the virtue of presenting extant species as being equally evolved-- there is no implication of 'higher' or 'lower' life forms. The Eisen tree implicitly perpetuates that misconception by placing eukaryotic branches at the top. I agree entirely with Larry that the Hillis tree gives grievously short shrift to the diversity of microbial species relative to that of macroscopic lineages.

  5. Well,

    What about we make a mess of this entry and start by asking how much horizontal gene transfer messes the tree up. Then talk about the 1% tree of life by Bork, then go to Ford Doolittle and, perhaps, Gogarten, to refute that a tree is possible, visit Koonin's forest of life that, in some respect, seemed to give hope to "tree huggers so to speak" (as Koonin put it), and then we note that we might not be able to reach a conclusion, or maybe not even agree on many thing, except that no tree should give humans much more importance than deserved.


  6. The Eisen tree is better, although I would quibble with the representation of Excavates on the Eukaryotic side of things.

    As for the three domain hypothesis, I mostly agree with you Larry, although deciding exactly what to draw instead if a little problematic. I do personally lean towards the Eukaryotes emerging from within the Archea myself, making Archea a non-monophyletic group.

  7. In my defense, I specifically explained that it was a tree biased to overrepresent animals.

    I used it to make two points: that we're all related, and that all extant species are equally "evolved" -- the circularity is nice because it makes it easier to make the point that no one species is at the head of the table.

  8. iTOL, the Interactive Tree of Life, might be more to your taste. I came across it while looking for a good way to display my Flickr tree of life.