What Was the Age of Exploration? How Europe Mapped the World and Changed It

The voyages were driven by trade. Spices, silk and other Asian goods reached Europe through a chain of Muslim and Italian middlemen, each taking a margin, and a direct sea route would cut them all out. The tools were in place: the compass, from China; the astrolabe and tables for finding latitude from the sun, from Arab astronomers; the caravel, a small, nimble ship with triangular sails that could beat into the wind; and printed maps and accounts of earlier travellers, including Marco Polo, which circulated widely after 1450. Gunpowder weapons gave small crews an advantage over anyone they met.

Portugal went first because it faced the Atlantic, had nowhere else to expand, and had a prince, Henry, called the Navigator, who spent forty years from about 1420 sponsoring voyages down the African coast, each one going a little further. Spain followed once it had finished the conquest of Granada in 1492.

The key journeys came in a rush around the turn of the sixteenth century:

• •1488: Bartolomeu Dias rounds the Cape of Good Hope, proving the Atlantic and Indian Oceans connect
• •1492: Christopher Columbus, seeking Asia by sailing west for Spain, reaches the Caribbean and never accepts it is not Asia
• •1498: Vasco da Gama reaches India by sea, and Portugal begins building a trading empire from Africa to Malacca
• •1500: Pedro Cabral, blown off course to India, lands in Brazil
• •1519 to 1522: Ferdinand Magellan's expedition crosses the Pacific; Magellan is killed in the Philippines and one ship of five returns, completing the first circumnavigation
• •1519 to 1533: Cortes and Pizarro conquer the Aztec and Inca empires with small forces, local allies and epidemic disease

In 1494, two years after Columbus, Spain and Portugal agreed at Tordesillas to split all newly found lands along a line 370 leagues west of the Cape Verde Islands: Portugal took everything east, Spain everything west. Nobody else was consulted, and the line, when it was extended round the globe, gave Portugal Brazil and Spain the Philippines. The treaty is why Brazil speaks Portuguese and the rest of South America Spanish, and it was ignored by the English, French and Dutch, who began their own voyages in the sixteenth century and their own colonies in the seventeenth.

The lasting consequence was biological. The historian Alfred Crosby named it the Columbian Exchange: for the first time since the continents separated, the plants, animals and microbes of the Old World and the New moved between them. Maize, potatoes, tomatoes, chillies, cacao, tobacco and cassava went east and transformed farming from Ireland to China; wheat, sugar, coffee, horses, cattle, pigs and sheep went west and transformed the Americas. The potato alone allowed Europe's population to grow as it had never done, and maize did the same for parts of Africa and China.

The microbes went mainly one way. The peoples of the Americas had no exposure to smallpox, measles, influenza or typhus, and within a century of contact their population had fallen by something like ninety percent, the largest demographic catastrophe on record, which is the main reason a few hundred Spaniards could take empires of millions. Syphilis appears to have travelled the other way. Sugar plantations in the emptied lands needed labour, and the Atlantic slave trade, which carried some twelve million Africans across the ocean over the following three centuries, was the direct result.

For most of the last five hundred years the voyages were told as a story of daring and discovery, and the word discovery itself has become contested, since the lands had been inhabited for tens of thousands of years and the Americas had been reached by Norse sailors around 1000. The older histories were not wrong about the daring: Magellan's crew ate rats and leather in the Pacific, and most of the men on most of the voyages did not come back. They were silent about the cost, which fell on people who had not asked to be found. Both halves are the history, and the honest account holds them together: the same two centuries connected the world and emptied a hemisphere.

The Age of Exploration was the period from about 1400 to 1600 in which Portuguese and Spanish ships, driven by the spice trade and equipped with the compass, the caravel and gunpowder, found sea routes around Africa to Asia, reached the Americas and circled the globe. It joined the hemispheres in the Columbian Exchange of crops and animals, and through disease, conquest and the slave trade it remade the populations of three continents.