It has become a convention of books about exploration to explain dolefully that there is nothing left to find. All that remains, we are told, are the self-professed "explorers", forced into attention-grabbing japes - ballooning across the Arctic or running naked through the Sahara - in the absence of a proper unknown to discover. This certainly appears to be the conclusion of Felipe Fernández-Armesto's comprehensively anti-hagiographic survey, Pathfinders: a global history of exploration. He suggests that the very title of his work refers to an obsolete breed: "the main historic work of pathfinding and mapping is over . . . Even the genuinely unknown is predictable: staked out by cameras and radio telescopes ahead of the spacemen or divers."
The path to this dubious pinnacle has been, he writes, a "march of folly, in which almost every step forward has been the failed outcome of an attempted leap ahead". His cast of explorers is a motley bunch: "oddballs or eccentrics or visionaries or romancers or social climbers or social outcasts . . . with enough distortion of vision to be able to reimagine reality." The legions of explorers, pressing on through hostile tracts of jungle, desert or ice, were often inspired by venerable myths and yarns, or unscrupulously evoked them to screw money out of their backers: the myth of a vast region in the southern hemisphere, Terra Australis, or the dream of a north-west passage, or the idea that there was clear water at the North and South Poles. The reality, however, was often far from Utopian, as explorers through the ages amassed an appalling "tally of atrocities, despoliation, expropriation and abuse".
Fernández-Armesto applies a stern gaze to various explorer legends: Christopher Columbus, who passed the time "bloodily imposing obedience on every native community he could track down"; Vasco da Gama, "an irascible provincial", a "xenophobe improperly transplanted to the tropics", "trying to enhance commerce by bloodshed"; John Barrow, "irascible, ungenerous and usually wrong-headed"; and Robert Scott, "an irresponsible commander" whose "British form of sentimentality perverted his judgement".
Broadly, Fernández-Armesto seems to be with Diderot, who denounced explorers as agents of barbarism, driven merely by "tyranny, crime, ambition, misery". His portraits are crisp and eloquent, written in consistently memorable prose, though this economy of treatment prevents him from producing any real shocks or revelations. His explorers are seen from a distance, however fine his turn of phrase, and few readers will be stunned to hear that the New World explorers proceeded with appalling violence, or that many Victorian polar explorers were stolid and arrogant.
Yet the temporal remit of Fernández-Armesto's book is wonderfully broad - from 150,000 years ago to the present day, via the "mitochondrial Eve" and sundry other diversions - and the geographical remit encompasses Asia, the Americas, the Arctic and Antarctic, Africa, Australia and a few other places besides. He sustains a chronological structure, which involves whirling from one location to another within a particular century, then whirling around the globe again for the next century. The shifts are unashamedly marked - no sooner have we despatched Scott to the freezing polar winds than we are chasing pygmies with Henry Morton Stanley in Africa. This has a rather brilliant accumulative effect - dramatising the meandering, haphazard process by which the globe has been mapped, the bizarre coincidences and sudden leaps forward. It builds into a meticulously researched account of centuries of ambition and world-spanning lunacy.
At the end of all these myths and wild acts, these tales of monomaniacs and criminals, the author asks: "What remains?" While mourning the death of the conventional idea of the unknown, he also argues that there are vast realms still undiscovered, if we only care to notice them. "Evolution never stops. Species emerge and die out; cultures change unrecognisably. Climate change never ceases. Ecosystems are constantly self-reformed."
And then there are the heights and depths: the lowest reaches of the ocean, the chasms beneath the earth's crust, the upper atmosphere. Fernández-Armesto's thoughtful adjustment to the usual lament is his suggestion that the emphasis on blank spaces, on planting national flags in new patches of ground, has clouded the issue - our clichés of exploration blind us to the real frontiers of our world, the great gaps still remaining in our knowledge. The question for Fernández-Armesto is whether we are ultimately too ridiculous and myopic to notice the riches around us.
He ends with sombre humour, discussing space exploration via Monty Python - "Let us hope . . . that intelligent life exists out there, because 'there's bugger all down here' on dear old Earth."
Joanna Kavenna is the author of "The Ice Museum: in search of the lost land of Thule" (Penguin)