Evolution's Workshop by Edward J Larson

A voyage to the reptile heaven that inspired Darwin

The Galapagos archipelago lies in the Pacific Ocean, about 600 miles west of Ecuador. The islands are home to some of the world's rarest species, including giant tortoises and unusual birds like the blue-footed booby. Humans first visited the islands nearly 500 years ago, when the Spanish government sent the Bishop of Panama to investigate the Pacific coast as far as Peru, but they became famous in the 19th century when Charles Darwin stopped there. Darwin's account of his visit, travelling as a naturalist on the Pacific survey ship HMS Beagle, made a charming chapter in his journal of the voyage.

Delighting in teasing the tame animals, Darwin rode on the back of a giant tortoise and pulled the tails of land iguanas; he threw them into the sea to prove they disliked water, and cut open their stomachs to establish what they ate. The novelist Herman Melville, who arrived there in 1841, six years after Darwin, was neither as curious nor as scientific in his approach. "Man and wolf alike disown them," he wrote melodramatically. "Little but reptile life is here found. No voice, no low, no howl is heard; the chief sound of life here is a hiss."

It was only in 1859, however, when Darwin published On the Origin of Species, that the archipelago attained its almost mythic status in the intellectual shift from creationism to the theory of evolution. Darwin summed up its impact on his thinking in a succinct passage describing how his visit in 1835 brought him "near to the very act of creation. I often asked myself how these many peculiar animals and plants had been produced: the simplest answer seemed to be that the inhabitants of the several islands had descended from each other, undergoing modification in the course of their descent; and that all the inhabitants of the archipelago were descended from those of the nearest land, namely America."

The impact of this realisation was, in the middle of the 19th century, explosive. Natural history was still influenced by John Ray's assertion that everything in the world had been created by a Supreme Being on the first day and remained in the same pristine condition. Darwin shattered that myth, although his opponents spent the rest of the century trying to disprove him. According to the biologist Julian Huxley, Darwin's trip to the Galapagos was "the first step out of the fairyland of creationism into the coherent and comprehensible world of modern biology".

It also brought the mixed blessing of intense scientific curiosity to the islands, which is one of the stories Edward J Larson tells in this intelligent and readable book. Larson is a professor of history and law, and he handles complex scientific controversies and the islands' frequently tragic story with clarity and confidence. For every person who went to the Galapagos to follow reverently in Darwin's footsteps, someone else turned up to make what they could, removing huge numbers of animals and introducing alien species – cats, dogs, goats – that ravaged the habitat of indigenous fauna.

The gentle giant tortoise was almost wiped up, not just by whalers but museums and collectors whose demands for specimens were insatiable. A photograph shows scientists from the California Academy of Scientists hauling a dead tortoise to their ship during a 1905-6 expedition; another shows 250 specimens stored in a ruined museum in San Francisco after the 1906 earthquake.

It was because of this history of human predation that Ecuador declared the islands a national park in 1959, inviting British planners to advise. Since then, visitor numbers have increased, rising to 40,000 each year by 1990, and bringing more problems in their wake. Earlier this year, an oil tanker supplying tourist ships foundered off one of the biggest islands, San Cristobal, and disaster was averted only when strong winds washed the slick out to sea. When I flew to San Cristobal in April, the wreck could be seen offshore, jutting menacingly out of the sea.

Yet conservationists argue, with some justice, that strictly controlled tourism is the only way to protect the islands. And the story is not all gloom and doom: the Charles Darwin Station on Santa Cruz island has set up a successful breeding programme to repopulate the archipelago with giant tortoises, for instance. Visitors are allowed to walk on cliffs among albatross nests, gazing in astonishment at the floppy chicks almost as large as their parents; they can sail in submerged volcanic craters and watch sea-lions sunbathe. As Larson concludes in a dramatic narrative that begins with pirates and ends with eco-tourists, nothing has managed to spoil the Galapagos islands as "a place of profound wonder".