The peopling of Sub-Saharan Africa: The case study of Cameroon

Abstract

This study analyzes the distribution of ten protein genetic polymorphisms in eighteen populations from the most densely inhabited areas of Cameroon. The languages spoken belong to three different linguistic families [Afro-Asiatic (AA), Nilo-Saharan (NS) and Niger-Kordofanian (NK)]. The analysis of variation of allele frequencies indicates that the level of genetic interpopulation differentiation is rather low (F(st) = 0.011 +/- 0.006) but statistically significant (p < 0.001). This result is not unexpected because of the relatively small geographic area covered by our survey. This value is also significantly lower than the one estimated for other groups of African populations. Among the factors responsible for this, we discuss the possible role of gene flow. There is a considerable genetic differentiation among the AA populations of north Cameroon as is to be expected because they all originated from the first agriculturists of the farming "savanna complex." The Podowko and Uldeme are considerably different from all the other AA groups, probably due to the combined effect of genetic drift and isolation. In the case of the Wandala and Massa, our analyses suggest that genetic admixture with allogeneous groups (especially with the Kanuri) played an important role in determining their genetic differentiation from other AA speaking groups. The Bantu speaking populations (Bakaka, Bamileke Bassa and Ewondo, NK family, Benué Congo subfamily) settled in western and southern Cameroon are more tightly clustered than AA speaking groups. This result shows that the linguistic affinity among these four populations coincides with a substantial genetic similarity despite their different origin. Finally, the Fulbe are genetically distinct from all the populations that belong to their same linguistic phylum (NK), and closer to the neighboring Fali and Tupuri, eastern Adamawa speaking groups of north Cameroon.

Oculocutaneous albinism type 2 (OCA2) with homozygous 2.7-kb deletion of the P gene and sickle cell disease in a Cameroonian family. Identification of a common TAG haplotype in the mutated P gene

“…homozygous for the bS-globin gene. Cameroon is of considerable anthropological interest for two historical reasons (Spedini et al 1999). First, the peopling of Cameroon involved a process of sedentarisation into three nuclei that are ancient and well documented.…”

“…Population inhabitants in this area are quite homogenous according to their ethnic languages, cultural attitudes, and their use of French. They belong to the Benue-Congo subfamily 3c, also referred to as the Bantu group (Spedini et al 1999). On the other hand, this area encompasses numerous ethnic groups: Douala, Bakundu, Bassa, CentralBantus (Banen, Yambassa), Semi-Bantus (Bamileke, Bamoun), Beti-Pahouins (Boulou, Eton, Ewondo, Fang) and Maka, who are affected by two frequent monogenic diseases: OCA2 and sickle cell anemia.…”

“…The founder effect is illustrated in the Balengou kingdom where the eighth and ninth kings, at the beginning of the twentieth century had albinism. These kings were polygamists, with 80-100 wives and 200-300 children, who were obligate heterozygotes; on the other hand, in the Bamileke tribe, marriages tended to occur within the same clan or town (Puri et al 1997) with a high endogamic rate of around 95% (Spedini et al 1999). A hypothetical scenario would be that the founder effect was the cause of the initial high proportion of albinos in this small endogamous population, which was then spread by migrating groups to other geographic regions followed by the rapid increase in size of that population (Woolf 2005).…”

“…The high endogamic rate (97-99%) in the Bamileke, Bassa, and Ewondo ethnic groups favours genetic drift (Spedini et al 1999), but these values seem to us overestimated because, for example, of the 40 Ewondo albinos actually recorded, 10 are related to another ethnic group, giving an endogamic rate of 75% (unpublished results).…”

“…It is generally accepted that the Bantu languages originated in the Middle-Benue valley between Nigeria and Cameroon approximately 3,000-4,000 years ago and then spread to other regions of sub-Saharan Africa (Spedini et al 1999).The presence of the 2.7-kb deletion mutation in Negroids of central African origin (Cameroon, Gabon, Congo, Democratic republic of Congo, Central African Republic) and in the Bantu-speaking Negroids of southern Africa (Zambia, Zimbabwe, Southern-Africa) suggests that the mutation likely arose before the divergence of these groups, estimated to have occurred 2,000-3,000 years ago (Stevens et al 1995(Stevens et al , 1997. We were able to estimate the age of the mutation using intragenic markers located on either side of a recombination hot spot, thus allowing us to use recombination rates from a fine-scale genetic map (Myers et al 2005), the estimated frequencies of different haplotypes associated with the mutation, the prevalence of the 2.7 kb mutation and the present effective population size (Table 2).…”