Afghanistan: conduits of human migrations identified using AmpFlSTR markers.

This study describes autosomal STR profiles of the populations of South and North Afghanistan. A total of 188 unrelated individuals residing north (n = 42) and south (n = 146) of the Hindu Kush Range within the territory of Afghanistan were examined against the background of 54 geographically targeted reference populations from Eurasia and North East Africa. The main objective of this study was to investigate longitudinal gene flow across the Hindu Kush Range and Eurasia. Genetic differentiation tests between North and South Afghanistan generated insignificant genetic differences for all loci. Multidimensional scaling (MDS) plots based on Fst distances and Neighbor-Joining (N-J) analysis indicated genetic affinities between the Afghani groups and Indian/Near East/West Asian populations. Admixture and Structure analyses demonstrate a gradient of genetic continuity within a major east to west cline that includes North and South Afghanistan as intermediate populations. Overall, although Afghanistan is surrounded by a number of natural barriers, instead of an isolated territory, it has been a genetically porous region providing a migrational nexus to the rest of Eurasia.

Afghanistan from a Y-chromosome perspective.

Central Asia has served as a corridor for human migrations providing trading routes since ancient times. It has functioned as a conduit connecting Europe and the Middle East with South Asia and far Eastern civilizations. Therefore, the study of populations in this region is essential for a comprehensive understanding of early human dispersal on the Eurasian continent. Although Y- chromosome distributions in Central Asia have been widely surveyed, present-day Afghanistan remains poorly characterized genetically. The present study addresses this lacuna by analyzing 190 Pathan males from Afghanistan using high-resolution Y-chromosome binary markers. In addition, haplotype diversity for its most common lineages (haplogroups R1a1a*-M198 and L3-M357) was estimated using a set of 15 Y-specific STR loci. The observed haplogroup distribution suggests some degree of genetic isolation of the northern population, likely due to the Hindu Kush mountain range separating it from the southern Afghans who have had greater contact with neighboring Pathans from Pakistan and migrations from the Indian subcontinent. Our study demonstrates genetic similarities between Pathans from Afghanistan and Pakistan, both of which are characterized by the predominance of haplogroup R1a1a*-M198 (>50%) and the sharing of the same modal haplotype. Furthermore, the high frequencies of R1a1a-M198 and the presence of G2c-M377 chromosomes in Pathans might represent phylogenetic signals from Khazars, a common link between Pathans and Ashkenazi groups, whereas the absence of E1b1b1a2-V13 lineage does not support their professed Greek ancestry.

Y-STR profiling in two Afghanistan populations.

Afghanistan's unique geostrategic position in Eurasia has historically attracted commerce, conflict and conquest to the region. It was also an important stop along the Silk Road, connecting the far eastern civilizations with the western world. Nevertheless, limited genetic studies have been performed in Afghan populations. In this study, 17 Y-chromosomal short tandem repeat (Y-STR) loci were typed to evaluate their forensic and population genetic applications in 189 unrelated Afghan males geographically partitioned along the Hindu Kush Mountain range into north (N=44) and south (N=145) populations. North Afghanistan (0.9734, 0.9905) exhibits higher haplotype diversity than south Afghanistan (0.9408, 0.9813) at both the minimal 9-loci and 17-loci Yfiler haplotypes, respectively. The overall haplotype diversity for both Afghan populations at 17 Y-STR loci is 0.9850 and the corresponding value for the minimal 9-loci haplotypes is 0.9487. A query using of the most frequent Afghan Yfiler haplotype (7.98%) against the worldwide Y-STR haplotype reference database (YHRD) returned no profile match, indicating a high power of discrimination with 17 Y-STR loci. A median-joining network based on 15 Y-STR loci displays limited haplotype sharing between the two Afghan populations, possibly due to the Hindu Kush Mountain range serving as a natural barrier to gene flow between the two regions.

Insights on human evolution: an analysis of Alu insertion polymorphisms.

We analyzed the genetic profile of 563 individuals from 12 geographically targeted human populations from Europe, Asia and Africa using 27 human-specific polymorphic Alu insertions. Phylogenetic analyses indicated a clear correspondence between genetic profiles and historical patterns of gene flow and genetic drift. Sub-Saharan African populations (Benin, Cameroon, Kenya and Rwanda) formed a visibly differentiated cluster, indicating the role of the Sahara desert as a strong natural barrier to gene flow. Moreover, a higher than expected genetic affinity between populations from Europe, North Africa and Asia was detected, probably reflecting the homogenizing effects of bidirectional migratory processes between Eurasia and North Africa during the Plio-Pleistocene and Neolithic periods or the insensitivity of these markers in discriminating between these groups. The Ami aborigines of Formosa present a distinctive degree of genetic uniqueness from all the other groups, consistent with a pattern of isolation by distance, small population size and, accordingly, substantial genetic drift. We further tested all 27 Alu loci for their potential usefulness as ancestry informative markers (AIMs). On the basis of differences between weighted allelic frequencies (delta-values) and F(ST) values, we propose that 11 of the 27 Alu elements could be useful as part of the current AIM panels to assess phylogenetic relationships.

Genetic insights into the origins of Tibeto-Burman populations in the Himalayas.

The Himalayan mountain range has played a dual role in shaping the genetic landscape of the region by (1) delineating east-west migrations including the Silk Road and (2) restricting human dispersals, especially from the Indian subcontinent into the Tibetan plateau. In this study, 15 hypervariable autosomal STR loci were employed to evaluate the genetic relationships of three populations from Nepal (Kathmandu, Newar and Tamang) and a general collection from Tibet. These Himalayan groups were compared to geographically targeted worldwide populations as well as Tibeto-Burman (TB) speaking groups from Northeast India. Our results suggest a Northeast Asian origin for the Himalayan populations with subsequent gene flow from South Asia into the Kathmandu valley and the Newar population, corroborating a previous Y-chromosome study. In contrast, Tamang and Tibet exhibit limited genetic contributions from South Asia, possibly due to the orographic obstacle presented by the Himalayan massif. The TB groups from Northeast India are genetically distinct compared to their counterparts from the Himalayas probably resulting from prolonged isolation and/or founder effects.