A few weeks ago, I posted some stuff about what genetics an tell us about the Slavic expansion into the lands of Finno-Ugric tribes. Obviously, I don't think this is a line of inquiry is specific to that situation; and used judiciously it can add a lot of value toward answering many questions. From PNAS, Maternal traces of deep common ancestry and asymmetric gene flow between Pygmy hunter-gatherers and Bantu-speaking farmers (Open Access). Here's the conclusion:
The mtDNA data presented here suggest that the ancestral population in CA [Central Africa] that eventually gave rise to modern-day AGR [Bantu Agricultural] and PHG [Pygmy Hunter-Gather] populations, consisted principally of L1c clades that have survived to give the diverse forms observed among AGR, and essentially a single lineage among western PHG. The maternal gene pool composition of modern western PHG suggests a small number of ancestors that started to diverge from an ancestral ...
