1,721,045 research outputs found
Holocene human peopling of Libyan Sahara: molecular analysis of maternal lineages in ancient and extant populations of Fezzan
Full text linkIl presente lavoro offre un quadro descrittivo, dal punto di vista genetico, di una regione che è ancora piuttosto sconosciuta: il Sahara Centrale. Lo scopo del progetto è quello di ricostruire attraverso l’analisi del DNA mitocondriale (DNAmt) le origini di una popolazione pastorale Tuareg insediata nel Sahara libico. L’area presa in esame è quella del Fezzan, una regione nella Libia Sud-Occidentale. Per poter risalire ad una eventuale continuità genetica tra i Tuareg che oggi abitano quella regione, e i gruppi umani nomadi che in epoca preistorica occuparono quella zona, sono state effettuate analisi genetiche sia su campioni moderni che antichi, raccolti in collaborazione con la Missione Italiana Archeologica in Libia diretta dal Prof. Savino Di Lernia. Le analisi molecolari condotte sul materiale archeologico a disposizione, hanno evidenziato però il basso stato di conservazione del DNA, probabilmente dovuto alle alte temperature cui le ossa sono state sottoposte all’interno delle sepolture almeno negli ultimi 2,000 anni. Per quanto riguarda il campione moderno, un totale di 129 individui provenienti da due villaggi situati nella zona dell’Acacus, nel Fezzan, sono stati analizzati a livello del DNAmt. Il confronto con i dati genetici di popolazioni Africane attuali presenti in letteratura, e l’integrazione con dati archeologici ed etnologici, ha permesso di ricostruire le origini dei Tuareg in Libia, e di capire in che modo questi sono stati coinvolti nelle migrazioni umane che caratterizzarono il Nord Africa durante l’Olocene.
I risultati riportati nel presente studio evidenziano un livello molto basso di diversità genetica nel campione Tuareg Libico, probabilmente associato a pratiche endogamiche. Inoltre, le analisi filogenetiche indicano che il pool genetico mitocondriale dei Tuareg in Libia è caratterizzato da una componente “Eurasiatica Occidentale” predominante, che è condivisa con alcuni gruppi Berberi Nord Africani e verosimilmente proviene dalla penisola Iberica, e una componente minore di tipo “Sud-Sahariano”, che evidenzia una certa affinità con le popolazioni dell’Africa Centrale e Orientale.The present work provides an important view of a region of Africa that is still almost unknown: the Central Sahara. The aim of the project as a whole, was to reconstruct from the maternal side, through the genetic analysis of mitochondrial DNA (mtDNA), the origins of a Pastoral nomad population in the Libyan Sahara, the Tuareg. The availability of both modern and ancient samples from the Fezzan (Libyan Sahara), collected in collaboration with the Italian Archaeological Mission in Libya directed by Prof. Savino Di Lernia, represented an important means of relating the mtDNA pool of extant Libyan Tuareg, with that of Pastoral people inhabiting the Central Sahara in prehistoric times, and with the Garamantes, the hypothetical ancestors of Libyan Tuareg. Nevertheless, molecular analysis carried out on the bones collected from the archaeological sites of the Acacus region, showed a very low state of preservation of the DNA, this probably due to the high temperatures that characterised burials over the centuries. Failure of the genetic analyses in the ancient individuals, necessarily limited the present work to the study of the extant Tuareg sample. Nevertheless, comparison with other genetic data collected so far in the modern African populations, and moreover the multidisciplinary integration with archaeological and ethnological data, helped to hypothetically reconstruct the origins of Libyan Tuareg, and their relationship with the ancient human migratory dynamics that occurred in Northern Africa during the Holocene.
A total of 129 individuals from two villages in the Acacus region, in Fezzan, were genetically analysed at the mtDNA level. The results here reported clearly show the low level of genetic diversity in the Libyan Tuareg sample, that is hypothetically due to high endogamy. Furthermore, phylogenetic analyses indicate that the mtDNA genetic pool of the Libyan Tuareg is characterized by a major “West-Eurasian” component, that is shared with many Berber groups and hypothetically comes from the Iberian Peninsula, and a minor “South-Saharan” component that shows some kind of relationship with Central and Eastern African populations
The Dispersal of the Domestic Cat: Paleogenetic and Zooarcheological Evidence
Full text linkDomestication is one of the most interesting and challenging processes in human and animal evolution. The fundamental change in subsistence strategies from hunting and gathering to farming that took place for the first time in the Levant more than ten thousand years ago profoundly changed human culture and biology, and set the groundwork for population growth, migrations, the rise of civilizations, and wealth disparities (Bocquet-Appel 2011; Gignoux, Henn, and Mountain 2011; Kohler et al. 2017).status: Publishe
Mediterranean Y-chromosome 2.0why the Y in the Mediterranean is still relevant in the postgenomic era
No full textContext: Due to its unique paternal inheritance, the Y-chromosome has been a highly popular marker among population geneticists for over two decades. Recently, the advent of cost-effective genome-wide methods has unlocked information-rich autosomal genomic data, paving the way to the postgenomic era. This seems to have announced the decreasing popularity of investigating Y-chromosome variation, which provides only the paternal perspective of human ancestries and is strongly influenced by genetic drift and social behaviour.Objective: For this special issue on population genetics of the Mediterranean, the aim was to demonstrate that the Y-chromosome still provides important insights in the postgenomic era and in a time when ancient genomes are becoming exponentially available.Methods: A systematic literature search on Y-chromosomal studies in the Mediterranean was performed.Results: Several applications of Y-chromosomal analysis with future opportunities are formulated and illustrated with studies on Mediterranean populations.Conclusions: There will be no reduced interest in Y-chromosomal studies going from reconstruction of male-specific demographic events to ancient DNA applications, surname history and population-wide estimations of extra-pair paternity rates. Moreover, more initiatives are required to collect population genetic data of Y-chromosomal markers for forensic research, and to include Y-chromosomal data in GWAS investigations and studies on male infertility
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
Inter- and intraspecific variation in the surface pattern of the dermal bones of two sturgeon species
No full textArchaeological bone remains of sturgeon (Acipenser sturio/Acipenser oxyrinchus) from northwestern Europe are often identified to species on the basis of their surface morphology and then used to reconstruct the spatial distribution of the two species through time. The dermal bones of A. sturio are said to have an exterior surface pattern consisting of tubercles, while those of A. oxyrinchus are said to display alveoli. In the present paper, the validity of the surface pattern as a species-specific characteristic is critically assessed. To this purpose, dermal plates from modern, genetically identified museum specimens were studied and the surface morphology observed in a series of archaeological remains was compared with the genetic identifications obtained on these same remains. The analyses show that the surface pattern of dermal bones is related to the size of the individual, with the pattern of small A. oxyrinchus being similar to that of A. sturio. In addition, variations in the surface pattern among the bones of a single individual and within the same bone have been observed. These findings explain previous conflicting results between morphological and genetic identifications and allow the formulation of some recommendations for more accurate morphological identification of isolated archaeological sturgeon dermal bones
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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