Originally settled by Pygmy peoples, they were largely replaced and absorbed by Bantu tribes as they migrated. By the 18th century, a Myeni-speaking kingdom known as the Kingdom of Orungu formed in Gabon.  It was able to become a powerful trading center mainly due to its ability to purchase and sell slaves. The kingdom fell with the demise of the slave trade in the 1870s. Since its independence from France in 1960, the sovereign state of Gabon has had three presidents. In the early 1990s, Gabon introduced a multi-party system and a new democratic constitution that allowed for a more transparent electoral process and reformed many governmental institutions.