November 14, 2005 | David F. Coppedge

Like, Make a Tree

Three Darwinist professors lamented recently in Science1 that few scientists are making like a tree: “‘tree thinking’ remains widely practiced only by professional evolutionary biologists,” they said.  And just what is “tree thinking”?  It is basically thinking like Darwin; i.e., looking at the living world with phylogenetic glasses:

The central claim of the theory of evolution as laid out in 1859 by Charles Darwin in The Origin of Species is that living species, despite their diversity in form and way of life, are the products of descent (with modification) from common ancestors.  To communicate this idea, Darwin developed the metaphor of the ‘tree of life.’  In this comparison, living species trace backward in time to common ancestors in the same way that separate twigs on a tree trace back to the same major branches.   (Emphasis added in all quotes.)

What prompted this editorial?  “This is a particular cause for concern at a time when the teaching of evolution is being challenged,” they say.  But there’s a positive side, too: “because evolutionary trees serve not only as tools for biological researchers across disciplines but also as the main framework within which evidence for evolution is evaluated.
    While tree-thinking is useful for everyone, the art of generating trees is best left to the wizards:

At the outset, it is important to clarify that tree thinking does not necessarily entail knowing how phylogenies are inferred by practicing systematists.  Anyone who has looked into phylogenetics from outside the field of evolutionary biology knows that it is complex and rapidly changing, replete with a dense statistical literature, impassioned philosophical debates, and an abundance of highly technical computer programs.  Fortunately, one can interpret trees and use them for organizing knowledge of biodiversity without knowing the details of phylogenetic inference.  The reverse is, however, not true.  One cannot really understand phylogenetics if one is not clear what an evolutionary tree is.

They provide some examples of potential sources of confusion.  “Although closely related species tend to be similar to one another, this is not necessarily the case if the rate of evolution is not uniform:” for instance.  “Crocodiles are more closely related to birds than they are to lizards, even though crocodiles are indisputably more similar in external appearance to lizards.”
    A statement like that would surely shock a novice.  It’s not the outward similarity, they explain, but the phylogenetic inference that counts.  Evolutionary history is not progressive, nor is it uniform.  In addition, we see only the tips of the branches inhabited by living or fossil organisms; occupants of the nodes (common ancestors of the branches) are only inferred, and may not have looked like anything alive today.  “Thus, for all its importance,” they caution, “tree thinking is fraught with challenges.
    But then how can anything fraught with challenges be important or useful?  Let’s revisit their motives for proposing that tree-thinking should extend beyond the cloisters of evolutionary systematics.  Here’s the bottom line:

Tree thinking belongs alongside natural selection as a major theme in evolution training.  Further, trees could be used throughout biological training as an efficient way to present information on the distribution of traits among species.  To this end, what is needed are more resources: computer programs, educational strategies, and accessible presentations of current phylogenetic knowledge.
    Phylogenetic trees are the most direct representation of the principle of common ancestry–the very core of evolutionary theory–and thus they must find a more prominent place in the general public’s understanding of evolution.  As philosopher of science Robert O’Hara stated, “just as beginning students in geography need to be taught how to read maps, so beginning students in biology should be taught how to read trees and to understand what trees communicate.”  Among other benefits, as the concept of tree thinking becomes better understood by those in the sciences, we can hope that a wider segment of society will come to appreciate the overwhelming evidence for common ancestry and the scientific rigor of evolutionary biology.

1David A. Baum, Stacey DeWitt Smith, Samuel S. S. Donovan, ”Evolution: The Tree-Thinking Challenge,” Science, Vol 310, Issue 5750, 979-980 , 11 November 2005, [DOI: 10.1126/science.1117727].

This article is very revealing.  The best way to understand it is to imagine oneself in ancient Babylonia, listening to some wizards of hepatoscopy (divination by reading the liver) lamenting the paucity of awareness of their craft among the astrologers and the general public.  They make a pitch in the Chaldean Journal about how useful hepatoscopy is to the general science of divination.  While admitting that their charts and diagrams are difficult to devise, they nevertheless argue that the charts are useful representations of fundamental insights, and took an awful lot of hard work to produce.  Their recommendation is to print more copies of their liver diagrams and instruct the young in the basic concepts of interpreting livers until the concept of liver-thinking becomes better understood and appreciated.
    Far off?  Not by much.  Look what they admitted: phylogenetic inference from the actual data of biodiversity is “fraught with challenges.”  The field is “complex and rapidly changing.”  It has its own “dense statistical literature” impenetrable to those “outsiders” of the art.  It is an arena of “impassioned philosophical debates.”  One can imagine Babylonian hepatomancers in similar circumstances, adjusting their charts each time the king loses a battle despite their prognostication.  No problem; it’s all part of the “scientific rigor” of The Craft.
    Notice also that tree-thinking is an a priori stance one takes before looking at the data.  It’s a world view: “the main framework within which evidence for evolution is evaluated.”  But what is being evaluated: the evidence, or the framework?  Since everything must fit into The Framework from the outset, no amount of change, debate, challenge or complexity endangers The Framework.  It is the grid through which all data must be sifted, the colored glass through which all wavelengths must be filtered.  This is very different from a geographical map with which they compare it (see analogy in the Baloney Detector).  A map represents visible data that can be corroborated in the present; a phylogenetic tree infers relationships in the unobservable past.  We do not conform the data to the map, but the other way around.  Not so with the Darwin Tree of Life.  Evidence is really secondary, because The Framework is already established.  Branches may shift here or there, but The Tree, as Platonic form, remains sacrosanct.  (You’ll notice that these wizards only bluffed about the “overwhelming evidence” for common ancestry and the “scientific rigor” of evolutionary biology; see 08/11/2003 and 06/13/2003 entries).
    Rightly did Jonathan Wells classify Darwin’s tree of life as an Icon of Evolution.  An icon is a symbol, a representation of an article of faith.  The early icons of Jesus were not evidence for his divinity; they were reminders and representations of what the faithful already believed about him.  Proof of his divinity came not from the icons, but from the historical facts and eyewitness accounts of his miracles and resurrection.  As such, “icon-thinking” and meditation on the artistic representations would have constituted a weak apologetic.  The iconoclasts of early Christendom did not deny the object of the icons, but argued that the icons became idols, mere graven images that distracted one’s attention from the real person of Jesus Christ.  How much more an icon based on false premises and absent evidence will mislead a scientist and obscure honest investigation.  Like the icons of pagan gods adorning ancient temples, it substitutes a fantasy for the real world.
    These three Darwin Party soothsayers want to short-circuit the proof from evidence and train novitiates by having them meditate on the icons.  They want computer programs, educational strategies and accessible representations of the products of their divination; they want to say, “believe, then interpret.”  They want to push this Framework, this faith – indeed, this religion – in the schools, to raise a new crop of devotees and practitioners of The Craft.  Such flagrant advocacy built on such shallow premises deserves a response in kind, from an iconoclast on that level.  We quote the noted philosopher Biff: “Make like a tree, and get outta here.”

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