<P> Several species of turtles, and the slender - snouted, Nile and dwarf crocodile are native to the Congo River Basin . African manatees inhabit the lower parts of the river . </P> <P> The entire Congo basin is populated by Bantu peoples, divided into several hundred ethnic or tribal groups (see ethnic groups of the Democratic Republic of the Congo). Bantu expansion is estimated to have reached the Middle Congo by about 500 BC, and the Upper Congo by the first century AD . Remnants of the aboriginal population displaced by the Bantu migration, Pygmies / Abatwa of the Ubangian phylum, remain in the remote forest areas of the Congo basin . </P> <P> The Kingdom of Kongo was formed around 1400 on the left banks of the lower Congo River . Its territorial control along the river remained limited to what corresponds to the modern Bas - Congo province . European exploration of the Congo begins in 1482, when Portuguese explorer Diogo Cão discovered the river estuary (likely in August 1482), which he marked by a Padrão, or stone pillar (still existing, but only in fragments) erected on Shark Point . Cão also sailed up the river for a short distance, establishing contact with the Kingdom of Congo . The full course of the river remained unknown throughout the early modern period . </P> <P> The upper Congo basin runs west of the Albertine Rift . Its connection to the Congo was unknown until 1877 . The extreme northeast of the Congo basin was reached by the Nilotic expansion at some point between the 15th and 18th centuries, by the ancestors of the Southern Luo speaking Alur people . Francisco de Lacerda following the Zambezi reached the uppermost part of the Congo basin (the Kazembe in the upper Luapula basin) in 1796 . </P>

Why is river congo known as the highway