Evolution happens.

What remains open to dispute, especially among scientists, is how evolution happens. Scientific theories themselves evolve, adapting to fit new observations, new discoveries, and new interpretations of old discoveries. Theories are not carved in tablets of stone. The greatest strength of science is that when faced with sufficient evidence, scientists change their minds. Not all of them, for scientists are human and have the same failings as the rest of us, but enough of them to allow science to improve.

Even today there are diehards - not a majority, despite the noise they make, but a significant minority - who deny that evolution has ever occurred. Most of them are American, because a quirk of history (coupled with some idiosyncratic tax laws) has made evolution into a major educational issue in the United States. There, the battle between Darwin's followers and his opponents is not just about the intellectual high ground. It is about dollars and cents, and it is about who influences the hearts and minds of the next generation. The struggle masquerades as a religious and scientific one, but its essence is political. In the 1920s four American states (Arkansas, Mississippi, Oklahoma, and Tennessee) made it illegal to teach children about evolution in public schools. This law remained in place for nearly half a century: it was finally banned by the Supreme Court in 1968. This has not stopped advocates of `creation science' from trying to find ways round that decision, or even to get it reversed. Largely, however, they have failed, and one reason is that creation `science' is not science; it lacks intellectual rigour, it fails objective tests, and at times it is plain nutty.

It is possible to maintain that God created the Earth, and no one can prove you wrong. In that sense, it is a defensible thing to believe. Scientists may feel that this `explanation' doesn't greatly help us understand anything, but that's their problem; for all anyone can prove, it could have happened that way. But it is not sensible to follow the Anglo-Irish prelate James Ussher's biblical chronology and maintain that the act of creation happened in 4004 BC, because there is overwhelming evidence that our planet is far older than that - 4.5 billion years rather than 6000. Either God is deliberately trying to mislead us (which is conceivable, but does not fit well with the usual religious messages, and may well be heretical) or we are standing on a very old lump of rock. Allegedly, 50 per cent of Americans believe that the Earth was created less than 10,000 years ago, which if true says something rather sad about the most expensive education system in the world.

America is fighting, all over again, a battle that was fought to a fmish in Europe a century ago. The European outcome was a compromise: Pope Pius XII did accept the truth of evolution in an encyclical of 1950, but that wasn't a total victory for science.[1] In 1981 a successor, John Paul II, gently pointed out that `The Bible ... does not wish to teach how the heavens were made, but how one goes to heaven.' Science was vindicated, in that the theory of evolution was generally accepted, but religious people were free to interpret that process as God's way of making living creatures. And it's a very good way, as Darwin realised, so everyone can be happy and stop arguing. Creationists, in contrast, seem not to have appreciated that if they pin their religious beliefs to a 6000-year-old planet, they are doing themselves no favours and leaving themselves no real way out.

Darwin's Watch is about a Victorian society that never happened - well, once the wizards interfered, it stopped having happened. It is not the society that creationists are still attempting to arrange, which would be far more `fundamentalist', full of self-righteous people telling everyone else what to do and stifling any true creativity. The real Victorian era was a paradox: a society with a very strong but rather flexible religious base, where it was taken for granted that God existed, but which gave birth to a whole series of major intellectual revolutions that led, fairly directly, to today's secular Western society. Let us not forget that even in the USA there is a constitutional separation of the state from the Church. (Strangely, the United Kingdom, which in practice is one of the most secular countries in the world - hardly anyone attends church, except for christenings, weddings, and funerals - has its own state religion, and a monarch who claims to be appointed by God. Unlike Discworld, Roundworld doesn't have to make sense.) At any rate, the real Victorians were a God-fearing race, but their society encouraged mavericks like Darwin to think outside the loop, with far-reaching consequences.

[1] According to Isaac Asimov, the most practical and dramatic victory of science over religion occurred in the seventeenth century, when churches began to put up lightning conductors. The thread of clocks and watches runs right across the metaphorical landscape of science. Newton's vision of a solar system running according to precise mathematical `laws' is often referred to as a `clockwork universe'. It's not a bad image, and the orrery - a model solar system, whose cogwheels make the tiny planets revolve in some semblance of reality - does look rather like a piece of clockwork. Clocks were among the most complicated machines of the seventeenth and eighteenth centuries, and they were probably the most reliable. Even today, we say that something functions `like clockwork'; we have yet to amend this to `atomic accuracy'.

By the Victorian age, the epitome of reliable gadgetry had become the pocket-watch. Darwin's ideas are intimately bound up with a watch, which again plays the metaphorical role of intricate mechanical perfection. The watch in question was introduced by the clergyman William Paley, who died three years after Darwin was born. It features in the opening paragraph of Paley's great work Natural Theology, first published in 1802.[1] The best way to gain a feeling for his line of thinking is to use his own words: In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that for anything I knew to the contrary, it had lain there forever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given, that, for anything I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? Why is it not as admissible in the second case, as in the first? For this reason, and for no other, viz. that, when we come to inspect the watch, we

[1] It is old enough to use the elongated s's parodied in Discworld as is. We have resisted temptation except in this footnote. Though 'manifestation of design' does have a bit of a cachet. perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point to the hour of the day; that if the different parts had been differently shaped from what they are, of a different size from what they are, or placed after any other manner, or in any other order, than that in which they are placed, either no motion at all could have been carried on in the machine, or none which would have answered the use that is now served by it.

Paley goes on to elaborate the components of a watch, leading to the crux of his argument: This mechanism being observed ... the inference, we think, is inevitable; that the watch must have had a maker; that there must have existed, at sometime, and at some place or other, an artificer or artificers, who formed it for the purpose which we find it actually to answer; who comprehended its construction, and designed its use.