European expansion had multiple causes. The first was economic. By the middle of the fifteenth century Europe was experiencing a revival of population and economic activity after the lows of the Black Death. This revival created renewed demand for luxuries, especially spices, from the East. The fall of Constantinople and the subsequent Ottoman control of trade routes created obstacles to fulfilling these demands. European merchants and rulers eager for the profits of trade thus needed to find new sources of precious metal to exchange with the Ottomans or trade routes that bypassed the Ottomans.

Why were spices so desirable? Introduced into western Europe by the Crusaders in the twelfth century, pepper, nutmeg, ginger, mace, cinnamon, and cloves added flavor and variety to the monotonous European diet. Not only did spices serve as flavorings for food, but they were also used in anointing oil and as incense for religious rituals, and as perfumes, medicines, and dyes in daily life. Apart from their utility, the expense and exotic origins of spices meant that they were a high-status good, which European elites could use to demonstrate their social standing.

Religious fervor and the crusading spirit were another important catalyst for expansion. Just seven months separated Isabella and Ferdinand's conquest of the emirate of Granada, the last remaining Muslim state on the Iberian Peninsula, and Columbus's departure across the Atlantic. Overseas exploration thus transferred the militaristic religious fervor of the reconquista (reconquest) to new non-Christian territories. As they conquered indigenous empires, Iberians brought the attitudes and administrative practices developed during the reconquista to the Americas. Conquistadors fully expected to be rewarded with land, titles, and power over conquered peoples, just as the leaders of the reconquista had been.

A third motivation was the dynamic spirit of the Renaissance. Like other men of the Renaissance era, explorers sought to win glory for their amazing exploits and demonstrated a genuine interest in learning more about unknown waters. Scholars have frequently described the European discoveries as an outcome of Renaissance curiosity about the physical universe. The detailed journals kept by European voyagers attest to their fascination with the new peoples and places they visited.

Individual explorers often manifested all of these desires at once. Columbus, a devout Christian, aimed to discover new territories where Christianity could be spread while seeking a direct trade route to Asia. The motives of Portuguese explorer Bartholomew Diaz were, in his own words, “to serve God and His Majesty, to give light to those who were in darkness and to grow rich as all men desire to do.” When the Portuguese explorer Vasco da Gama reached the port of Calicut, India, in 1498 and a native asked what he wanted, he replied, “Christians and spices.”4 The bluntest of the Spanish conquistadors (kahn-KEES-tuh-dawrz), or conquerors, Hernán Cortés, announced as he prepared to conquer Mexico, “I have come to win gold, not to plow the fields like a peasant.”5

Ordinary seamen joined these voyages to escape poverty at home, to continue a family trade, or to win a few crumbs of the great riches of empire. Common sailors were ill-paid, and life at sea meant danger, unbearable stench, hunger, and overcrowding. For months at a time, 100 to 120 people lived and worked in a space of 1,600 to 2,000 square feet.

The people who stayed at home had a powerful impact on the voyages of discovery. Merchants provided the capital for many early voyages and had a strong say in their course. To gain authorization and financial support for their expeditions, they sought official sponsorship from the Crown. Competition among European monarchs for the prestige and profit of overseas exploration thus constituted another crucial factor in encouraging the steady stream of expeditions that began in the late fifteenth century.

The small number of Europeans who could read provided a rapt audience for tales of fantastic places and unknown peoples. Cosmography, natural history, and geography aroused enormous interest among educated people in the fifteenth and sixteenth centuries. One of the most popular books of the time was the fourteenth-century text The Travels of Sir John Mandeville, which purported to be a firsthand account of the author's travels in the Middle East, India, and China. Although we now know they were fictional, these fantastic tales of cannibals, one-eyed giants, men with the heads of dogs, and other marvels were believed for centuries. Columbus took a copy of Mandeville and the equally popular and more reliable The Travels of Marco Polo on his voyage in 1492.