Evidence from digs at Shum Laka in the Northwest Region shows human occupation in Cameroon dating back 30,000 years.[15][16] The longest continuous inhabitants are groups such as the Baka (Pygmies).[17] From there, Bantu migrations into eastern, southern and central Africa are believed to have occurred about 2,000 years ago.[18] The Sao culture arose around Lake Chad, c. 500 CE, and gave way to the Kanem and its successor state, the Bornu Empire. Kingdoms, fondoms, and chiefdoms arose in the west.[19] Portuguese sailors reached the coast in 1472. They noted an abundance of the ghost shrimp Lepidophthalmus turneranus in the Wouri River and named it Rio dos Camarões (Shrimp River), which became Cameroon in English.[20] Over the following few centuries, European interests regularised trade with the coastal peoples, and Christian missionaries pushed inland.[21] In 1896, Sultan Ibrahim Njoya created the Bamum script, or Shu Mom, for the Bamum language.[22][23] It is taught in Cameroon today by the Bamum Scripts and Archives Project.[23] German rule[edit] Main article: Kamerun Germany began to establish roots in Cameroon in 1868 when the Woermann Company of Hamburg built a warehouse. It was built on the estuary of the Wouri River. Later, Gustav Nachtigal made a treaty with one of the local kings to annex the region for the German emperor.[24] The German Empire claimed the territory as the colony of Kamerun in 1884 and began a steady push inland; the natives resisted. Under the aegis of Germany, commercial companies were local administrations. These concessions used forced labour to run profitable banana, rubber, palm oil, and cocoa plantations.[24] Even infrastructure projects relied on a regimen of forced labour. This economic policy was much criticised by the other colonial powers.[25] French and British rule[edit] Main articles: French Cameroon and British Cameroon Leaders of the pro-independence UPC With the defeat of Germany in World War I, Kamerun became a League of Nations mandate territory and was split into French Cameroon (French: Cameroun) and British Cameroon in 1919. France integrated the economy of Cameroon with that of France[26] and improved the infrastructure with capital investments and skilled workers, modifying the colonial system of forced labour.[25] Britain offered German owned plantations to the highest bidder with the intent of paying the proceeds into a World War I reparations account. But few investors were willing to buy at the London auctions. Eventually Britain sold the majority of German plantations in British Cameroon back to their original German owners and opened up African maritime ports for German trade. The British also encouraged German investment in the Tanganyika Territory. German companies built warehouses in Douala but were not allowed to purchase land.[27] The British administered their territory from neighbouring Nigeria. Natives complained that this made them a neglected "colony of a colony". Nigerian migrant workers flocked to Southern Cameroons, ending forced labour altogether but angering the local natives, who felt swamped.[28] The League of Nations mandates were converted into United Nations Trusteeships in 1946, and the question of independence became a pressing issue in French Cameroon.[26] France outlawed the pro-independence political party, the Union of the Peoples of Cameroon (French: Union des Populations du Cameroun, UPC), on 13 July 1955.[29] This prompted a long guerrilla war waged by the UPC and the assassination of several of the party's leaders, including Ruben Um Nyobè, Félix-Roland Moumié and Ernest Ouandie. In the British Cameroons, the question was whether to reunify with French Cameroon or join Nigeria; the British ruled out the option of independence.[30] Independence[edit] On 1 January 1960, French Cameroun gained independence from France under President Ahmadou Ahidjo as the Republic of Cameroon. Federal Republic of Cameroon[edit] Flag of the Federal Republic of Cameroon On 1 October 1961, the formerly British Southern Cameroons gained independence from the United Kingdom by vote of the UN General Assembly and merged into the Republic of Cameroon to form the Federal Republic of Cameroon. The federal republic was composed of two federated states, East Cameroon and West Cameroon, each with its own legislature, government, and prime minister. 1 October is now observed as Unification Day, a public holiday.[31] Ahidjo used the ongoing war with the UPC to concentrate power in the presidency, continuing with this even after the suppression of the UPC in 1971.[32] United Republic of Cameroon and Republic of Cameroon[edit] Former president Ahmadou Ahidjo ruled from 1960 until 1982. Ahidjo's political party, the Cameroon National Union (CNU), became the sole legal political party on 1 September 1966, and on 20 May 1972, a referendum was passed to abolish the federal system of government in favour of a United Republic of Cameroon, headed from Yaoundé.[33] This day is now the country's National Day, a public holiday.[34] Ahidjo pursued an economic policy of planned liberalism, prioritising cash crops and petroleum development. The government used oil money to create a national cash reserve, pay farmers, and finance major development projects; however, many initiatives failed when Ahidjo appointed unqualified allies to direct them.[35] The national flag was changed on 20 May 1975 with the two stars removed and replaced with a large central star as a symbol of national unity. Ahidjo stepped down on 4 November 1982 and left power to his constitutional successor, Paul Biya. However, Ahidjo remained in control of the CNU and tried to run the country from behind the scenes until Biya and his allies pressured him into resigning. Biya began his administration by moving toward a more democratic government, but a failed coup d'état nudged him toward the leadership style of his predecessor.[36] In 1987, Dja Faunal Reserve, Cameroon's first World Heritage Site, was inscribed on the list by UNESCO.[37] An economic crisis took effect in the mid-1980s to late 1990s as a result of international economic conditions, drought, falling petroleum prices, and years of corruption, mismanagement, and cronyism. Cameroon turned to foreign aid, cut government spending, and privatised industries. With the reintroduction of multi-party politics in December 1990, the former British Southern Cameroons pressure groups called for greater autonomy, and the Southern Cameroons National Council advocated complete secession as the Republic of Ambazonia.[38] The 1992 Labour Code of Cameroon gives workers the freedom to belong to a trade union or not to belong to any trade union at all. It is the choice of a worker to join any trade union in their occupation since there is more than one trade union in each occupation.[39]