A · A1 · A1b · A1b1 · BT · B-M60 · B-M182 · B-M150 · B-M109
B-M109 (YFull B2a1)
Haplogroup B-M109 corresponds to one of the core radiations under B-M150 and is associated with major Holocene demographic processes in West and Central Africa. It is especially common among populations inhabiting regions linked to early Sahelian subsistence transitions, including proto-agricultural and mixed forager-farmer systems. B-M109 likely originated in the West–Central African corridor and expanded alongside communities occupying riverine and savanna ecological zones.
B-M109 is frequent in Nigeria, Cameroon and the Central African Republic and also occurs in Chad and northern Gabon. Moderate frequencies appear among western Congolese and some Great Lakes populations due to interactions during the early and late Bantu expansions. The clade is less common in Eastern Africa but present at low levels among groups with combined Sahelian and Central African ancestry. Rare cases outside Africa mostly represent recent historical movements.
B-M109 forms several internal clusters associated with West African populations and transitioning Sahelian groups. While not as deeply stratified as B-M112, B-M109 shows regionally coherent subdivisions that correlate with Holocene population expansions. Ongoing whole Y sequencing studies continue to refine its internal topology.
B-M109 is a key marker for tracing West and Central African population dynamics during the Holocene. Its distribution highlights the role of riverine and savanna ecologies in facilitating early expansions that shaped genetic diversity before and during Bantu-associated movements.