If we assume, therefore, along with Rouget, that the Bushmen and Pygmy vocal practices stem from "a common root," then it's not difficult to see how the hocketed instrumental tradition could have originated from that same ancestral culture, some time between 72,000 and over 100,000 years ago (according to the genetic estimates) and spread along with the spread of that culture to certain places in Africa where, in various forms, it survives today. This is somewhat different from the view expressed by Blench, who sees no structural relationship between P/B style and the one-or-two-note-per-instrument hocketing of the wind ensembles -- an opinion reinforced by Simha Arom, who, as I mentioned earlier, has stated that he's never heard any hocketing among any of the Pygmy groups he's studied.
As I see it, Blench's denial of that crucial connection may stem from a failure on his part to distinguish between three different types of P/B vocalizing, as presented in my Phylogenetic Map: A1, "Shouted Hocket," A2, "Interlocked Hocket," and A3, "Contrapuntal Interlock." The latter, characterized by relatively long, fluid lines, interweaving "contrapuntally" does, indeed, sound rather different from the more choppy one or two note interchanges of the wind groups. But the other styles, A1 and A2, often simpler, possibly less interesting musically, and thus perhaps overlooked by Blench (and also Arom), do most definitely employ a very straightforward and clear form of hocket, in a manner quite similar to what is found in the wind ensembles.
The details of such performances are often obscured in recordings, since Pygmy and Bushmen polyphony is notoriously difficult to sort out by ear. Fortunately, I've been able to find a very clearly notated transcription in an excellent book by Michelle Kisliuk, an ethnomusicologist who spent enough time among the Aka to learn their songs (and dances) well enough to participate. (See Kisliuk, Seize the Dance, Oxford Univ. Press, 1998, p. 42.)
Kisliuk's notation, based not simply on listening and/or analysis, but her intimate knowledge of what happens in every detail of this music, represents a kind of "summary" of certain basic elements as they might be juxtaposed in a given performance. Her intent is to give the reader a general sense of what can happen at any point in the three "measure" song, as it is continually repeated and varied, and is thus more effective in reflecting the basic structure than a more literal transcription would be.
It's hard to understand, given such a transcription, how someone so well acquainted with Aka music as Arom could deny any knowledge of hocket in their music. The very striking similarities with the wind ensemble traditions he's documented are immediately apparent from the layout of the lowest three parts, each of which is limited to two notes which do indeed interlock with one another in classic hocket style. There are other examples of very similar sorts of vocal hocket in Kisliuk's book as well, e.g. on pp. 93, 137 and 138. She explicitly refers to this practice by name on p. 136. And, of course, many other very experienced musicologists have noted the importance of the hocket principle in Pygmy and Bushmen music. While, indeed, certain details are often obscured in recordings, and many performances do feature sustained melodic passages with fewer gaps, as in what I've called style A3, there is no question in my mind that a very deep structural affinity between P/B style and instrumental hocket exists.