sub-Saharan East Africa Research Articles

Genetic diversity on the Comoros Islands shows early seafaring as major determinant of human biocultural evolution in the Western Indian Ocean

The Comoros Islands are situated off the coast of East Africa, at the northern entrance of the channel of Mozambique. Contemporary Comoros society displays linguistic, cultural and religious features that are indicators of interactions between African, Middle Eastern and Southeast Asian (SEA) populations. Influences came from the north, brought by the Arab and Persian traders whose maritime routes extended to Madagascar by 700-900 AD. Influences also came from the Far East, with the long-distance colonisation by Austronesian seafarers that reached Madagascar 1500 years ago. Indeed, strong genetic evidence for a SEA, but not a Middle Eastern, contribution has been found on Madagascar, but no genetic trace of either migration has been shown to exist in mainland Africa. Studying genetic diversity on the Comoros Islands could therefore provide new insights into human movement in the Indian Ocean. Here, we describe Y chromosomal and mitochondrial genetic variation in 577 Comorian islanders. We have defined 28 Y chromosomal and 9 mitochondrial lineages. We show the Comoros population to be a genetic mosaic, the result of tripartite gene flow from Africa, the Middle East and Southeast Asia. A distinctive profile of African haplogroups, shared with Madagascar, may be characteristic of coastal sub-Saharan East Africa. Finally, the absence of any maternal contribution from Western Eurasia strongly implicates male-dominated trade and religion as the drivers of gene flow from the North. The Comoros provides a first view of the genetic makeup of coastal East Africa.

Darwinian biophysics: Electrostatics and evolution in the kinetics of molecular binding

At the molecular level of biology, the competition for favorable outcomes has been shaped by evolution, just as in more familiar examples from ecological biology. At both levels, this competition is often based on raw speed. There are differences, of course. Most notably, a race between molecules is more often determined by diffusional dynamics than by inertial dynamics. The driving forces on molecules typically comprise electrostatic nudges rather than thundering hooves digging into soil. Electrostatic interactions can be surprisingly effective, however. The rate of degradation of the neurotransmitter acetylcholine by the synaptic enzyme acetylcholinesterase is known to be increased by a factor of up to a few hundred as a result of “electrostatic steering” of the positively charged acetylcholine molecule toward the predominantly negative active-site region of the enzyme (1). This tends to optimize the clearing and resetting of neuromuscular junctions and other cholinergic synapses, which offered a clear competitive advantage to our successful ancestors, relative to more sluggish individuals of their species who faced the same predators. Such selective pressures are also recorded in proteins at the next level of a hierarchy, in some of the venom molecules of snakes such as the green mamba that prey on small mammals in sub-Saharan East Africa. The green mamba toxin fasciculin-2 is a small protein whose positively charged surface is attracted to, and clamps down on, the active-site entrance of acetylcholinesterase, causing muscular activity of the unfortunate rat or other prey to cease. Here, again, the binding involves electrostatically steered diffusion, and the binding speed is increased by a factor of up to a few hundred by the electrostatic attraction between the proteins (1). Many other examples of electrostatically steered, diffusion-controlled processes are now known, including such familiar ones as the polymerization of actin (2, 3). In a recent issue of PNAS, a new article by Qin and Zhou greatly deepens our insight into these important processes, and extends the range of analysis to include reactions in which the rates may be influenced by events following the initial diffusional encounter (4).

The Myth of the Sultans in the Western Indian Ocean during the Nineteenth Century: A New Hypothesis

AbstractThe power of the Al Bu Sa'id Sultans of Oman was widely known as based on delicate balances of forces (and ethnic-social groups), deeply different among them. In fact, the elements that composed the nineteenth century Omani leadership were, and had always been, generally 'divided' amongst three different ethnic groups: the Baluch, the Asian merchant communities and the African regional leaders (Mwiny Mkuu). Within this framework, the role played by European Powers, particularly by the Treaties signed between the Sultans of Oman and the East India Company for abolishing slavery, and by the arms trade was crucial for the development of the Gulf and the Western Indian Ocean international networks They highly contributed to the gradual 'shifting' of the Omanis from the slave trade to clove and spice cultivation – the major economic source of Zanzibar Island – along the coastal area of Sub-Saharan East Africa. The role played by the Omani Sultans – the myth – within the western traditional historiography, which often described them as firmly controlling both the Arabian and African littorals and the major trading ports of the Western Indian Ocean during the nineteenth century, will be reexamined in this paper, taking into account recent research studies and international debates in the topic. The new hypothesis consists of a different perception of the concepts of power and control (political and territorial) of the Western Indian Ocean littorals by the most famous of the Sultans of Oman during the nineteenth century: Saiyid Sa'id bin Sultan Al Bu Sa'id.

Genetic encapsulation among Near Eastern populations

This report aims to genetically characterize the relationships between geographically targeted human populations covering an expanse from east sub-Saharan Africa northeastward into northern India with an emphasis on the Near East. A number of parameters of population genetics interest were examined based on allele frequencies from 15 forensic autosomal STR markers [D8S1179, D21S11, D7S820, CSF1PO, D3S1358, TH01, D13S317, D16S539, D2S1338, D19S433, vWA, TPOX, D18S51, D5S818, and FGA]. The phylogenetic analyses generated from genetic profiles of 885 individuals indicate that populations west of and including Iran have experienced substantial gene flow. Accordingly, our findings delineate a region of genetic homogeneity concentrated within the Near East with increasing genetic differentiation moving south into Africa and further east into Asia. We suggest that the Saharan desert, the Hindu Kush mountain range and perhaps to a lesser extent, the deserts of Iran may have acted as southern, eastern and northern geographical barriers, respectively, forming a genetic enclosure that allows limited gene flow outside the Near East. The biparental genetic landscape supports a picture of close contact between the Arab and Persian populations, perhaps beginning during the initial settlement of Asia from Africa extending to recent times.

Imported Tickborne Relapsing Fever, France

Imported Tickborne Relapsing Fever, France

High-resolution record of cyclic climatic change during the past 4 ka from Lake Turkana, Kenya

Profiles of carbonate content and lamination thickness in an 11.3 m core from Lake Turkana are interpreted as a record of climatic change for the past 4 ka. On a time scale of millennia, the data agree with other paleohydrologic records from sub-Saharan east Africa. Time-series analysis of both data sets reveal periods of about 270,200, 165, and 100 yr. The thickness data suggest additional periods of about 78, 44, 31, 25, and possibly 20 yr. The sediments consist of laminated light and dark couplets, which are interpreted as a response to an average 4-yr variability in the hydrology of the Ethiopian Pla- teau. We suggest that this may be a feedback from the El Nino-Southern Oscillation.