Hoisin hunter-gatherers are some of the earliest known modern human inhabitants of the area. They were largely replaced by Bantus during the Bantu migrations, though small numbers of Khoisans remain in parts of southern Angola. The culture is mainly native Bantu mixed with Portuguese aspects. Angola was a former Portuguese colony for 500 years, but until the 1920s, there was little investment and the Portuguese presence was confined to the coastal towns. There a creole or mestizo class evolved. The interior was exploited as a source of slaves. Even after the abolition of slavery, it was a source of contract labor. Angolans began to agitate for independence in the mid-1950s. Three nationalist groups were formed: the MPLA in 1956, the FNLA in 1958 and UNITA in 1966.