The Oromo (pron. ˈɒrəmoʊ Oromo: Oromoo) are a Cushitic ethnic group native to the Oromia region of Ethiopia and parts of Northern Kenya, who speak the Oromo language (also called Afaan Oromoo), which is part of the Cushitic branch of the Afroasiatic language family. They are one of the largest ethnic groups in Ethiopia. According to the last Ethiopian census of 2007 the Oromo numbered 25,488,344 people or 34.5% of the Ethiopian population. The Oromo people traditionally used the gadaa system as the primary form of governance. A leader is elected by the gadaa system and their term lasts eight years, with an election taking place at the end of those eight years. Although most modern Oromos are Muslims and Christians, about 3% practice Waaqeffanna, the native ancient monotheistic religion of Oromos. The Oromo people are one of the oldest cushitic peoples inhabiting the Horn of Africa, as there is still no correct estimate of the history of their settlement in the region, but many indications suggest that they have been living in north Kenya and south-east Ethiopia for more than 7000 years specifically between Lake Chamo and Bale Mountains. Subsequent colonial era documents mention and refer to the Oromo people as Galla, which has now developed derogatory connotations, but these documents were generally written by members of other ethnic groups. The first verifiable record mentioning the Oromo people by a European cartographer is in the map made by the Italian Fra Mauro in 1460, which uses the term Galla. According to Herbert S. Lewis, both the Oromo and the Somali people originated in southern Ethiopia but the Somali expanded to the east and north much earlier than the Galla, and the Galla lived only in southern Ethiopia and northern Kenya until the Oromo migrations began about 1530. The term Galla, stated Juxon Barton in 1924, was in use for Oromo people by Abyssinians and Arabs. It was a term for a river and a forest, as well as for the pastoral people established in the highlands of southern Ethiopia.