The ultimate status symbol: How does Unesco whittle down the contenders for the World Heritage list?

As you survey the rolling Kentish Downs at the point where the garden of Charles Darwin's former home gently shades into the green hills, you can easily imagine the man himself stood on the same spot, inspired by the natural world around him.

Down House, pictured right, and its gardens have been lovingly restored since being acquired for the nation by English Heritage in 1996. Darwin would recognise every nook.

The birthplace of the theory of evolution is one of a tranche of places hoping to be eventually designated a world heritage site by the United Nations' cultural division, Unesco. Down House is one of the most deserving of the current contenders jostling for inclusion on a list which already includes the Taj Mahal, Sydney Opera House and Yosemite National Park. In the garden at Down, I meet Alister Hayes, the heritage co-ordinator for Bromley Council. He is so passionate about Down that he walks me round on his day off.

Hayes' enthusiasm for the house draws me into the story. As we explore the greenhouse – walking past rows of Venus flytraps of the same type Darwin fed his dinner to in the name of experimentation 160 years ago – Hayes explains: "Darwin went round the world thinking of questions, then he did experiments here on a local scale, and then the theories he developed had a global resonance. It was global, to local, to global. And that's a big reason why we believe this should be a world heritage site.

"Let me show you this!" Hayes says mischievously, and we wander down to the Sandwalk, a circular path where Darwin would stroll and think. The breeze is starting to whip in across the fields; there's a pleasing wildness despite the proximity of sprawling London. Hayes kicks a pile of stones and smiles broadly: "Darwin would do five circuits of the path every day while he was writing, and would move a stone after each lap. But his children loved to hide in the hedge and put the stones back in the pile – so their dad would sometimes walk around 6 or 7 times by mistake."

Darwin's brood were often roped in to help out with dad's experiments. That sense of the Darwin family having thrived here – in an uncommonly modern way – makes the place come alive. The very foundations of science and religion were rocked by the work Darwin meticulously did at Down. In the study, where Hayes says "Darwin became the scientist and writer we know", I marvel at the desk on which he wrote On the Origins of Species. As the biologist Richard Dawkins said of the book: "It meant humans no longer needed to believe in the supernatural."

The study – filled with trinkets and maps – is an inspiring room. In the bookcase sits an inscribed copy of Das Kapital, given to Darwin by Karl Marx in 1847.

Twice Britain has tried to get Down House – and the sinuous countryside, now dubbed "Darwin's Landscape Laboratory", that surrounds it – onto the list of world heritage sites. Twice the Unesco committee has stopped short of saying "yes". But hopes remain high that Down and Darwin will have their day.

The process of getting your site into this prestigious club is tricky: sites must meet specific criteria, and bid documents need to be produced by government bodies which argue why a potential site deserves inclusion. Petya Totcharova, Europe and North America chief of Unesco's world heritage centre, explains to me: "To be included, sites must be of outstanding universal value and meet at least one out of ten selection criteria." A site must basically be either an outstandingly beautiful slice of the natural world, or a building or town which has cultural, industrial or historical significance.

Totcharova goes on: "The criteria are regularly revised to reflect the evolution of the world heritage concept itself. We want to ensure the list reflects the world's cultural and natural diversity."

Since the programme began in 1972, 911 world heritage sites have been approved. Of these, 28 are in Britain, including Stonehenge and Ironbridge Gorge. Earlier this year a British committee overseen by the Department for Culture, Media and Sport (DCMS) considered a longlist of 38 possible places to put forward over the course of the next decade. Among those rejected from this longlist were Chester's Rows and Blackpool, historic York and Charles Rennie Mackintosh's Glasgow buildings.

A shortlist of 11 tentative sites was announced in March – including Creswell Crags in Derbyshire and Chatham Dockyard in Kent. A DCMS spokesman explains: "In drawing up the tentative list of 11, we have attempted to reflect the priorities of the world heritage committee to fill gaps and to address the imbalance of representation – for example of cultural landscapes, industrial archaeology and scientific achievement." But is there politicking? Is there any pressure to shortlist a range of sites spread across different regions of Britain?

"No, there are no quotas for different parts of the country or pre-judgments made. It's about each individual site, wherever that is, and whether it meets the Unesco criteria," says the DCMS spokesman.

From this list of 11, a maximum two nominations per year can be submitted to Unesco, but this year Britain hasn't submitted any. It's a long-term project, and we will have to wait until next summer for new British sites.

The recently shortlisted British Overseas Territory of St Helena, where Napoléon died in exile in 1821, is hopeful of eventual inclusion. "It's an amazing achievement to have made it onto the shortlist," Jamie Roberts, director of the St Helena National Trust (and the man who wrote their bid) tells me. "This remote Atlantic island is in decline – but the prospect of world heritage status gives us real hope that we can attract more visitors and secure our future. We get very little financial support from the British government, even though we're UK citizens and our heritage is distinctly British."

The next world heritage committee meets from 19-29 June in Paris. It will consider 40 sites for elevation – but none in Britain, this time. However, by the time of next year's congress, Britain will hopefully get a couple of new world heritage sites. One of the sites already nominated by the British government for the 2012 round are the twin monasteries of Monkwearmouth and Jarrow.

Matthew Havercroft, the editor of Heritage magazine says of the twin sites in the North-east: "The former home of Venerable Bede, widely regarded as the greatest of all the Anglo-Saxon scholars, they are seen as a masterpiece of craftsmanship and artistry. They're also 500 years older than the world heritage site of Fountains Abbey in the Yorkshire Dales, so have a good chance of getting the nod next year."

But will Down's turn come? Alister Hayes says: "I hope the committee will share our view that the bid is worthy not because a great scientist happened to live here, but because he undertook so much of his important scientific work here."

As the slow anti-intellectual creep of religious fundamentalism and creationism continues to threaten the values of science and modernism we've worked so hard for, perhaps now more than ever it's time to rubber stamp Darwin's great theory – and the part this pretty corner of Kent played in it. As Hayes puts it: "Darwin was observing the very struggle for existence on his back lawn. Isn't that worth recognising?"

The British contenders

'Heritage' magazine's Matthew Havercroft, rates the chances of five of the sites that are on the UK's shortlist for Unesco World Heritage status in 2012

1. Jodrell Bank Observatory

Manchester University's horticulture department changed forever when it became a site for star-gazing. The giant Lovell Telescope – used for listening to radio signals from space – was completed in 1957.

Mark Havercroft: "Top marks for first impressions and quirkiness, but is Jodrell too young to secure Heritage Status, putting it alongside the Egyptian pyramids, and the Great Wall of China?"

How likely to be selected eventually? 3/5

2. The Lake District

One of England's most popular tourist attractions. Wordsworth, Shelley and Beatrix Potter are just some of the folk who've fallen under the spell of the country's largest National Park.

MH: "With its stunning landscape and

literary links this would be the obvious winner. They awarded the entire city of Bath World Heritage Status in 1987 so there's no reason why a National Park couldn't follow suit."

How likely to be selected eventually? 5/5

3. Slate industry of North Wales

Centred on the Gwynedd towns of Llanberis and Blaenau Ffestiniog, this is an intriguing post-industrial underdog in the current tentative list. The spoil heaps and deep quarries are striking, and the slate the Welsh-speaking workers mined is found on roofs all over the world.

MH: "All the elements are here: the quarries are atmospheric and brooding and have shaped local life for centuries, while the slate is revered around the world. Both towns are accessible from a newly extended railway."

How likely to be selected eventually? 3/5

4. The Forth Bridge

An industrial wonder of the Victorian Age, The Forth Bridge in Fife claimed the lives of 57 men during its construction between 1883 and 1890. It's the crowning glory not just of the engineer's pen but of the navvies who built the rail network of 19th century Britain with brute force.

MH: "Suitably iconic and eminently

accessible. Not beyond the realms of possibility given that Pontcysyllte Aqueduct, a similarly impressive feat of engineering, designed by William Jessop and Thomas Telford in the 18th century, secured the award in 2009."

How likely to be selected eventually? 4/5

5. St Helena

Britain's second-oldest colony is fiendish to reach, and debate has raged about whether to spend £250m building an

airport. The most famous resident of this tiny volcanic outpost between Africa and Brazil was the vanquished Napoleon, exiled here from 1815 until his death.

MH: "Accessibility is a big issue here as very few people are going to be able to appreciate it until they get around to building that airport. Sure to be a big barrier in the eyes of the Unesco judging panel."

How likely to be selected eventually? 2/5