A dinosaur model on display at the Genesis ExpoNestled among the pubs of historic Portsmouth Harbour is a modest-looking building which houses a rather less modest project. The Genesis Expo, an almost quaint testament to, well, the Old Testament, is devoted to disproving the theory of evolution. Over twelve displays set in three darkened corridors, the Expo sets out its creationist stall. At first, it's all chillingly credible. Little gaps in evolutionary theory are rigorously examined. Missing links are held up as discovered holy grails around which evolution comes tumbling down.

Most of it, naturally, is selective. Examples are given which don't bear close scrutiny. A layer of volcanic rock at Mount St Helens proves that rock strata couldn't have taken millions of years to build up. The bombardier beetle's defence system proves that animals couldn't possibly have adapted. The fact that apes are "incapable of speech and do not paint pictures" proves that men and monkeys could not share a common ancestor.

The message of the museum is trumpeted so insistently that you may as well have an attendant standing by your side saying "See! See!" for the entire half-hour it takes to wind round the corridors. It may be rooted in faith rather than reason, but what's striking is how often this thoroughly unscientific exhibition appeals to science to provide its arguments. Like the Taliban, the 'creation science movement' rejects science, except the bits that suit its ends.

It's all presented like a budget version of the kids' bits of the Natural History Museum. There's the occasional button to press, and audio visual guides that bring to mind, both in tone and content, the weirdness of the recent BBC spoof science programme Look Around You. Soothing voices hypnotise you through odd-looking wooden speakers you hold to your ear, to a background of alarmingly outdated ambient music. It's a little unfortunate, or else devilishly cunning, that whichever display you're trying to listen to, the commentary for the next one is clearly audible, creating a disarming dissonance that could have been thought up by the US army's Psyops division to break down your defences.

The further you progress, the weirder it gets. One display case shows a tombstone engraved with the words "Here lies the theory of evolution" for no apparent reason. Pretty soon, though, it becomes glaringly clear why this place exists. Not to prompt debate about evolution, but to convert us.

Apparently, Chinese calligraphy proves that the story of Noah and the deluge is completely true. The character for 'boat' spells out the whole thing. Similarly, the brochure tells us: "Their word 'first' embodies the statement that God made man and breathed life into him." Of course, what's not explained is why, if the Chinese knew the truth of the Judeo-Christian creation myth, they all went on to be Buddhists.

The rationale for why Earth can't be more than 10,000 years old seems to rely on the slightly vexing proposition that the population doubles every generation. Conveniently, this doesn't take into account the masses supposedly killed in the self-same flood they insist really happened.

And then comes the finale of the walk-through tour. A great starscape is shown, and the reassuring voice on the speaker intones: "The Genesis Expo declares that this precise universe was designed meticulously, and that: 'In the beginning God created the Heaven and Earth.' Of course he did."

Of course he did. Because all you have to do is believe something and it will be true. Which is one of the reasons why this modest little exhibition is far from harmless.

For a start, it's got an absolutely brilliant location, right outside the train station for Portsmouth Harbour, where thousands go to tour the old warships moored at the naval dock.

Secondly, and even more insidiously, it seems to be aimed quite heavily at children. Inquisitive ten-year olds would go wild for an exhibition that promised fossils, dinosaurs, and an explanation of the world. And a gift shop, of course, complete with model dinosaurs (apparently, dinosaurs are accounted for in the Bible, so the creationists here don't have a problem with them: except for saying that they existed 6,000-10,000 years ago, when God created the world).

When I asked the exhibition attendant at the end of my tour why the science world was so against creationism, he shrugged: "Because they're atheists."

Of course they are.