The fundamental ideas behind the theory of evolution have been scientific gospel for decades - and yet creationists refuse to go the way of the dinosaurs. Who exactly are they? And just what do they believe? Stephen Moss reports

They do it differently in the US. The Creation Museum in Petersburg, Kentucky (motto: "Prepare to believe!") measures 70,000 sq ft, cost $27m to build, was designed by someone from Universal Studios, and promises "murals and realistic scenery, computer-generated visual effects, over 50 exotic animals, life-sized people and dinosaur animatronics, and a special-effects theater complete with misty sea breezes and rumbling seats". The museum, opened in 2006 by creationist group Answers in Genesis to promote "true history", looks Edenic on its website.

By contrast, Britain's creation museum, Genesis Expo, is housed in a former bank next to the bus station on the harbour front in Portsmouth. It does not appear to have any connection with Hollywood, and is an animatronic-free zone. The sign stretching across the front of the building is peeling, an elderly volunteer from a local church is manning the front desk, and the museum is only slowly converting its stock of creationist videos to DVD. The upside is that Genesis Expo is free to enter.

The museum was opened in 2000 by the Creation Science Movement, which claims to be the oldest creationist movement in the world, beginning life in 1932 as the Evolution Protest Movement. In 1935, Sir Ambrose Fleming, one its founders, explained at a public meeting why the movement was necessary: "Of late years, the Darwinian anthropology had been forced on public attention by numerous books in such a fashion as to create a belief that it was a certainly settled scientific truth. The fact that many eminent naturalists did not agree that Darwin's theory of species production ... was generally repressed." The CSM still quotes his words as its credo today, and in Darwin's bicentenary year Fleming's successors think they are finally making progress.

The bicentenary has been good for Genesis Expo. David Attenborough extolling the virtues of Darwin on TV - and attacking the vices of militant creationists, who he says have subjected him to hate mail, in the Radio Times - has been bringing in the punters. On the Saturday that I drop by, there is a steady trickle of somewhat bemused visitors - small church groups, a few young foreign tourists and several children eager to play with the dinosaurs.

Creationism has surprisingly little difficulty accommodating dinosaurs. Indeed, the first thing you bump into at the museum is Boris, a 20ft model of a tyrannosaurus rex. Conventional scientists think T-rex died out at the end of the Cretaceous period, about 65m years ago. Creationists, who argue that the world was created no more than 10,000 years ago, believe dinosaurs and man co-existed in the pre-Flood period (they date the Flood to around 1,600 years after the creation), that there were dinosaurs on the ark, but that they were eventually wiped out by the changes in climate which followed the Flood.

The museum itself is a little dusty, with lots of fossils in glass cabinets, the way museums were circa 1935. The high spots are a faux-marble gravestone on which Darwin's picture is engraved, above the caption "Here Lies the Theory of Evolution. RIP", and a batch of "genuine dinosaur eggs".

Ross Rosevear, the museum's curator, tells me he has been licking envelopes for the CSM since 1981 and is a convinced "young earther". Almost all Christians used to go along with the idea that Genesis was a bit suspect on dates, and that the six days of the Bible were metaphorical, with each day representing a vast geological age. The majority of Anglicans, theistic evolutionists who have no difficulty in believing in a Darwinian God, would still abide by that. But the publication in 1961 of Henry Morris and John Whitcomb's The Genesis Flood, which set out to give a scientific demonstration of the literal truth of the Bible, emboldened those who refused to accept evolution.

"The book was the turning point," says Rosevear. "They were voices in the wilderness at the time, but since then things have moved in that direction." A recent survey, commissioned by the theology thinktank Theos, reported that half of a sample of more than 2,000 people in the UK did not believe in evolution, almost a quarter opted for creationism or intelligent design (the latter presupposes a watchmaker with 20/20 vision who is not the Christian god and may well own a spaceship), and a remarkable 10% accepted young earth creationism.

If you believe in young-earth creationism, as an increasing number of evangelical Christians do, virtually all existing science has to be rewritten - and the creationists are ready to do the rewriting. The speed of light, Rosevear argues, used to be 300 times faster than it is now - necessary for creationists to explain cosmology and the distance of other solar systems from our own; the great cataclysm of the Flood explains the formation of sedimentary rock and the distribution of fossils; the division of the land masses occurred when the post-Flood ice melted and sea levels rose; dinosaurs died out because they couldn't adapt to the fall in oxygen levels that followed the Flood.

The theories are at best antediluvian, at worst absurd, so creationists feel more comfortable picking generalised holes in Darwinian thinking. "Most scientists believe in evolution because they believe that most scientists believe in evolution," says the evangelical preacher and author Brian Edwards. "We do believe in evolution, that things develop. But there's not a shred of evidence for macro evolution - the jump from one species to another. The fins of a fish can't become the wings of a bird or the arms of a man. All we know of genetics is that you can't have a half-formed eye; you can't have steps towards a fully formed eye. All that we know of the genome system supports creationism, not evolution. It's not just a matter of our faith; it's an intellectual issue. Darwin's had an easy ride. He's not the great hero."

"We are forever being told [by evolutionists] that they've got proof of evolution, but they haven't," says Monty White, former head of Answers in Genesis in the UK. "They've got proof of change within species. But the Bible doesn't teach fixity of species; it talks about kinds. You can't extrapolate from change within species to say that an ape-like creature can turn into man."

White, who is a chemist, could claim to be the grand old man of creationism in the UK. He became a Christian as an undergraduate in 1964, and initially accepted theistic evolution, but by the early 1970s he had come to believe that evolution was not compatible with Christianity. He admits that his thinking on creation is a "faith position", and wants evolutionists to do the same. "I object to the fact that evolution is taught as fact, rather than as a hypothesis. You're allowed to question everything in this country except evolution."

From the 1970s on, White spent much of his time writing on creationism and touring churches lecturing on the subject. His evangelism was important in building the movement - Geoff Chapman, who now runs the Creation Resources Trust in Somerset, says hearing White speak was his inspiration for getting involved in 1981 - and a loose federation of creationists, working through the network of evangelical churches, began to evolve.

There are now at least half a dozen active creationist organisations in the UK. The Leicester-based Answers in Genesis, with four full-time staff, is the most visible. Former science teacher Paul Taylor, who took over from White as head of AIG in the UK last year, says it has the largest "reach" of any creationist group in Britain and calls his organisation the "David Attenboroughs of the creationist world". "Creationists are less marginal than we were 20 years ago," he says. "There is greater respect for us than there was, and [as a result] more anger among the 'new atheists'. They want to clamp down on what children can be taught, which is what they accuse us of."

Other groups are smaller. The Creation Science Movement in Portsmouth says it has a mailing list of 1,500; Creation Research UK - an offshoot of an organisation set up by another former science teacher, John Mackay, in Australia more than 20 years ago - has 2,000. But names are duplicated across organisations, and some are anti-creationists keen to keep tabs on the enemy. As for the number of frontline creationists, involved in evangelising on a day-to-day basis, a delegate at a recent creationist conference at High Leigh in Hertfordshire told me there were about a hundred, in regular contact with each other via a subscriber-only internet site called Creation Link.

British creationism is surprisingly independent from the far bigger, better funded, more vocal, highly politicised movement in the US, where creationists and intelligent design organisations (often a front for Christian creationists) are fighting perpetual legal battles to get creationist teaching into the classrooms of state schools.

George Bush and Sarah Palin both appeared to give succour to the creationists. "Teach both," said Palin when she was running for the governorship of Alaska. "You know, don't be afraid of information. Healthy debate is so important and it's so valuable in our schools." So far the courts have treated creationism as a branch of religion and legislated to keep it out of the classroom on the grounds of the separation, enshrined in the constitution, between state and church.

That is the official position, but the reality is fuzzier. A survey last year suggested that 16% of American science teachers are creationist, and there is anecdotal evidence to suggest that creationism is taught, or at least discussed, in US schools. When we met recently, John Mackay, the founder and international director of Creation Research, told me he had lectured in many state schools in the US. Moreover, there is a large Christian school and university sector in the US, as well as a burgeoning home education sector which is to a large extent religiously oriented. So, whatever the American judicial system may decree and the science lobby may wish, creationism is being taught to children, in accordance no doubt with the wishes of the 45% of those who in a Gallup poll in the US in 2001 identified themselves as creationist (choosing, from several options, the statement "God created human beings pretty much in their present form at one time within the last 10,000 years or so" as the one closest to their own view).

Whether creationism or intelligent design should form part of science teaching is also the most controversial aspect of the debate in the UK. AIG's Taylor, a Christian since he was 17, says that when he was a teacher, "I didn't see it was part of my job to teach creationism, but if discussion came up it was possible to discuss creationism." That accords with government guidelines on how to treat creationism in the classroom. "Creationism and intelligent design are not part of the science national curriculum programmes of study and should not be taught as science," state the guidelines. "However, there is a real difference between teaching 'x' and teaching about 'x'. Any questions about creationism and intelligent design which arise in science lessons, for example as a result of media coverage, could provide the opportunity to explain or explore why they are not considered to be scientific theories and, in the right context, why evolution is considered to be a scientific theory."

Much is left to the discretion of individual teachers, and a spokesman for the Department for Children, Schools and Families says it is the job of headmasters to monitor what is being taught. He also encourages parents to report teachers they believe to be overstepping the mark. "If you are teaching evolution and a child raises his hand and says, 'But I've heard we were created by God', there's nothing wrong with having a discussion about it. That's common sense. But teachers can't teach creationism, and Christian teachers have to follow the rules."

Last year, Michael Reiss, professor of science education at the Institute of Education, lost his job as director of education at the Royal Society when members of the society objected to his call for creationism to be discussed in science lessons. It was a bizarre episode because Reiss is a theistic evolutionist and he was arguing for no more than the government guidelines already permit. What did for him was his suggestion that "creationism is best seen by science teachers not as a misconception but as a worldview", which was misconstrued as an argument for giving creationism and evolution equal weight.

Reiss is wary of re-igniting the controversy and prefers not to talk about the way in which he was ousted. But he does tell me that he feels creationism is becoming stronger, and that it is better to engage with it rather than ignore or show contempt for it. "It is growing, both in the UK and in many other countries," he says. "As Christianity has become less important in the west, it has sometimes become more extreme. That is a common phenomenon. The rise of creationism makes teaching more challenging. In the US a lot of pressure has been brought to bear by local school boards, and as a result the state system in the US teaches no evolution at all, or else teaches a very eviscerated, attenuated form of it. My hope is that we can avoid the extreme politicisation of the US."

It may be a vain hope. Attenborough says he has received hate mail from creationists, though all the organisations declare they would never resort to such tactics. But the creationists, too, complain of hate mail, and Randall Hardy of Creation Research UK sent me a copy of a recent exchange in which the term most frequently resorted to by his correspondent was "religious parasite". I suspect if anyone could be bothered to trawl through a good sample of emails and discussion board messages where these issues are being debated, I am confident that they would find a much higher percentage of abuse is aimed at Christians by atheists, than vice versa," he says.

The viciousness reflects the fact that, at its heart, this is not a scientific debate but a moral, cultural and political one. John Mackay, the founder of Creation Research, is frank about his agenda and admits this is really a battle of worldviews. "All scientific research, whether we like it or not, has moral overtones and implications and applications," he says. "This issue is fundamental to the whole of life. When your government is making decisions about stem-cell research, sooner or later you have to address the issue of, 'Well, did God make us or didn't he make us?' When you're funding abortions, are we going to be held accountable after the grave? It's not an issue you can just shove aside as if it doesn't matter. If life came from nature, it doesn't matter; we're just hydrogen recycled; we'll come back again maybe. Science is not just test tubes. There's always a wider worldview, and that's where the bitterness comes from."

One of the most corrosive arguments creationists deploy - and I heard it many times - is that Darwinism made possible eugenics, Nazism, communist materialism. "If we come from slime and revert to slime, it's not surprising that life is slimy," is one mantra. "If you realise what Darwin gave rise to, you would realise what a pernicious system it was," says Brian Edwards. "Eugenics and Nazism applied biological evolution quite logically." Creationists like to point to the original title of Darwin's life-redefining book: "On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life". Favoured races! QED, they say with satisfied expressions. Darwin as the godfather of Hitler and Stalin. No wonder this debate degenerates into vicious blogs and hate mail, and a reasonable man like Michael Reiss gets submerged in the flood.

The US and UK creationist movements have many points of difference, so at the High Leigh conference - seven lectures grouped under the banner "Genesis Kinds: Creationism and the Origin of Species" - it is interesting to see the two genuses side by side. Todd Wood, director of the Center for Origins Research at Bryan College (motto: "Christ above all") in Dayton, Tennessee, and the prime mover in the event, doesn't want to talk to me. He won't even let me record his lecture on Darwin, about whom he evidently has mixed feelings. During the talk, he shows a slide of himself outside Down House, Darwin's home in Kent, and his concluding remarks are affectionate, if condescending: "Darwin's was a sad life. He was a brilliant man who ignored the Lord's pursuit of him. God was after him, but he allowed the hardships he faced [Wood is thinking principally of the death of Darwin's young daughter] to harden him."

The conference's co-organiser, Paul Garner, a geologist who works full time for Biblical Creation Ministries, is also initially reluctant but explains why standing up for the literal truth of Genesis is so important to him: "Many people have the mistaken impression that it's Genesis, chapter one that drives young earth creationism - a rigid understanding of the word 'day' in the creation. But that isn't it at all. It's Genesis three; it's the introduction of death and suffering and what you might call natural evil into the creation. If those things pre-date Adam, there's a big theological problem for me, because it undermines the foundation of the gospel. The young-earth position is the only one that has a coherent understanding of the history that doesn't have suffering, death and bloodshed before Adam's fall." It is, in other words, a life-or-death issue for Christianity: if evolution is true, the creation is founded on competition, suffering and mortality; there never was a paradise; a theistic evolutionist God is an accessory to eternal crime.

Sylvia Baker, another veteran creationist, biologist, former teacher and author of the anti-evolutionary bestseller, Bone of Contention, is a rare female creationist. "The first time I'd come across evidence for evolution was in A-level zoology," she says, "and it had struck me as rather weak. It seemed circumstantial, and I thought there must be more evidence than this because all of these things are vague and capable of different interpretations. I assumed that when I got to university all the vagueness would disappear and there'd be lots of overwhelming evidence. But there wasn't. I still didn't query it, but a turning point came towards the end of my degree when in a seminar on the supposed evolution of the eye it suddenly seemed to me an impossibility that the vertebrate eye could have evolved from other sorts of structures [eyes of invertebrates]. The two things run on completely different principles. There's just no connection. So I said, 'Maybe it didn't happen.' What happened next really taught me a lesson, which the subsequent 40 years have substantiated. There was a shocked silence, somebody started mocking me for my belief in God and the seminar leader said, 'Quiet. I will not have this. I refuse to get involved in any controversy. We will not discuss this.'"

That moment governed the rest of Baker's life, which has been spent teaching in private Christian schools, writing on creationism, and working with the Biblical Creation Society, another of the mosaic of similar-sounding organisations which articulate creationism in the UK. She seems genuinely questioning, but what worries me about many of her fellow creationists is that they begin with the Bible and then start looking for scientific evidence to back up what their faith tells them is true.

"I am guided ultimately by the parameters that the Bible lays down," admits John Peet, travelling secretary of the Biblical Creation Society. He estimates that 90% of the congregation at the Chertsey Street baptist church in Guildford, where he worships and where I hear him address the "creation club", are young earthers. The theme of pastor John Benton's sermon in the evening is "Genesis and Evolution: Do They Fit Together?" He holds up a recent New Scientist cover, headlined "Darwin was wrong," as evidence that the scientific base for evolution is crumbling, that the Darwinian tree of life can be uprooted.

Mackay, too, is clutching a copy of that issue of New Scientist when I meet him. This is manna from heaven - the science establishment offering up gifts to the creationists. They also claim that the aggression of the new atheists is helping them. They paint Dawkins as a "recruiting sergeant" for creationism because he links evolutionary thinking with atheism. "He has been a real help to the ministry, " says Randall Hardy.

Creationists argue that the new atheists are fuelling the dogmatism; Richard Harries, the former Bishop of Oxford and a theistic evolutionary, last week threw that accusation back at them. "Creationists totally misunderstand the Bible," he said. "Genesis is in the business of story, myth, poetry, metaphor. They [creationists and atheists] feed off one another. The debate has an unreality about it. Those of us who are not fundamentalists can't find a place."

But Greg Haslam, pastor at Westminster Chapel in central London, says a lot of people don't understand what is lost by compromising. "[Jesus] seems very clearly to have believed in the historicity of Adam and Eve. If you don't believe those early chapters [of Genesis], you end up saying, 'Well, Jesus was wrong,' and where does that leave you? What can we believe of what Jesus said?"

If, like Haslam, you take the biblical beginning literally, you must also go along with the biblical end - apocalypse, the second coming of Christ, the final judgment, eternal damnation for non-believers, perpetual bliss for the lucky few. It was this that really turned Darwin off Christianity: inherent in creationism is destructionism. It strikes me, too, as a hideous doctrine, and over dinner at High Leigh I ask Kurt Wise, professor of science and theology at the Southern Baptist Theological College in Louisville, Kentucky, whether I've understood it correctly. Wise is a twinkling 50-year-old with a perpetual smile, a contrarian spirit and a born (or born-again) preacher's style of delivery. Wise imagines creation as "a beautiful painting or tapestry where each individual brushmark or thread is one aspect of the creation". But on the apocalypse that awaits us he is unbending. "The Bible warns us: 'As it was in the days of Noah, so it shall be - my coming.' People are going to be wandering around on the planet when the Flood comes and they're blown away. People are going to be eating and drinking and marrying and doing their thing, and the judgment is going to come." Then he returns to his apple pie and custard, smiling at the thought of the world's imminent demise.

God vs Darwin: Do creationists have a case?

In the 150 years since the publication of On the Origin of Species, Darwin's opponents have tried numerous angles of attack to discredit the man and spear his theory. He was lampooned in Victorian caricature as a bearded monkey, his critics have misrepresented his theory by likening it to a whirlwind in a junk yard assembling a jumbo jet by chance and they drone on endlessly about gaps in the fossil record between one group of creatures and another – even though numerous such transitional fossils have been found. Most Darwin-sceptics, of course, hold up the Bible as "proof" that the great biologist can't be right.

A more subtle ploy is to damn the man with faint praise. In a letter in the Telegraph to coincide with Darwin's birthday last week, 10 authors conceded that "evolutionary adaptation, modification and variation within species – which is what Darwin actually discovered – is secure" but that the evidence for how complex organisms developed is "modest in the extreme". What they seem to be saying is that a finch's beak can change over generations to allow it to eat a different type of food, for example, but where did the finch come from in the first place? By accepting the carefully worded "variation within species" they are implicitly rejecting speciation – the process by which one species becomes two that cannot interbreed. In reality there is now stacks of evidence for how speciation can occur. Scientists have studied it in great detail happening in the lab – for example in fruit flies.

There are still scientific debates to be had about the details of how natural selection operates – for example, to what extent characteristics acquired during life can be passed on to off spring via chemical modifications to DNA – but there is no serious disagreement in the scientific community about the fundamentals of Darwin's theory. A century and a half of science from fossils to DNA has turned up nothing that would bring Darwin's theory down. In fact, it has made his defences stronger.

James Randerson

• This article was amended on Thursday 19 February 2009. The Creation Museum is seven miles west of Cincinnati Airport, but it is not in Cincinnati as we reported. It is on Bullittsburg Church Road in Petersburg, Kentucky. This has been corrected.