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08 September, 2006

A Critique of Intelligent Design

This is part two of a three part posting. Read part one first.

Intelligent design is an idea intended to provide an alternative to evolution for those who are so bound by religious dogma that they cannot accept that the Universe is more than a few thousand years old. Because the Bible appears to tell them that the Universe is very young and that a magic being created people ‘in its own image’, they are unable to accept the vast and overwhelming geological, biological and cosmological evidence to the contrary. Fair enough. But, annoyingly, they also don’t want the rest of us to accept it either. So they feel the need to challenge science – because science is the ogre that is amassing all this overwhelming evidence and coming up with all these reasonable explanations for it that they don’t like.

The bit of science that Christian fundamentalists hate most is the theory of evolution by natural selection. They have tried for years to criticise evolution, saying it hasn’t been proven, that there are ‘missing links’ that can’t be explained, and so on, but (as is the way with science) the evidence keeps on accumulating and the good ideas, like evolution, just get stronger and stronger because of it. So now they have taken a new tack. Now they say that evolution is fundamentally flawed because one of its fundamental premises is wrong.

The argument for evolution rests on the notion that small variations that can occur when living things reproduce, may help or hinder the organism that inherits them as it attempts to survive and reproduce in its environment. If the changes help, the organism will be successful and will pass them on because the offspring will be like the parent. If they hinder, then the organism will be less successful and, even if it manages to reproduce, its unhelpful trait will eventually be lost from the population. In this way, organisms develop and adapt to the environments they inhabit, gradually changing and becoming better suited to it. A consequence of this argument is that every aspect of any organism alive today must have developed from something that was there before – new bits don’t just appear fresh and whole, they all come from small, incremental changes to bits that were there already.

This is actually quite a hard requirement to swallow when you look at the astonishing complexity and interdependence of all the parts of modern life-forms. For many years, the human eye was held up as an example of something so complicated that it just could not possibly have evolved. It just had to have been made by magic. Recently, however, people like Richard Dawkins have put together convincing stories about how eyes of ever-increasing complexity and usefulness could have arisen from very simple beginnings. Similarly for hands, feathered wings, brains and all the other marvels of modern biology, a path can be traced back through time. To cut a long story short, the anti-evolutionists are finding it ever more difficult to use the ‘impossibly complex’ argument because new evidence keeps accumulating and once-missing links in the fossil record keep turning up.

So the Christian fundamentalists have sought out new examples and new ways of phrasing their complexity argument and they have come up with the notion of ‘irreducible complexity’. The essence of this is that some complex systems cannot be broken down into simpler parts that are still functional. The definitive example of this is the flagellum, used by some bacteria to propel themselves through liquids. A flagellum comprises a long tail that fits into a small cup. The cup is a tiny motor that twirls the tail and pushes the bacterium along. Neither tail nor cup is of any obvious use on its own, say the irreducible complexity proponents, so this system could not have evolved. They then take a massive leap away from rationality and go on to say, therefore, these things must have been designed by an ‘intelligent designer, and that was probably God.

But this step does not follow at all. First of all, just because no-one can see what use they may have been to a bacterium separately, doesn’t mean they were of no use. What kind of arrogance is that? Because we can’t understand something it can’t exists? Because we can’t solve the puzzle it can only be solved by magic? Given the countless examples where we have studied things for generations, scratching our heads, and then finally worked it out, wouldn’t it be more reasonable to assume we just don’t know enough yet? Or that this is going to take a lot of people a long time to work out? This is where intelligent design is clearly nonsense and obviously unscientific. Because something looks ‘irreducibly complex’ does not warrant the conclusion that, therefore, it must have been designed by God! That isn’t a theory, that’s just shrugging your shoulders and saying ‘I dunno, probably God did it.’ It certainly isn’t a theory in the scientific sense of an explanation that covers all the known evidence, is compatible with all the existing theories in this and other fields, and makes clear and specific predictions that can be tested experimentally. So it’s not good logic and it sure ain’t science.

Worse still, even on it’s own terms, it fails as an explanation. Maybe there is some biological reason I’m not aware of but it seems odd to me that intelligent design proponents seem to be insisting that every component in every living organism must itself have evolved. Yet we know that cells of all types often incorporate bits and pieces from their environment – sometimes even other cells or viruses – to use as tools in their struggle for survival and reproduction.

Let’s assume that flagellae are, in fact, irreducibly complex – that the parts have no biological use on their own. That does not prevent them each arising in some other, normal and natural way and then having been adopted by bacteria and put together as cool outboard motors. If you’ve been following some of the nanotechnology research over the past few years, you’ll know that it is quite reasonable to believe that combining complex molecules – using nothing more spooky than the usual laws of physics – can lead to tiny machines that do all kinds of interesting things.

There’s a little machine, for example, that can walk along the inside of a cell wall and carry chemical passengers on its head. It is believed that nerve cells use these microscopic automata to take the building blocks of neurotransmitters from the cell’s body, where they are made, along the long nerve fibres to the synapses, where they are assembled and used. The little walking machine is put together from two molecules – each naturally occurring in the cell’s surroundings – and they form a little V-shaped pair of legs. The V scissors open and closed because of how the chemicals interact at the ‘hinge’ end and as it opens it pushes the front end forwards and when it closes, it pulls the back end forwards. (Put your fingers together on a tabletop with your thumb behind to make an arch. Keeping your fingers still, pull your thumb up to your fingers. Then, keeping your thumb still, push your fingers out to make the arch again. That’s how it ‘walks’.) These machines are assembled (by putting the two ‘leg’ molecules together in the cell body. They then march off down the nerve fibre with their chemical loads attached and are then disassembled and returned to the environment.

The cells that first evolved to use these little robots would have had the evolutionary advantage of being able to grow longer nerve fibres. However, in ‘intelligent design’ terms, they are irreducibly complex. Their components don’t do anything. The point is, these components did not have to evolve – they’re just ordinary molecules. What evolved was the cell that developed the trick of putting them together (and later, evolved longer nerve fibres because that was now possible and beneficial.)

It’s the same for the flagellum; the cup is a miniscule molecular motor, the tail is a long protein molecule. Neither has any obvious use on its own but it could be that versions of these components arose naturally in the environment of the bacteria that developed the trick of putting them together. However crudely they worked at first, some movement is better than none and it may well have conferred a significant advantage. Once incorporated into the bacterium, they would then have evolved towards greater efficiency and better control.

This may not be the right explanation but at least it’s consistent with other things we know, it’s vaguely plausible, and it is testable (if we look, do we find protein strings and molecular motors occurring naturally and in the same environment?)

Ready to read the next part?

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