Wednesday, January 07, 2004

Species, Language and Reality

You may have heard that the fossil record shows surprisingly little evidence of gradual transitions between species, which is the kind of evidence we should expect if the theory of evolution is to be believed. So then what's going on? Nothing, Richard Dawkins argues, in his book Climbing Mount Improbable, as the whole issue is actually a phantom created by language overshadowing reality.

From pages 95 and 96 of the first Penguin paperback edition of the book:

There is a supremely banal reason why transitional forms are generally lacking at the species level. I can explain it best with an analogy. Children turn gradually and continuously into adults but, for legal purposes, the age of majority is taken to be a particular birthday, often the eighteenth. It would therefore be possible to say, 'There are 55 million people in Britan but not a single one of them is intermediate between non-voter and voter.' Just as, for legal purposes, a juvenile changes into a voter as midnight strikes on the eighteenth birthday, so zoologists always insist on classifying a specimen as in one species or another. If a specimen is intermediate in actual form (as many are) zoologists' legalistic conventions still force them to jump one way or the other when naming it. Therefore the creationists' claim that there are no intermediates has to be true by definition at the species level, but it has not implications about the real world - only implications about zoologists' naming conventions.

To look no further than our own ancestry, the transition from Australo pithecus to Homo habilis to Homo erectus to 'archaic Homo sapiens' to 'modern Homo sapiens' is so smoothly gradual that fossil experts are continually squabbling about how to classify particular fossils. Now look a the following, from a book of anti-evolution propaganda: 'the finds have been referred to either Australopithecus, and hence are apes, or Homo and hence are human. Despite more than a centruy of energetic excavation and intense debate the glass case reserved for mankind's hypothetical ancestor remains empty. The missing link is still missing.' One is left wondering what a fossil has to do to qualify as an intermediate. In fact the statement quoted is saying nothing whatever about the real world. It is saying something (rather dull) about naming conventions. No 'missing link', however precisely intermediate it was, could escape the teminological force majeure that would thrust it one side of the divide or the other. The proper way to look for intermediates is to forget the naming of fossils and look, instead, at their actual shape and size. When you do that, you find that the fossil record abounds in beautifully gradual transitions, although there are some gaps too - some very large and accepted, by everybody, as due to animals simply failing to fossilize. In a way, our naming procedures are set up for a pre-evolutionary age when divides were everything and we did not expect to find intermediates.

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