Overview
Haplogroup B1-M236 is a rare and deeply rooted branch of haplogroup B that diverges early from B-M60. It represents an ancient paternal lineage that likely persisted in small forager groups in northern, western and northeastern Africa. Compared to the far more widespread B2-M182, B1-M236 shows limited branching depth and a highly fragmented geographic distribution. This pattern reflects a lineage that did not take part in Holocene expansions such as the Bantu migration or pastoralist dispersals along the eastern African corridor.
The rarity of B1-M236 in modern populations and its extremely deep age make it a valuable reference for studying ancient African structure. Unlike B2a or B2b, which correlate with major demographic events, B1-M236 preserves a signature of pre-Holocene population patterns that were later diminished due to expansions of E-M2, J, R1b-V88 and other dominant lineages.
Geographic distribution
B1-M236 is most frequent at low levels in parts of West Africa, including among Fulani-associated pastoralist groups, northern Nigerian and Chadian populations, and individuals from Mali and Mauritania. It is also detected sporadically in Northeast Africa, particularly Sudan and Eritrea, where it forms a minor ancient substratum.
In North Africa, B1-M236 occasionally appears in Moroccan, Libyan and Egyptian contexts, usually at low frequencies and often in communities with demonstrable ancient Saharan roots. Outside Africa, rare B1 lineages have been reported in the Arabian Peninsula, particularly in Yemen and western Saudi Arabia, likely introduced via trans-Red Sea movements and pre-Islamic trade routes. These distributions reinforce the interpretation of B1 as an ancient but non-expansive lineage.
Ancient DNA
- No ancient individual has yet been definitively assigned to B1-M236, but its geographic distribution is consistent with Pleistocene forager populations of the Sahara-Sahel region prior to major Holocene expansions.
- Population modeling based on present-day B1 diversity suggests that the lineage may have originated in regions adjacent to the ancient Green Sahara corridor, where fluctuating climatic cycles supported episodic forager mobility.
- Low-density occurrences of B1 in Northeast Africa agree with archaeological evidence for repeated contacts between Nile Valley groups and Saharan foragers during humid phases of the Pleistocene and early Holocene.
Phylogeny & subclades
B1-M236 shows limited internal branching compared to B2-M182. Its shallow phylogeny consists mostly of B1* basal lineages and a small number of derived branches that remain poorly sampled. Some phylogenetic studies suggest minor internal divisions within B1 that likely correspond to early regional isolates in West Africa and the central Sahara, but these clades have not yet received stable marker-based names. The lineage’s low diversity reflects long-term small population sizes and partial discontinuities caused by later demographic expansions.
- B1* (basal B1 lineages)
- Minor micro-branches found in West Africa and the Sahel
- Potential unclassified B1-derived clusters identified in recent whole Y sequencing
Notes & context
Although B1-M236 is rare, it plays an important role in clarifying the structure of early haplogroup B. Its distribution highlights regions where ancient forager populations persisted into the Holocene despite the later dominance of haplogroup E and other expanding lineages. Because B1 does not correlate with later large-scale demographic events, its presence can help identify remnants of ancient paternal diversity in regions like the Sahel, the central Sahara and parts of Northeast Africa.
References & external links