When young Charles Darwin first landed in the Galapagos Islands in 1835 he was so disappointed by what he saw he is said to have considered re-boarding the HMS Beagle and hightailing it out of there.
The 26-year-old Darwin expected this small group of islands on the equator to be a lush tropical paradise teeming with wildlife, but what he encountered was barren, harsh and windswept. Not particularly inviting, even after months of debilitating sea sickness aboard the Beagle.
And landing at Baltra airport after an hour-and-a-half flight from Ecuador it's not hard to see how Darwin felt. This hot, windy, monochromatic place looks more like the Australian Outback than a tropical paradise. Luckily Darwin persevered, or he may never have come up with his theory of evolution.
Ever since, this intriguing land of few humans but many weird and wonderful animal species has attracted explorers and tourists.
Sea lions wander up to you on the beach like curious labradors and play with you when you're snorkelling. Marine iguanas don't flinch when you step over them, and giant tortoises lazily eye you as you meander by.
There are no predators in the Galapagos Islands, apart from the not-very-scary endemic hawk, so the animals evolved without the fear that most animals possess.
Marine iguanas of about 1m cover the rocks among the moon-like lava formations of Bartolome Island. These dragon-like creatures bask in the sun to warm up after their forays into the ocean and every so often noisily sneeze salt.
On nearby Rabida Island, the sand is a deep red - you could be on Mars, if it wasn't for the sea lions lolling on every inch of the beach.
On Espanola Island, more sea lions bask on the long, white sand beach. And up in the highlands you have to be careful not to trip over all kinds of strange birds, from nesting albatrosses to blue-footed boobies carrying out their curious mating dance.
How so many animals different from anything anywhere else in the world could end up on this isolated group of islands barely touched by humans is a puzzle. It certainly puzzled Darwin, but it planted the seed for what would become his theory of evolution. It wasn't until he was back in London studying the samples he had collected in Galapagos that it occurred to Darwin that living organisms adapt and modify until they become different species. In the Galapagos, the isolation is such that different subspecies developed on each island. There are, for example, 13 types of finch, each slightly but crucially different to the next.
After a quick boat ride across the channel to Santa Cruz, where most of the Galapagos' human inhabitants live, a bus ride to the island's centre shows how varied these islands can be. After 15 minutes or so along a road bordering barren terrain, the temperature suddenly drops and, almost incredibly, it starts to rain. The landscape turns from dry rocky plains into lush vegetation.
Apparently, we've just left the rain shadow, an area from which rain-producing weather systems are blocked by mountains.
However, we are here during the dry season, so for most of our trip it's dry, windy and warm.
The hot season is from December to May, when temperatures average 26C to 30C and the days are humid.When the trade winds arrive is causing major worries as to whether the ecology can handle the strain.The Galapagos presents a once-in-a-life-time tourism experience, but humans have the potential to devastate the ecology.Marine iguanas are a common sight.Land iguanas don't move for anybody.A blue-footed booby prepares to go through its routine.the temperature drops to a pleasant 23C to 26C.
The quirk of nature that is the Galapagos presents a once-in-a-life-time tourism experience, but humans have the potential to devastate the ecology. From as early as the 1600s, visiting seafarers, often starving after long ocean voyages, found a cornucopia of wildlife that put up little resistance to hunting.
About 200,000 of the islands' enormous tortoises, a long-lasting source of protein because they could be carried alive on ships, were taken, mainly by whalers, in the 1700s.
A subspecies of giant tortoise developed on 12 islands, each with subtle differences in the shape of the shell. One of these subspecies, on the island of La Pinta, has only a sole survivor - the famous Lonesome George, who can be visited at the Charles Darwin Research Centre on Santa Cruz.
And with humans came the introduction of alien species. Farm and domestic animals, rats and insects have all posed threats to this delicate ecosystem. Goats have been particularly devastating, stripping entire islands of vegetation and wiping out plant species. But a successful eradication programme on Santiago Island, carried out by a group of New Zealand "goat busters" specially selected for their shooting-from-helicopter skills, cleared the island of 100,000 goats.
The mosquito is the latest threat.
An endemic Galapagos mosquito carried no diseases, but the influx of visitors from the mainland means other breeds are getting in, despite tough biosecurity measures such as spraying all arriving planes.
If malaria was introduced to the Galapagos it could be devastating for the native species.
When tourism to the islands began in earnest in the late 1960s, about 2000 visitors came every year. Now more than 100,000 tourists visit each year and there is a permanent population of 24,000, mostly mainland Ecuadorians working in tourism.
Despite regulations and restrictions on visitor numbers, there are major concerns as to whether the fragile islands can cope.
Alice Neville travelled to the Galapagos Islands with assistance from LAN Airlines and World Journeys.