An introduction to the sub saharan africa and its demography

Agricultural Statistics The history of agricultural statistics in South Africa goes back as far back as the beginning of the 20th century. With the exception of the World Wars and great depression years, an agricultural census was conducted on annual basis in the first half of the 20th century.

An introduction to the sub saharan africa and its demography

Summary Statistics of Populations Samples. Extended haplotypes of a subset of our Sub-Saharan samples from HGDP project that were used in our study Table S1 and for which genome-wide genotypes were available at http: The correspondence between the extended haplotypes below and the Fig.

An introduction to the sub saharan africa and its demography

The analyses revealed a complex genetic structure of the Africans that contributed to the emergence of modern humans. Age estimates of these lineages, older than coalescence times of uniparentally inherited markers, raise the question whether contemporary humans originated from a single population or as an amalgamation of different populations separated by years of independent evolution, thus suggesting a greater antiquity of our species than generally assumed.

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An East African population that gave rise to non-Africans underwent a selective sweep affecting the subcentromeric region where MTMR8 is located.

This and similar sweeps in four other regions of the X chromosome, documented in the literature, effectively reduced genetic diversity of non-African chromosomes and therefore may have exacerbated the effect of the demographic bottleneck usually ascribed to the out of Africa migration.

Our data is suggestive, however, that a bottleneck, occurred in Africa before range expansion. Introduction In light of recent data, human evolutionary history looks much more complex than what geneticists postulated only a decade ago [1].

For example, in addition to new evidence of archaic admixture outside Africa [2] — [4]the time scale of human evolution needs to be extended. The generation span of humans and their ancestors appears longer than was previously estimated, and an older age of independent human lineages that collectively contributed to the modern genome was documented [5] — [10].

Nevertheless, the greatest genetic diversity among human populations is observed in sub-Saharan Africa, which leads to revisiting the old question [11][12]: Is greater genetic diversity in Africa due only to older and larger ancestral African population sizes as compared to those outside of Africa, or does it reflect the impact primarily of the out of Africa population bottleneck s in reducing the genetic diversity outside Africa?

If at the time of out-of-Africa migration Africans and migrant populations did not differ in their genetic structure, but African populations stayed larger than non-Africans, greater African diversity would be expected to result from an accumulation of new low frequency local variants.

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In contrast, a restricted sampling of alleles due to a stringent out-of-Africa bottleneck [13] would cause a relative paucity of the genetic diversity in non-Africans [14].

Both above scenarios turned out to be too simplistic. New findings have provided support for the idea that genetic diversity of non-Africans was additionally enriched by admixture with Neandertals [2][4] and Denisovans [3]. In Africa, low frequency derived alleles in the dys44 segment are spread on different haplotypes, which implies substantial number of recombinations and gene conversions, and thus long evolutionary time since the corresponding mutations have occurred [10].

Such alleles are necessarily ancient and their limited occurrence suggested archaic admixture within Africa itself, supported by additional evidence [9][15] — [18].

Although extensive gene flow shaped the diversity of sub-Saharan Africans over various periods [19] — [22]traces of the ancestral subdivisions can still be recognized in the genetic record [6][20][23] — [26] ; the homogenizing effect of gene flow that in general will partially conceal the record of the ancestral population structure, is expected to be less obvious in areas of low recombination and strong linkage disequilibrium [27].

Studying loci with such characteristics is therefore of great significance in terms of unravelling human population histories. In depth analyses of single autosomal and X-linked loci complement studies of uniparentally inherited mitogenomes and Y-chromosomes with their well resolved genealogies.

However, the time depth of autosomal or X-linked genealogies is roughly four and three-times deeper, respectively, than that of the genealogies of the uniparentally inherited loci.

Here we studied an 11 kb DNA segment with low-recombination frequencies [30] located in the Xq This segment is located within the myotubularin related protein 8 gene MTMR8in the centromeric portion of the X chromosome, earlier found to have reduced sequence diversity in non-African populations [31] — [33].

Our study showed that MTMR8 diversity in sub-Saharan Africans can reveal much about the evolutionary history of these populations. Our results are consistent with the enrichment of the African diversity through fragmentation of its populations over long periods of their history as well as by admixture among archaic populations.Given its characteristics we propose it as a plausible candidate to represent an archaic lineage within Sub-Saharan Africa, (see Discussion).

The other very old haplotypes HH21 and H17 are principally Khoe-San, from southern Africa, representing 61% of their chromosomes. Ethnopolitical demography and democracy in sub-Saharan Africa Ethnicity, like all sources of social cleavages, can be activated strategically by social actors, often to advance political goals.

Such diversity and complexity are the reality of Sub-Saharan Africa (SSA) today. The major focus of this book is on SSA from the Sahel south.

Approximately million children between birth and age 6 . DEMOCRACY IN AFRICA Vol. 1 No.

An introduction to the sub saharan africa and its demography

1 Fall A Publication of the Institute for Democracy in Africa St. Thomas University, Miami, Florida Editor: JaNice Parks. A shortage of health professionals compounded by migration of health workers from sub-Saharan Africa to other parts of the world (namely English-speaking nations such as the United States and the United Kingdom) has negatively impacted productivity and efficacy of the region’s health systems.

The Muqaddimah, also known as the Muqaddimah of Ibn Khaldun (Arabic: مقدّمة ابن خلدون ‎) or Ibn Khaldun's Prolegomena (Ancient Greek: Προλεγόμενα), is a book written by the Arab historian Ibn Khaldun in which records an early view of universal modern thinkers view it as the first work dealing with the social sciences of sociology, demography.

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