Ranching was developed by European settlers in the arid regions of America and Australia, and from there was transferred to other parts of the world (for example South Africa). The roots probably lie in summer-dry Iberia, where in the course of the Reconquista deserted, semi-arid areas were used by large herds of merino sheep and cattle under the supervision of mounted shepherds. This agricultural system found its way into the deserted grasslands of the Americas with the Spanish-Portuguese conquest in the 16th century: the pampas, the Gran Chaco, the sertãos of Brazil, the llanos of Venezuela, the drylands of northern Mexico, Texas' and California. The fencing of vast areas with barbed wire was deliberately promoted in the late 19th century to protect the herds from predators and to manage them better, but also to mark and enforce the ranchers' claims to ownership over indigenous peoples (for example, Prairie Indians in the USA, San in Southwest Africa or Aborigines in Australia). Until the beginning of the 20th century, the orientation towards the world market increased, but decreased thereafter: In South America in favor of supplying the rapidly growing cities in the individual states, and in the industrialized countries primarily through the political protection of national agriculture from foreign competition (agricultural protectionism).