1,721,047 research outputs found
Timing the first human migration into eastern Asia
No full textAbstract A recent report in BMC Biology indicates that modern humans first arrived in southern East Asia 60,000 years ago and settled the rest of East Asia from there. This early date and migration route has significant implications for our understanding of the origins of present-day human populations.</p
Polymorphic transposable elements provide new insights on high-altitude adaptation in the Tibetan Plateau
Full text linkSeveral studies demonstrated that populations living in the Tibetan plateau are genetically and physiologically adapted to high-altitude conditions, showing genomic signatures ascribable to the action of natural selection. However, so far most of them relied solely on inferences drawn from the analysis of coding variants and point mutations. To fill this gap, we focused on the possible role of polymorphic transposable elements in influencing the adaptation of Tibetan and Sherpa highlanders. To do so, we compared high-altitude and middle/low-lander individuals of East Asian ancestry by performing in silico analyses and differentiation tests on 118 modern and ancient samples. We detected several transposable elements associated with high altitude, which map genes involved in cardiovascular, hematological, chem-dependent and respiratory conditions, suggesting that metabolic and signaling pathways taking part in these functions are disproportionately impacted by the effect of environmental stressors in high-altitude individuals. To our knowledge, our study is the first hinting to a possible role of transposable elements in the adaptation of Tibetan and Sherpa highlanders
Exploring genetic variability of genes involved in nutrition and thermoregulation processes in european populations
No full textEnvironmental and cultural changes, such as those affecting dietary habits, are known to have substantially affected populations’ allele frequencies over human evolutionary history, triggering several adaptive processes. In some cases, especially since the Neolithic transition, they were established so rapidly to prevent adequate genetic adaptation to new nutritional/ecological conditions, thus potentially leading to various common chronic diseases. To detect genetic signatures of some of these evolutionary events and taking advantage from the 1000Genomes project dataset, we have analysed patterns of variation at a set of genes involved in nutritional and thermogenesis processes. Our preliminary results indicate PRDM16, a gene involved in the development of brown and beige adipocytes, as the most polymorphic locus within Europe. For instance, clusters and FST analyses pointed out completely different patterns between northern and southern European populations, suggesting the plausible action of climatic selective pressures on this gene. This study was conducted within the framework of the EPIC project (PRIN2012)
Investigating the link between past adaptations and modern diseases: a nutrition-related perspective
No full textA string of biological and cultural changes strongly related to the occupation of new environmental contexts has characterized the evolution of the human lineage, especially during the widespread colonization of non-African continents by anatomically modern humans. Therefore, geographically and temporally defined variation of selective pressures acting on the genomes of both H. sapiens ancestors and modern populations triggered genetic adaptations in response to local environments.
In particular, necessity to cope with unprecedented nutritional landscapes prompted a number of biological shifts in many human groups, mainly related to the introduction of considerable modifications of their diets and of new challenges to their metabolism [1,2], contributing to influence a variety of traits, among which differential disease susceptibility of human populations due to possible maladaptive processes [3].
In fact, the rate of dietary changes dramatically increased in the very recent evolutionary history of our species, as a consequence of introduction of agricultural and pastoralist practices, of consumption of industrial refined foods and of ever-increasing globalization [4], thus potentially converting some adaptive traits into maladaptive ones. In accordance to this view, increasing discordance between our anciently determined biology and contemporary nutritional or cultural patterns is supposed to have contributed to the spread of several complex diseases, which may represent by-products of past adaptive events due to loci that have become detrimental in modern societies [5].
To test this hypothesis, we have investigated the genetic legacy of natural selection on a panel of about one hundred genes representative of the main players driving functional pathways associated to food digestion and energy balance, or which turned out to be altered in metabolic and nutrition-related diseases. Sequence data for human populations living in different biomes were collected from public databases and used, in combination with unpublished data on individuals affected by certain nutrition-related diseases, to explore patterns of variation at more than 100,000 single nucleotide variants and/or indels. Population differentiation analyses based on the calculation of pairwise Fst indices among genetically homogeneous clusters of populations and on their comparison with genome-wide Fst distributions pointed out a few genes unusually differentiated with respect to average genomic patterns. Haplotype structure and potential deviations from a neutral model of evolution were then investigated at these candidate regions by applying several neutrality tests and by performing calibrated coalescent simulations, to disentangle the interplay between natural selection, demographic events and local mutation/recombination rates in shaping the observed patterns of variation. This enabled to elucidate implications of loci responsible for past adaptive events in the examined diseases, contributing to explain their underlying mechanisms and present-day epidemiological patterns, as well as some of the evolutionary processes that made our genome prone to the side effects of modern environmental stimuli
From the Alps to the Mediterranean and beyond: genetics, environment, culture and the "impossible beauty" of Italy
Full text linkSince prehistoric times, Italy has represented a bridge between peoples, genes and cultures. Its peculiar geographical position explains why: it is located in the center of the Mediterranean Sea, flanked by the Balkans and the Hellenic Peninsula to the east, Iberia to the west and surrounded by North Africa to the south and central Europe to the north. This makes Italy of extraordinary interest for the study of some different aspects of human diversity. Here we overview current knowledge regarding the relationships between the structure of the genetic variation of Italian populations and the geographical, ecological and cultural factors that have characterized their evolutionary history. Human presence in Italian territory is deeply rooted in the past. Lithic artifacts produced by the genus Homo and remains of Homo sapiens are among the earliest to have been found on the continent, as shown by the lithic industry of Pirro Nord (between 1.3 and 1.6 Mya) and the dental remains of the "Grotta del Cavallo" (between 45 and 43 Kya). Genetic and genomic studies relating to existing and extinct human groups have shed light on the migrations from Europe, Africa and Asia that created the ancient layers of the genetic structure of today's Italian populations, especially before the Iron Age. The important role of isolation (genetic and cultural) in shaping genetic structure is clearly visible in the patterns of intra- and inter-population diversity observed among Italian ethno-linguistic minorities that settled on the peninsula and on the major islands until the 19th century. Finally, selective pressures have likely driven the distribution of originally adaptive variants and haplotypes that now confer protection or susceptibility to major diseases such as diabetes and cardiovascular disease (in northern Italy) and tuberculosis and leprosy (in the south). What emerges is a picture where the combined effects of migration, isolation and natural selection generated by the interplay of geography, environment and culture have shaped a complex pattern of human diversity that is unique in Europe and which goes hand in hand with today's rich animal and plant biodiversity. In a nutshell, scientific evidence and cultural heritage paint Italy as a place with extremely diverse environments where distant peoples have met since the deep past, bringing and sharing genes and ideas
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Multiple selective events at the PRDM16 functional pathway shaped adaptation of western European populations to different climate conditions
Full text linkSeveral studies highlighted the role of climate in shaping many human evolutionary processes. This occurred even in relatively recent times, having affected various human phenotypic traits, among which metabolic processes that orchestrate absorption and accumulation of substances to maintain energy homeostasis, that is critical for the survival of individuals in high energy-expenditure environments. To date, most researches have focalized on detection of climatic influence on SNPs' frequency in populations exposed to extreme environmental conditions or by comparing variation patterns between populations from different continents. In this study, we instead explored the genetic background of distinct western European human groups at loci involved in nutritional and thermoregulation processes, to test whether patterns of differential local adaptation to environmental conditions could be appreciated also at a lower geographical scale. Taking advantage from the 1000 Genomes Project data, genetic information for 21 genes involved in nutritional and thermoregulation processes was analysed for three western European populations. The applied Anthropological Genetics methods pointed to appreciable differentiation between the examined groups especially for the PRDM16 gene. Moreover, several neutrality tests suggested that balancing selection has acted on different regions of the gene in people from Great Britain, as well as that more recent positive selection could have also targeted some PRDM16 SNPs in Finn and Italian populations. These series of adaptive footprints are plausibly related to climate variability in both ancient and relatively recent times. Since this locus is involved in thermoregulation mechanisms and adipogenesis, local adaptations mediated by a pathway related to the brown adipose tissue activity could have evolved in response to changing cold temperature exposures of such populations
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