I once found a watch on the road. It is obviously designed by an intelligent maker, an unknown (at least to me) directed intelligence. That's fine, we all accept that. Another time, I found a cat. This time, I did not assume it was made by a directed intelligence. Why?
Well, the above example is a bastardisation of an example given by William Paley in his 1802 work, "Natural Theology". In it, he claimed that, such was the complexity of biological structures, they could only have been designed by a divine intelligence.
Of course, such arguments have since been roundly refuted, but their proponents still exist. I do not wish to disrespect (is that even a word? I never liked it, but hey, I don't have a synonym) anyone's religious faith, but it is imperative to avoid the sort of woolly thinking that has allowed Creationism to flourish in the world, 145 years after the publishing of Darwin's "The Origin of Species". (Incidentally, despite my own personal disbelief in the existence of any deity, I do not feel a personal religious belief is necessarily antithetical to the pursuit of scientific knowledge, it just makes it bloody difficult.)
Most of the arguments for Creationism (or Intelligent Design, as it is now called) have been dealt with by authors more eloquent than I, but I think there is one particularly salient point that needs to be focused on. A cat is not a watch...
This is not the same point as Magritte's "Ceci n'est pas une pipe", nor is it a statement of the blindingly obvious, it is rather the lynchpin of the whole notion of Evolution.
A watch is, of course, an artificial, non-biological object. It, unlike a cat, is built from non-living parts and assembled by hand or machine and each part is discrete and unrelated to the others until assembled. This is one of the biggest issues with the concept of Intelligent Design, it is essentially saying that a cat must be assembled from discrete components like a watch and must spring forth as a whole organism. In this case, we can see a Divine Mechanic, stooped over a giant workbench, shouting exasperatedly "Where the @%&* is that bloody spleen, it was here 5 aeons ago?!?"
The point is, the parts of a watch are fashioned to an end. They are (I'm taking the example of Paley's putative mechanical watch here) base metal melted and fashioned into specific shapes that only make sense when added into the whole of the watch.
A cat on the other hand is really an expression of a fractal code. It is not a series of discrete components. Its parts are inter-related and cannot be arrived at without the rest of the body. This can be easily seen in the foetus, as instructions are sent to undifferentiated cell masses, which then become body parts. Of course, this is, at first glance, far more complex and wondersome than the relatively simple task of assembling a watch, but I will show that when looked at from an evolutionary standpoint, it's actually quite simple.
The issue is here is the relative myopia of most people's historical vision. It's not our fault that we tend to be somewhat ignorant and unappreciative of the vast length of time that has passed since the beginning of life on this planet. Most of our interactions take place in a matter of minutes or hours and the longest of human lifespans take up no more than 100 years. Trying to think back 4,500,000,000 years is a daunting process, but this is how long the Earth has been in existence.
It now seems that life did not take very long to evolve, once the surface of the earth had cooled. In fact, the estimate is revised backwards all the time, with some evidence showing that life arose a scant 500 million years after the surface cooled.
This life didn't seem to do much for the 3.35 billion years, simply sitting there as algal mats, changing the inhospitable (at least, for us) carbon dioxide and methane atmosphere into the toxic (for some of them) oxygenated atmosphere we know today.
Herein, we see one of the main points of the argument against the necessity for an Intelligent designer. Although a world covered in photosynthetic slime may seem dull to us, this would have been a vast proving ground for life's basic principles and the sheer length of time would have given ample opportunity for some interesting features to arise.
What are these features and how did they come about? Well, that's a story for tomorrow