QI The Book of the Dead

Humboldt ‘the true discoverer’ of the continent. Before him no one had guessed that the Amazonrain forest was the planet’s richest and most diverse habitat. With Bonpland he collected over 60,000 samples and discovered over 3,500 new species: no single trip has ever yielded as many. Humboldt’s vision went far beyond the work of his contemporaries, who were busily filling in branches on the sprouting tree of species devised by Linnaeus. He was intent on uncovering the hidden connections between apparently unconnected phenomena. He wasn’t just interested in what a plant looked like. He wanted to know why it lived where it lived, the type of rocks that produced the soil it grew in, the prevailing climatic conditions, the other species that grew near it – as well as the species that fed on it, near it, or under it and how the whole ecological cycle it was part of worked. That was why he had to travel. It was not enough to give his samples a label and a Latin name: he had to understand the context. One of the pleasures of reading Humboldt is that he never lost his childlike sense of awe: ‘The stars as they sparkle in the firmament fill us with delight and ecstasy,’ he wrote, ‘and yet they all move in orbit marked out with mathematical precision.’
    Humboldt was incapable of noticing anything without then asking ‘why?’ When he observed the ‘brilliant fireworks’ of the Leonid meteor shower in northern Venezuela, he went on to calculate when they would next return. Confronted with volcanoes, he perceived that they were lined up along subterranean fissures in the earth’s crust and was able to demonstrate the course of those faults. He proved that many mountain ranges were volcanic in origin, destroying the then fashionable theory of Neptunism, which suggested that all rocks were originally oceanic sediments. He was the first to show that the earth’s magnetic field weakens as you travel from the poles towards theequator. He covered so much ground he was able to plot lines linking places with same temperature to map the planet’s climate, for which he coined the word ‘isotherm’. His discovery of the guano deposits on the Peruvian coast revolutionised agriculture in Europe and America, providing entrepreneurs with a lucrative and potent source of fertiliser.
    His scientific curiosity extended to human culture, too. In South America he saw that the continent’s startling range of plant and animal species was mirrored by its ethnic diversity: ‘A traveller, however great his talent for languages, can never hope to learn enough to make himself understood along the navigable rivers.’ On the Orinoco he found a parrot that was the last remaining speaker of a language belonging to a tribe exterminated by its neighbours, and dutifully recorded the bird’s forty-word vocabulary. Aztec and Inca ruins led him to suggest, heretically for his time, that their cultures had once rivalled the ancient civilisations of Europe and the Middle East – and he was the first to speculate that the native peoples of South America had originally come from Asia, a hypothesis now confirmed by genetics. Wherever Humboldt looked, new possibilities emerged.
    He was a remarkably hands-on scientist. While still a mining inspector back in Bavaria, his fascination with Luigi Galvani’s theories of animal magnetism had led him to conduct over 4,000 experiments, many on himself, in which he attached electrodes to his skin and recorded the sometimes excruciating pain they caused. In South America he and Bonpland climbed to 19,260 feet (5,870 metres) on Chimborazo, the Ecuadorian volcano then thought to be the world’s highest mountain. Although they didn’t quite make the summit, no one had ever climbed so high before. Humboldt, his nose streaming blood, became the first person tonote down the effects (and correctly guess the cause) of altitude sickness. In the jungle he reported being unable to breathe because of the dense clouds of mosquitoes. Seeing how the Orinoco Indians prepared curare, a poison from plants, he tested it on himself then on captured monkeys, giving them gradated doses and even resorting to mouth-to-mouth resuscitation to keep them alive. To penetrate the mystery of electric eels, he ‘imprudently’ placed both his bare feet on one (‘the pain and the numbness are so violent it is impossible to describe the nature of the feeling they excite’) and then asked the Indians how to collect specimens