Chili peppers have been a part of the human diet in the Americas since about 7500 BC. They were domesticated there between 5200 and 3400 BC, one of the first cultivated crops in the Americas. Chili peppers are thought to have been domesticated at least five times by prehistoric peoples in different parts of South, Central and North America, from Peru in the south to Mexico in the north and parts of Colorado and New Mexico (Ancient Pueblo Peoples).
Christopher Columbus was one of the first Europeans to encounter them (in the Caribbean), and called them "peppers" because of their similarity in taste (though not in appearance) with the Old World peppers of the Piper genus. Columbus was keen to prove (incorrectly) that he had in fact opened a new direct nautical route to Asia, contrary to reality and the expert consensus of the time, and it has been speculated that he was therefore inclined to denote these new substances "pepper" in order to associate them with the known Asian spice.
Diego Álvarez Chanca, a physician on Columbus' second voyage to the West Indies in 1493, brought the first chili peppers to Spain, and first wrote about their medicinal effects in 1494.
From Mexico, at the time the Spanish colony that controlled commerce with Asia, chili peppers spread rapidly into the Philippines and then to India, China, Korea and Japan with the aid of European sailors. The new spice was quickly incorporated into the local cuisines.
An alternate sequence for chili pepper's spread has the Portuguese picking up the pepper from Spain, and thence to India, as described by Lizzie Collingham in her book Curry. The evidence provided is that the chili pepper figures heavily in the cuisine of the Goan region of India, which was the site of a Portuguese colony (e.g. Vindaloo, an Indian interpretation of a Portuguese dish). Collingham also describes the journey of chili peppers from India, through Central Asia and Turkey, to Hungary, where it became the national spice in the form of paprika.