Pygmy & Bantu ethnogenesis in Central Africa

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 Central African population no more than ~70,000 YBP. After a period of isolation, accounting for current phenotypic differences between AGR and PHG, gene flow between the ancestors of the two groups began to occur no more than ~40,000 YBP. Our data are consistent with continuous maternal gene flow from PHG-to-(proto)AGR over a long period. Unlike that of PHG, the proto-AGR maternal gene pool was enriched by the more recent arrival of L0a, L2, and L3 carriers, coinciding with the introduction of Late Stone Age technologies in the region and paving the way for the most important demographic, linguistic, and technological event in subSaharan Africa: the Bantu expansions.

I actually think that this is a good analogy with the Slavic case in some ways. The Bantu Expansion to the east and south seems to resemble the Slavic expansion (which doesn't have a specific name) to the north and east. In both cases you have pre-literate groups of farmers who seem to be pushing into new territory in an ad hoc manner, and absorb local group which only remain extant as residua. And like the Slavic language, the Bantu languages are also broadly intelligible, suggesting a recent origin and rapid radiation. That being said, the relationship of the Finnic peoples is strongly supported by linguistics and to a lesser extent by genetics. The Pygmies can be though plausibly argued to be distinct instances of adaptation of disparate peoples to life in the deep forest (note the well known genetic differences between eastern and western Pygmy groups and their tendency to speak the language of the surrounding agricultural populations), so the analogy is not perfect. But that's why you do the research.

Update: Greg Laden, who has lived amongst the Pygmies, comments:

Eastern Pygmies live along side non-Bantu (Sudanic) people. Western-central pygmies do.

In all cases, pygmy women marry into villager households, and their children are then always considered as villagers (bantu or sudanic) thereafter. There is no other gene flow between the populations that is known.

Western central pygmies and their non-pygmy neibhors often overlap to a considerable degree physically, and the best way to tell them apart, I am told by my colleagues who work there, is by their dress and other cultural fixtures. Eastern Pygmies and their Sudanic neighbors look as different as any two groups of people I've ever observed.

I believe that the sudanic/pygmy contact in the eastern region is less than 1,000 years old, and the bantu/pygmy contact in the western region is several thousand years old.

So, you've gotta figure all this in.