Thursday, February 08, 2007

Evolutionary Mechanisms: Part One

Does Evolution Even Have a Mechanism? by William Dembski contains polemics in support of ID. I'll focus on a portion for purposes of commentary. Dembski in italics.

Suppose, therefore, for the sake of argument that intelligence--one irreducible to material mechanisms--actually did play a decisive role in the emergence of life's complexity and diversity. How could we know it? To answer this question, let's run a thought experiment. Imagine that Alice is sending Bob encrypted messages over a communication channel and that Eve is eavesdropping. For simplicity let's assume all the signals are bit strings. How could Eve know that Alice is not merely sending Bob random coin flips but meaningful messages?

To answer this question, Eve will require two things: First, the bit strings sent across the communication channel need to be reasonably long--in other words, they need to be complex. If not, chance can readily account for them. Just as there's no way to reconstruct a piece of music given just one note, so there is no way to preclude chance for a bit string that consists of only a few bits. For instance, there are only eight strings consisting of three bits, and chance readily accounts for any of them.


The number of units in an analogous genome is sufficiently large to rule out chance explanations. But does necessity or selection explain the origins of an initial genome?

There's a second requirement for Eve to know that Alice is not sending Bob random gibberish: Eve needs to observe a suitable pattern in the signal Alice sends Bob. Even if the signal is complex, it may exhibit no pattern characteristic of intelligence. Flip a coin enough times, and you'll observe a complex sequence of coin tosses. But that sequence will exhibit no pattern characteristic of intelligence. For cryptanalysts like Eve, observing a pattern suitable for identifying intelligence amounts to finding a cryptographic key that deciphers the message. Patterns suitable for identifying intelligence I call specifications.

The specifications being analogous to genetic encoding conventions. Encoding conventions are not dictated by underlying forces of nature. If 'a' must follow 'c' a pattern is in evidence but not a code.

In sum, Eve requires both complexity and specification to infer intelligence in the signals Alice is sending to Bob. This combination of complexity and specification, or specified complexity as I call it, is the basis for design inferences across numerous special sciences, including archaeology, cryptography, forensics, and the Search for Extraterrestrial Intelligence (SETI).

A genome is characterized by complex specificity. Is CSI generated in the absence of intelligence? What are properties of a minimal genome and how do we determine a minimally functional genome? That is the subject of a future blog entry.

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