Although the Canary Islands were known to the mariners of the ancient world, it took till the fifteenth century for the Europeans to re-discover them, as a part of the sudden outpouring of oceanic voyages stemming from technological developments in ocean going vessels which eventually culminated in Christopher Columbus' discovery of the Americas and Vasco da Gama's discovery of a route round Africa to India. They were peopled by a 'primitive stone age' people called the Guanches who probably arrived from the coast of Northern Africa in pre-historic times, although by the arrival of the Spanish they had lost all knowledge of sailing. The conquest of the Canary Islands began in 1402 and the Guanches were quickly exterminated by the Spanish through both fighting and disease. As such there is very little historical information on them although some writings extant today refer to them as being tall and blond. As the Guanches disappeared the islands were settled by the Spanish people, mainly of Andalusian origin. This has effected the agriculture and the dialect of the Islanders, which is principally Andalusian. Until the growth of tourism, the inhabitants subsisted primarily on agriculture with the profitable crops historically changing with demand from tobacco to sugar to tomatoes and currently bananas, and fishing and they also serviced the profitable Spain to South America trade routes supplying slaves and stopover points. As the Canary Islands were open to attacks by the pirates in the Atlantic Ocean many of the villages were built upon inaccessible rocky outcrops, with access to the sea. This can make for exciting cycling along high and narrow roads.