Material World: The Six Raw Materials That Shape Modern Civilization

by Ed Conway

For most of our existence the only way of fixing nitrogen from the atmosphere was to hope for a lightning strike or to wait months for the bacteria in certain plants to do it. Saltpetre represented a valuable shortcut, as did manures and compost, both of which are rich in nitrogen, albeit less rich than the fossilised bird droppings of the Chincha Islands. For years the Incas had collected this smelly earth—huanu as they called it—and ground it into a dust they sprinkled on to their fields. In recognition of the miracle they made the Chinchas holy islands, where killing a bird was a capital offence. When the Spanish conquistadores arrived and laid waste to what is now Peru, they paid surprisingly little attention to guano, as it became known, even though it was viewed by the Incas as being as precious as gold. But when the British