itself in time, place, and circumstances." By the early 1400s, European shipbuilding had begun to produce vessels able to travel long distances carrying substantial cargoes. Navigation was being transformed from an art (or sometimes simply good guesswork) into a science, and explorers were beginning to develop accurate charts, maps, and navigational equipment, allowing those ships to find their way home again with some assurance.
These advances allowed the concept of trade itself to expand from the act of exchanging goods and services with others in the immediate neighborhood to the notion of creating goods for export in order to secure products unavailable within a few days' ride. Europeans started to develop a taste for spices grown only in warmer climates, woods and gems and metals from distant shores, and other kinds of exotic merchandise. As explorers discovered new lands and reliable ways of getting to them, settlers and traders moved in, and one of the necessities for colonization, especially in the vast lands of the Americas, was a large quantity of cheap human labor to help clear fields, build houses, and cultivate the land.
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