@article {8351, title = {Global diversity in the TAS2R38 bitter taste receptor: revisiting a classic evolutionary PROPosal.}, journal = {Sci Rep}, volume = {6}, year = {2016}, month = {2016}, pages = {25506}, abstract = {

The ability to taste phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) is a polymorphic trait mediated by the TAS2R38 bitter taste receptor gene. It has long been hypothesized that global genetic diversity at this locus evolved under pervasive pressures from balancing natural selection. However, recent high-resolution population genetic studies of TAS2Rs suggest that demographic events have played a critical role in the evolution of these genes. We here utilized the largest TAS2R38 database yet analyzed, consisting of 5,589 individuals from 105 populations, to examine natural selection, haplotype frequencies and linkage disequilibrium to estimate the effects of both selection and demography on contemporary patterns of variation at this locus. We found signs of an ancient balancing selection acting on this gene but no post Out-Of-Africa departures from neutrality, implying that the current observed patterns of variation can be predominantly explained by demographic, rather than selective events. In addition, we found signatures of ancient selective forces acting on different African TAS2R38 haplotypes. Collectively our results provide evidence for a relaxation of recent selective forces acting on this gene and a revised hypothesis for the origins of the present-day worldwide distribution of TAS2R38 haplotypes.

}, issn = {2045-2322}, doi = {10.1038/srep25506}, author = {Risso, Davide S and Mezzavilla, Massimo and Pagani, Luca and Robino, Antonietta and Morini, Gabriella and Tofanelli, Sergio and Carrai, Maura and Campa, Daniele and Barale, Roberto and Caradonna, Fabio and Gasparini, Paolo and Luiselli, Donata and Wooding, Stephen and Drayna, Dennis} } @article {8069, title = {Genetic evidence for an origin of the Armenians from Bronze Age mixing of multiple populations.}, journal = {Eur J Hum Genet}, year = {2015}, month = {2015 Oct 21}, abstract = {

The Armenians are a culturally isolated population who historically inhabited a region in the Near East bounded by the Mediterranean and Black seas and the Caucasus, but remain under-represented in genetic studies and have a complex history including a major geographic displacement during World War I. Here, we analyse genome-wide variation in 173 Armenians and compare them with 78 other worldwide populations. We find that Armenians form a distinctive cluster linking the Near East, Europe, and the Caucasus. We show that Armenian diversity can be explained by several mixtures of Eurasian populations that occurred between ~3000 and ~2000 bce, a period characterized by major population migrations after the domestication of the horse, appearance of chariots, and the rise of advanced civilizations in the Near East. However, genetic signals of population mixture cease after ~1200 bce when Bronze Age civilizations in the Eastern Mediterranean world suddenly and violently collapsed. Armenians have since remained isolated and genetic structure within the population developed ~500 years ago when Armenia was divided between the Ottomans and the Safavid Empire in Iran. Finally, we show that Armenians have higher genetic affinity to Neolithic Europeans than other present-day Near Easterners, and that 29\% of Armenian ancestry may originate from an ancestral population that is best represented by Neolithic Europeans.European Journal of Human Genetics advance online publication, 21 October 2015; doi:10.1038/ejhg.2015.206.

}, issn = {1476-5438}, doi = {10.1038/ejhg.2015.206}, author = {Haber, Marc and Mezzavilla, Massimo and Xue, Yali and Comas, David and Gasparini, Paolo and Zalloua, Pierre and Tyler-Smith, Chris} } @article {3622, title = {Genetic landscape of populations along the Silk Road: admixture and migration patterns.}, journal = {BMC Genet}, volume = {15}, year = {2014}, month = {2014}, pages = {131}, abstract = {

BACKGROUND: The ancient Silk Road has been a trading route between Europe and Central Asia from the 2(nd) century BCE to the 15(th) century CE. While most populations on this route have been characterized, the genetic background of others remains poorly understood, and little is known about past migration patterns. The scientific expedition "Marco Polo" has recently collected genetic and phenotypic data in six regions (Georgia, Armenia, Azerbaijan, Uzbekistan, Kazakhstan, Tajikistan) along the Silk Road to study the genetics of a number of phenotypes.

RESULTS: We characterized the genetic structure of these populations within a worldwide context. We observed a West-East subdivision albeit the existence of a genetic component shared within Central Asia and nearby populations from Europe and Near East. We observed a contribution of up to 50\% from Europe and Asia to most of the populations that have been analyzed. The contribution from Asia dates back to ~25 generations and is limited to the Eastern Silk Road. Time and direction of this contribution are consistent with the Mongolian expansion era.

CONCLUSIONS: We clarified the genetic structure of six populations from Central Asia and suggested a complex pattern of gene flow among them. We provided a map of migration events in time and space and we quantified exchanges among populations. Altogether these novel findings will support the future studies aimed at understanding the genetics of the phenotypes that have been collected during the Marco Polo campaign, they will provide insights into the history of these populations, and they will be useful to reconstruct the developments and events that have shaped modern Eurasians genomes.

}, keywords = {Asian Continental Ancestry Group, Commonwealth of Independent States, European Continental Ancestry Group, Gene Flow, Homozygote, Human Migration, Humans, Phenotype, Polymorphism, Single Nucleotide, Principal Component Analysis, Sequence Analysis, DNA}, issn = {1471-2156}, doi = {10.1186/s12863-014-0131-6}, author = {Mezzavilla, Massimo and Vozzi, Diego and Pirastu, Nicola and Girotto, Giorgia and d{\textquoteright}Adamo, Pio and Gasparini, Paolo and Colonna, Vincenza} }