By 1000 BCE, Peruvian cotton bolls were indistinguishable from modern cultivars of "G. barbadense". Native Americans grew cotton widely throughout South America and in the West Indies, where Christopher Columbus encountered it. The advent of worldwide trade resulted in many kinds of plants being introduced to new places (see Columbian exchange). In the case of cotton, this exchange happened in all directions, new world cottons to the old world, old world cottons to the new word, and cottons to places which they had never grown before. In some cases, this resulted in multiple kinds of cotton growing in the same region. Since then, most of these regions have transitioned to specialize in a particular kind of cotton, resulting in the distinctive market classes of today.