The oldest-known skeleton of a West African was found in Nigeria at Iwo Eleru; it is of a negroid man and is dated to 9250 ± 150 BC.
A human burial described as "proto-Negroid" was found at the base of the succession at Iwo Eleru with a date of 11200 ± 200 BP.
A single human skeleton some 12,000 years old from the lowest level of Iwo Eleru has been described as already showing specifically negroid features....
Note that there have been other candidates for the oldest Negroid skull, but in East rather than West Africa, such as Nazlet Khater (33,000 B.P., Upper Egypt) and Jebel Sahaba or Wadi Halfa (Mesolithic Nubia). However, these are very contentious and in all likelihood not Negroid, given that East Africans were still non-Negroid until much more recently.