Monday, April 03, 2006


Why didn't the Wright Brothers, in my home town of Dayton, Ohio, just go ahead a design a Concorde rather than the rickety, barely able to fly, flying thing they did design? Dawkins has an answer for that too in The Ancestor's Tale, pages 601-603.

[OPEN QUOTE] And now for an important point. The evolution of any complex designoid organ in an arms race must have come about in a large number of steps of progressive evolution. Such evolution qualifies as progressive by our definition because each change tends to continue the direction of its predecessors. How do we know there are many steps rather than just one or two? By elementary probability theory. The parts of a complex machine, such as a bat's ear, could be rearranged at random in a million ways before you hit another arrangement that could hear as well as the real thing. It is statistically improbable, not just in the boring sense that any particular arrangement of parts is as improbable, with hindsight, as any other. Very few permutations of atoms are precision auditory instruments. A real bat's ear is one in a million. It works. Something so statistically improbable cannot sensibly be explained as the result of a single stroke of luck. It has to be generated by some sort of improbability-generating process, ratcheted up by what the philosopher Daniel Dennett calls a crane' (as opposed to a 'skyhook': the analogy is to the man-made lifting machine, not the bird). The only cranes known to science (and I would bet the only cranes there have ever been, or ever will be, in the universe) are design and selection. Design explains the efficient complexity of microphones. Natural selection explains the efficient complexity of bat ears. Ultimately, selection explains microphones and everything designed too because the designers of microphones are themselves evolved engineers generated by natural selection. Ultimately, design cannot explain anything because there is an inevitable regression to the problem of the origin of the designer.

Design and natural selection are both processes of gradual, step-by-step, progressive improvement. Natural selection, at least, could not be anything else. In the case of design it may or may not be a matter of principle, but it is an observed fact. The Wright brothers did not have a blinding flash of inspiration and promptly build a Concorde or a Stealth bomber. They built a creaking, rickety crate that barely lifted off the ground and lurched into a neighboring field. From Kitty Hawk to Cape Canaveral, every step of the way was built on its predecessors. Improvement is gradual, step by step in the same continued direction, fulfilling our definition of progressive. We could, with difficulty, conceive of a Victorian genius designing a sidewinder missile fully formed within his Zeusian, side-whiskered head. The notion defies all common sense and all history, but it does not instantly fall foul of the laws of probability in the way we would have to say of the spontaneous evolution of a flying, echolocating, modern bat.

A single macro-mutational leap from ground-dwelling ancestral shrew to flying, echolocating bat is ruled out just as safely as we can rule out luck when a conjuror successfully guesses the complete order of a shuffled pack of cards. Luck is not literally impossible in either case. But no good scientist would advance such prodigious luck as an explanation. The card-guessing feat has to be a trick—we've all seen tricks that appear just as baffling to the uninitiated. Nature does not set out to fool us, as a conjuror does. But we can still rule out luck, and it was the genius of Darwin to rumble nature's sleight of hand. The echo-ranging bat is the result of an inching series of minor improvements, each adding cumulatively to its predecessors as it propels the evolutionary trend on in the same direction. That is progress, by definition. The argument applies to all complex biological objects that project the illusion of design and are therefore statistically improbable in a specified direction. All must have evolved progressively. [CLOSE QUOTE]

No comments: