Tanzania is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and the Indian Ocean to the east; Mozambique and Malawi to the south; Zambia to the southwest; and Rwanda, Burundi, and the Democratic Republic of the Congo to the west. Mount Kilimanjaro, Africa's highest mountain, is in northeastern Tanzania. Many important hominid fossils have been found in Tanzania, such as 6-million-year-old Pliocene hominid fossils. The genus Australopithecus ranged all over Africa 4 to 2 million years ago; and the oldest remains of the genus Homo are found near Lake Olduvai. Following the rise of Homo erectus 1.8 million years ago, humanity spread all over the Old World, and later in the New World and Australia under the species Homo sapiens. H. sapiens also overtook Africa and absorbed the older archaic species and subspecies of humanity. One of the oldest known ethnic groups still existing, the Hadzabe, appears to have originated in Tanzania, and their oral history recalls ancestors who were tall and were the first to use fire, medicine, and lived in caves, much like Homo erectus or Homo heidelbergensis who lived in the same region before them.