According to archaeological records, South American civilization began around 10,000 BC, when the first settlers from North and Central America arrived. They settled in Tierra del Fuego, Argentina, southern Chile, the south-central plains of the Grand Canyon region, and parts of the Central Andes Mountains. Their groups are based on kinship and rank by sex and age. These nomadic groups were later replaced by highly agricultural societies. Agrarian societies are located in the Arawak coast and inland forest areas of Brazil and the Greater Antilles. They were able to maintain large and stable social units because of the abundance of food. Other peoples who settled in the Caribbean and northern Andes developed more complex forms of social organization based on military and religious rituals, supported by agricultural techniques. The indigenous cultures of South America took root in the central Andean Mountains around 2300 BC and developed rapidly, both farming and technology, for thousands of years. Around 1000 AD, there were the kingdoms of Chimu, Tiwanaku and later the Inca Empire. Inca prosperity waned until the Spanish invasion in the 16th century. Its territory stretches from Peru to northern Chile, and it has developed effective irrigation systems and sophisticated systems for controlling food production, storage and distribution. The population peaked at 3.5 million. Its social classes were divided into hereditary royalty, nobility, artisans and peasants. The most remarkable innovation of Inca civilization was the substitution of law for custom in shaping social organization and the attainment of high artistic standards. The European conquest of South America in the 16th century completely replaced the agricultural and political practices of the Inca Empire with those of the Spanish, and the religion of the Inca was replaced by Catholicism. The Inca aristocracy and artisans were incorporated into the colonial class system, while the peasants were reduced to servitude. In less developed areas, the Inca people maintained some of their cultural traditions and maintained economic transactions with modern industrial centers. Other South American Indians, such as the Araucanians, successfully resisted Spanish rule until they were repressed, assimilated or moved to reservations in the late 19th century.