Monday, January 16, 2012

Genetic and linguistic perspectives on Afroasiatic

Via GNXP, I hear there's been a new study on North African genetics: Genomic Ancestry of North Africans Supports Back-to-Africa Migrations. It provides an interesting cross-check on linguistic hypotheses.

In brief, the story these geneticists propose is: the main ancestors of modern North Africans, in particular Berbers, migrated into North Africa at least 12,000 and perhaps as much as 40,000 years ago; this "Maghrebi" component is close to Western Eurasian populations, and is dominant in most of their Moroccan and Algerian samples (and prominent in Libya). Arabs migrated in more recently starting 1,400 years ago, and Near Eastern influence is prominent throughout, especially in Libya, and dominant in Egypt. The Sub-Saharan African component seems to have arrived even later (~1,200 years ago in southern Morocco) and thus probably reflects the trans-Saharan slave trade; in Morocco it looks West African, while in Egypt it appears more diverse. Some European admixture is visible in Algeria and northern Morocco as well, but its nature is not clear. The data set is a bit small: a better coverage of Sahelian populations would be highly desirable, as would more Near Eastern populations, and one wonders where the ancient Egyptians fit in. However, the overall picture seems reasonable.

The more recent stages fit trivially with the detailed linguistic and historical data available (see my earlier post on linguistic traces of sub-Saharan immigration into North Africa), but the genetic divergence between Maghrebis and western Eurasian populations takes us into a realm where both fields offer much less certainty. Linguistically, we know that Berber, Semitic, and Egyptian are all distantly related to one another (and to Chadic and Cushitic, though that doesn't show up in the genetic data here); but we don't know when they split apart. There is no generally agreed upon method for dating linguistic divergences, and Swadesh's original "radioactive decay" glottochronological formula has proved too poor an approximation to be relied upon. However, a much-modified glottochronological formula was more recently proposed by Sergei Starostin in an attempt to fit a curve of attested data points. As it happens, two of his followers, George Starostin and Alexander Militarev, have ventured to offer estimates for Afroasiatic; for the split between Semitic and Berber, they respectively estimate 9,700 or 11,000 years ago. This seems strikingly close to the lower limit of the geneticists' estimate here. But even if this estimate is rejected, if the divergence date is anywhere near what the genetics is suggesting, then we have to conclude that genetic relationships older than 10,000 years can be discerned, contrary to some claims in the literature.

There is a way around this: one could propose a pre-Phoenician immigration that changed the language but had relatively little impact on the gene pool. In fact, such an event may have to be postulated for Afroasiatic's history in at least some areas anyway: speakers of one Chadic language are represented in this paper - Hausa - and their genes look nothing like North Africans or Near Easterners. However, it hardly seems like a parsimonious hypothesis in this case, given the split dates suggested. So... is this a corroboration of Starostin's method, or just a lucky guess?


John Cowan said...

What has always seemed strange to me in AA is the status of Egyptian. It's geographically central, adjoining Semitic, Berber, and Cushitic; it was the first to be written and the first to be the bearer of a high civilization. And yet while it is distinctively AA, it is an isolate within AA, the usual fate of marginal and peripheral languages.

One might argue that all of its immediate relatives were lost without trace, replaced by (Standard) Egyptian, I suppose. But why is it so different from the other AA families? The only thing I discover from Wikipedia is that nobody agrees even on what its nearest relatives are: all of Semitic, Chado-Semitic, Semito-Berber, and Chado-Berber have been proposed as sister groups.

Michael Grant said...

I have nothing to add to this (other than surprise at the expectation that anything could be told of languages that split that far back), but I just wanted to say I found this very interesting to read.

Malam said...

Berber languages are related to chadic ,so does Berber peoples to chadic peoples.
The R-V88 found among chadic people was also found in high velocity among Siwa Berber of western Egypt.

Michael Hahn said...

I could imagine that the Hausa speakers might perhaps be not so indicative, as it is a widely used lingua franca and probably absorbed speakers of other, non-AA languages. Maybe the genes of speakers of smaller Chadic languages would be more interesting.

@John: I agree, that's somewhat puzzling. But I think all the differences (at least in morphology) can be attributed to loss. The only area where Egyptian is definitely different (we don't know about the a-plural and case) is verbal conjugation, while it shares with Semitic (and Berber) a lot of features that Chadic and Omotic lack, e.g., the PAA suffix conjugation, absolute pronouns, the dual in -y, the genitive/nisba ending -i/y, .... So I think it's quite plausible that Egyptian radically changed its verbal system, but preserved many innovations which Chadic and Omotic maybe never had.

Michael Hahn said...

@John: I forgot to mention: There has been some speculation that an Egyptian-speaking tribe lived in the Western Desert in the 3rd millenium B.C., cf.

Gerhard Fecht, Die Ḥ3.tjw-ˁ von Ṯḥnw, eine ägyptische Völkerschaft in der Westwüste, in: Zeitschrift der Deutschen Morgenländischen Gesellschaft Band 106, Heft 1 1956 (=Neue Folge Band 31) Steiner, Wiesbaden 1956. p. 37-60

By the end of the 2nd millenium B.C., the Western Desert was definitely populated by Berber-speaking tribes, as shown by Berber names and titles in the Egyptian sources. So I would assume that the Egyptian branch was originally spoken in the Nile valley and the adjacent desert regions until they were replaced by the migration of Berber tribes. This would presumably also be compatible with some archaeologically motivated ideas about early migrations of Egyptians and Berbers.

Lameen Souag الأمين سواق said...

John: Egyptian probably absorbed all its nearest relatives in the course of becoming the only Afroasiatic language of the Nile Valley; Semitic and Berber had probably already split off by the early dynastic period.

Malam: True for Siwa, but the Siwis genetically look completely different from other Berber groups. To figure out the whole story we'll need Libyan data, and not much of that has come out yet.

Michael: It's not quite that simple; the linguistic (as opposed to ethnographic) evidence for Berber presence at this period seems to be much weaker than commonly thought, as noted in an earlier post.