Peruvians are the citizens of Peru. What is now Peru has been inhabited for several millennia by cultures such as the Caral before the Spanish conquest in the 16th century. Peruvian population decreased from an estimated 5–9 million in the 1520s to around 600,000 in 1620 mainly because of infectious diseases carried by the Spanish. Spaniards and Africans arrived in large numbers in 1532 under colonial rule, mixing widely with each other and with Native Peruvians. During the Republic, there has been a gradual immigration of European people. Chinese and Japanese arrived in large numbers at the end of the 19th century.