Modern Angola was populated predominantly by nomadic Khoi and San peoples prior to the first Bantu migrations. The Khoi and San peoples were hunter-gatherers, rather than practicing pastoralism or cultivation of crops.[17] In the first millennium BC, they were displaced by Bantu peoples arriving from the north, most of whom likely originated in what is today northwestern Nigeria and southern Niger.[18] Bantu speakers introduced the cultivation of bananas and taro, as well as maintenance of large cattle herds, to Angola's central highlands and the Luanda plain. Due to a number of inhibiting geographic factors throughout the territory of Angola, namely harshly traversable land, hot/humid climate, and a plethora of deadly diseases, intermingling of pre-colonial tribes in Angola had been rare.[citation needed] After settlement of the migrants, a number of political entities developed. The best-known of these was the Kingdom of Kongo, based in Angola. It extended northward to what are now the Democratic Republic of the Congo, the Republic of the Congo, and Gabon. It established trade routes with other city-states and civilisations up and down the coast of southwestern and western Africa. Its traders even reached Great Zimbabwe and the Mutapa Empire, although the kingdom engaged in little or no trans-oceanic trade.[19] To its south lay the Kingdom of Ndongo, from which the area of the later Portuguese colony was sometimes known as Dongo. Next to that was the Kingdom of Matamba.[20] The lesser Kingdom of Kakongo to the north was later a vassal of the Kingdom of Kongo. The people in all of these states spoke Kikongo as a common language. Portuguese colonization[edit] Main articles: Colonial history of Angola and Portuguese Angola Coat of arms granted to King Afonso I of Kongo by King Manuel I of Portugal Portuguese explorer Diogo Cão reached the area in 1484.[20] The previous year, the Portuguese had established relations with the Kingdom of Kongo, which stretched at the time from modern Gabon in the north to the Kwanza River in the south. The Portuguese established their primary early trading post at Soyo, which is now the northernmost city in Angola apart from the Cabinda exclave. Paulo Dias de Novais founded São Paulo de Loanda (Luanda) in 1575 with a hundred families of settlers and four hundred soldiers. Benguela was fortified in 1587 and became a township in 1617. An authoritarian state, the Kingdom of Kongo was highly centralised around its monarch and controlled neighbouring states as vassals. It had a strong economy, based on the industries of copper, ivory, salt, hides, and, to a lesser extent, slaves.[21] The transition from a feudal system of slavery to a capitalist one with Portugal would prove crucial to the history of the Kingdom of Kongo.[22] As relations between Kongo and Portugal grew in the early 16th century, trade between the kingdoms also increased. Most of the trade was in palm cloth, copper, and ivory, but also increasing numbers of slaves.[22] Kongo exported few slaves, and its slave market had remained internal. But, following the development of a successful sugar-growing colony after Portuguese settlement of São Tomé, Kongo became a major source of slaves for the island's traders and plantations. Correspondence by King Afonso documents the purchase and sale of slaves within the country. His accounts also detail which slaves captured in war were given or sold to Portuguese merchants.[23] Afonso continued to expand the kingdom of Kongo into the 1540s, expanding its borders to the south and east. The expansion of Kongo's population, coupled with Afonso's earlier religious reforms, allowed the ruler to centralize power in his capital and increase the power of the monarchy. He also established a royal monopoly on some trade.[23][22] To govern the growing slave trade, Afonso and several Portuguese kings claimed a joint monopoly on the external slave trade.[23][22] The slave trade increasingly became Kongo's primary, and arguably sole, economic sector. A major obstacle for the Kingdom of Kongo was that slaves were the only commodity for which the European powers were willing to trade. Kongo lacked an effective international currency. Kongolese nobles could buy slaves with the national currency of nzimbu shells, which could be traded for slaves. These could be sold to gain international currency. As the slave trade was the only commodity in which Europeans were interested in the region during the 16th and 17th centuries, the Kongo economy was unable to diversify or later industrialise outside of sectors in which slavery was involved, such as the arms industry.[24][25] The increased production and sale of guns within the kingdom was due to the salient issue of the slave trade, which had become an increasingly violent struggle. There was a constant need for slaves for the kings and queens to sell in exchange for foreign commodities, the absence of which would prevent them from having any influence with European powers such as Portugal and eventually the Dutch Republic. Kongolese kings needed this influence to garner support from European powers for quelling internal rebellions. The situation became increasingly complicated during the rule of Garcia II, who needed the assistance of the Dutch military to drive out the Portuguese from Luanda, in spite of the fact that Portugal was Kongo's primary slave trading partner.[24] By the early 17th century, the supply of foreign slaves captured by the Kongolese externally was waning. The government began to approve the enslavement of freeborn Kongolese citizens for relatively minor infractions, nearly any disobeying of the authoritarian system and the aristocracy. If several villagers were deemed guilty of a crime, it became relatively common for the whole village to be enslaved. The resulting chaos and internal conflict from Garcia II's reign would lead into that of his son and successor, António I. He was killed in 1665 by Portuguese at the Battle of Mbwila 1665, together with a substantial proportion of the aristocracy. The colonists were expanding their power.[26] War broke out more widely in the Kingdom of Kongo after the death of António I.[25] Much of the stability and access to iron ore and charcoal necessary for gunsmiths to maintain the arms industry was disrupted. From then on, in this period almost every Kongolese citizen was in danger of being enslaved.[27][24] Many Kongolese subjects were adroit in making guns, and they were enslaved to have their skills available to colonists in the New World, where they worked as blacksmiths, ironworkers, and charcoal makers.[25] The Portuguese established several other settlements, forts and trading posts along the Angolan coast, principally trading in Angolan slaves for plantations. Local slave dealers provided a large number of slaves for the Portuguese Empire,[28] usually in exchange for manufactured goods from Europe.[29][30] This part of the Atlantic slave trade continued until after Brazil's independence in the 1820s.[31] Queen Ana de Sousa of Ndongo meeting with the Portuguese, 1657 Depiction of Luanda from 1755 Despite Portugal's territorial claims in Angola, its control over much of the country's vast interior was minimal.[20] In the 16th century Portugal gained control of the coast through a series of treaties and wars. Life for European colonists was difficult and progress was slow. John Iliffe notes that "Portuguese records of Angola from the 16th century show that a great famine occurred on average every seventy years; accompanied by epidemic disease, it might kill one-third or one-half of the population, destroying the demographic growth of a generation and forcing colonists back into the river valleys".[32] During the Portuguese Restoration War, the Dutch West India Company occupied the principal settlement of Luanda in 1641, using alliances with local peoples to carry out attacks against Portuguese holdings elsewhere.[31] A fleet under Salvador de Sá retook Luanda in 1648; reconquest of the rest of the territory was completed by 1650. New treaties with the