The site of highly developed kingdoms in the Middle Ages, the area came under British influence during the 19th century and was made into a single colony in 1914. Independence came in 1960 and the state became a federal republic in 1963, remaining a member of the Commonwealth. Oil was discovered in the 1960s and 1970s, since when Nigeria has emerged as one of the world's major exporters. The country was suspended from the Commonwealth in 1995-9 following the execution of the writer and activist Ken Saro-Wiwa （b. 1941） in 1995.