Intelligent Design ... and Bioinformatics

If you are interested in the background to the recent ruling against the teaching of Intelligent Design alongside Darwinian evolution in science classes, you might want to read a fine article on the subject, which also includes the judge's splendidly wise and perceptive remarks.

Of course, it is sad that the case even needed to be made. The idea that Intelligent Design - which essentially asserts that everything is as it is because, er, everything was made that way - can even be mentioned in the same breath as Darwinian evolution is risible. Not because the latter is sancrosanct, and cast-iron truth. But Darwin's theory is a scientific theory, testable and tested. So far, it seems to be a good explanation of the facts. Intelligent Design is simply a restatement of the problem.

Among those facts are the growing number of sequenced genomes. It has always struck me that DNA and bioinformatic analyses of it provide perhaps the strongest evidence for evolution. After all, it is possible to bung a few genomes into a computer, tell it to use some standard mathematical techniques for spotting similarities between abstract data, and out pops what are called phylogenetic trees. These show the likely interrelationships between the genomes. They are not proof of evolution, but the fact that they are generated without direct human intervention (aside from the algorithms employed) is strong evidence in its favour.

One of the most popular ways of producing such trees is to use maximum parsimony. This is essentially an application of Occam's Razor, and prefers simple to complicated solutions.

I'm a big fan of Occam's Razor: it provides another reason why Darwin's theory of natural selection is to be preferred over Intelligent Design. For the former is essentially basic maths applied to organisms: anything that tends to favour the survival of a variant (induced by random variations in the genome) is mathematically more likely to be propagated.

This fact alone overcomes the standard objection that Intelligent Design has to Darwinian evolution: that purely "random" changes could never produce complexity on the time-scales we see. True, but natural selection means that the changes are not purely random: at each stage mathematical laws "pick" those that add to previous advances. In this way, simple light-sensitive cells become eyes, because the advantage of being able to detect light just gets greater the more refined the detection available. Mutations that offer that refinement are preferred, and go forward for further mutations and refinement.

It's the same for Intelligent Design's problem with protein folding. When proteins are produced within the cell from the DNA that codes for them, they are linear strings of amino acids; to become the cellular engines that drive life they must fold up in exactly the right way. It is easy to show that random fluctuations would require far longer than the age of the universe to achieve the correct folding. But the fluctuations are not completely random: at each point there is a move that reduces the overall energy of the protein more than others. Putting together these moves creates a well-defined path towards to folded protein that requires only fractions of a second to traverse.