November 26, 2016
July 27, 2012
In many ways the image of Africa in the minds of Westerners has become a trope. The “Dark Continent,” eternal, and primal. Like many tropes the realized existence of this Africa is only within the imagination. The real Africa is far different. For there is no real Africa, there Africas. This truth is on my mind this week as two papers of great importance in understanding African genetic history finally saw the light of day. First, Dr. Joseph Pickrell et al. posted their preprint, The genetic prehistory of southern Africa, to arXiv. Second, out of the Tishkoff lab came Evolutionary History and Adaptation from High-Coverage Whole-Genome Sequences of Diverse African Hunter-Gatherers. Let me step aside here and observe a secondary, but non-trivial, detail. The former is an open access preprint. The second is a complete paper published in a relatively high impact journal, Cell, for which the paper itself does not seem typical or appropriate. This is fair enough, most people do not read journals front to back in this day. But unlike Dr. Joseph Pickrell’s paper the paper in Cell is paywalled, and from what I ...
June 10, 2011
In the post yesterday I reported what was generally known about the Horn of Africa, that its populations seem to lie between those of Sub-Saharan African and Eurasia genetically. This is totally reasonable as a function of geography, but there are also suggestions that this is not simply a function of isolation by distance (i.e., populations at position 0.5 on the interval 0.0 to 1.0 would presumably exhibit equal affinities in both directions due to gene flow). For example, you observe the almost total lack of “Bantu” genetic influence on the Semitic and Cushitic populations of the Horn of Africa, and the lack of Eurasian influence in groups to the south and west of the Horn except to some extent the Masai.
Tacking horizontally in terms of discipline, over the past few generations there has been a veritable cottage industry making the case for the recent origin of many ethno-linguistic populations through a process of cultural self-creation. Clearly there are many cases of this, some of them studied in depth by anthropologists (e.g., the shift from Dinka to Nuer identity). But there has been an unfortunate tendency to over-generalize ...
April 8, 2011
I recall years ago reading Spencer Wells discuss how important it was to sample “indigenous people”* before they were swallowed up by the cresting panmixia. Of course panmixia has to be conditioned on the fact that the vast majority of Han Chinese are stilling reproducing with other Han Chinese, and so forth. But it seems plausible to argue that the great agricultural Diasporas are only today swallowing up the residual of marginalized groups outside of the farming frontier. These populations which expanded from agricultural hearths over the Holocene may only be a shadow of the genetic variation which was once extant after the last Ice Age, as the thinly populated landscape was fractionated into endogamous networks as a matter of necessity rather than preference.
First, let’s recall that over the long term “effective population size” is defined by the harmonic mean. Concretely, a population of 1 billion can be far more genetically homogeneous than a population of 1,000, if, those 1 billion only recently expanded from far smaller populations. Imagine a toy example of two populations, A & B. They both begin in generation 1 with a population size ...
March 31, 2011
Image Credit: Mark Dingemanse
I recall years ago someone on the blog of Jonathan Edelstein, a soc.history.what-if alum as well, mentioning offhand that archaeologists had “debunked” the idea of the Bantu demographic expansion. Because, unfortunately, much of archaeology consists of ideologically contingent fashion it was certainly plausible to me that archaeologists had “debunked” the expansion of the Bantu peoples. But how to explain the clear linguistic uniformity of the Bantu dialects, from Xhosa of South Africa, up through Angola and Kenya, to Cameroon? One extreme model could be a sort of rapid cultural diffusion, perhaps mediated by a trivial demographic impact. The spread of English exhibits this hybrid dynamic. In some areas (e.g., Australia) there was a substantial, even dominant, English demographic migration coincident with the rise of Anglo culture. In other areas, such as Jamaica, by and large the crystallization of an Anglophone culture arose atop a different demographic substrate, which synthesized with the Anglo institutions (e.g., English language and Protestant religion). The United States could arguably be held up as a in-between case, with an English founding core population, around which there was an ...
February 8, 2011
The Lost History of Christianity: The Thousand-Year Golden Age of the Church in the Middle East, Africa, and Asia–and How It Died
Link to review: The view from somewhere smart.
February 4, 2011
Link to review: In the lands of the living God
Link to review: In the lands of the living God