Hello Baka Omubo. To answer your question West Africa has likely been inhabited by humans by 111,000 BCE or possibly even earlier. DNA evidence from modern West Africans show that much older humans who split from a common ancestor between 700,000-1.2 Million years ago began to live in the region by this 111,000 BCE date. Developing into distinct populations often termed "Basal, Archaic or Paleo Africans". Curiosly this 111,000 BCE date for the first ancient West Africans developing into population isolates seems to also coincide with the same 1st wet phase era of some of the earliest Out of Africa migrations. Population movements that would not only leave the continent but also undoubtedly migrate outwards in every direction, into West Africa included. Modern humans as we known them would not begin populating the region until the final years of the Out of Africa migrations. Around 60,000-40,000 BCE when Central & Northeast Africans as well as West Asians began settling. These ancient Ethiopian, Nile Valley, Eurasian and Pygmy like people by 35,000 BCE would assimilate with the Basal West Africans in a similar manner that Eurasians did before with Neanderthals/Denisovans. A 2nd wet phase that allowed increased travel and interaction was the catalyst for this union that resulted in modern West Africans. For the next few tens of millenia they would remain semi-isolated with no noticable major population exchanges except with their Central African neighbors. Instead developing a localized and vast genetic diversity that is uniquely West Africa. This would last until between 12,000-8000 BCE when groups outside of West Africa who practiced semi-sedentism began to expand. The advantage of common language and larger populations that sedentary cultures resulted in produced a variety of immigrants for West Africa such as Proto-Nilo-Saharans from East Africa, Mediterraneans from North Africa and Proto-Afro-Asiatics from West Asia. Some of the first signs of artistic expression and trade are found in the southern Sahara of West Africa in this 12,000-8,000 BCE timing. As early as 10,000 BCE in the form of cave drawings, funerary practices and more advanced stone tools. While these archaelogical findings are confined to the Sahara and only the northernmost portion of West Africa DNA evidence shows that in the same time period these newcomers did indeed mingle with southernmost West Africans as far as the coasts. Possibly diffusing into the forests from the savanna through the sahel and any archaeological evidences near impossible to recover in such a deteriorating environment. Likely bringing their semi-sedentary advancements with them. Then during a 3rd wet phase between 7,500-3,500 BCE the Sahara once again became fertile for travel. West Africa was no longer isolated from the changes of the Agricultural Revolution. Farming began as early as 5,200 BCE in the Sahel and Sahara. Animal husbandry also became a major factor during this 3rd wet phase. But towards 3,500 BCE a return to harsh desert conditions isolated West Africa once again. Forcing impossibly diverse groups from the savannas of the Sahara into every direction. Many of which retreating into northernmost West Africa where they could continue their savanna ways. Migrants from the Levant, Egypt, Libya, Nubia escaping similar desertification in their own lands also arrived between 4,000-2,000 BCE through the Chad Basin and ancient Niger Bend tributaries. This forced compression of diverse groups in a now smaller West Africa likely lead to exchanging cultural practices and the formation of the first "civilizations". ie Tichitt 2,000-1,600 BCE, Air Copper Smelters 3,000-2,500 BCE, Gajiganna 2,000-1,800 BCE, Kintapo 2,500-2,200 BCE. These 4 are arguably the first known civilizations of West Africa. I hope that answers your question. Have a good one!