There's a new paper out in Nature which details the genomes of several Bushmen, and how they relate to other humans, and one particular Bantu speaking individual, archbishop Desmond Tutu. It's open access, Complete Khoisan and Bantu genomes from southern Africa. I haven't read the whole thing, but it is probably best to check out Ed Yong's very thorough review first. Here's an interesting point Ed brings up:
Most surprising of all, many of their unique SNPs are actually fairly recent developments. The Bushmen are one of the oldest human groups on the planet and you might expect their genes to reflect humanity's most ancestral state. But not the SNPs - Schuster found that only 6% of !Gubi's newfound SNPs matched the equivalent sequences in the chimpanzee genome; by comparison, the same positions in the human reference genome are an 87% match for the chimp one. They can't be ancestral sequences. They must have turned up after the Bushmen dynasty diverged from other human populations, and they provide hints about the history of this most ancient of human lineages.
The paper itself uses the phrase "the oldest known lineage of modern human." It's pretty ubiquitous as a description for the Bushmen and related peoples. But as you probably know, I don't think it's that helpful, though the usage of the term "lineage" makes the topology of the phylogenetic tree clear at least. Perhaps more evidence of derived alleles in "ancient populations" will shift the definitional ground a bit.... Citation: Schuster et al., Complete Khoisan and Bantu genomes from southern Africa, doi:10.1038/nature08795