We present a new spatially explicit computer simulation approach to estimate partial population continuity through time using ancient DNA. The approach uses a pair of genetic or genomic samples of different times but located in same area to estimate the genetic legacy of individuals belonging to the most ancient population to the most recent population. It provides a useful tool for the analysis of the numerous ancient DNA data sets that are currently being produced for many different species. We applied our original approach to the question of the Neolithic transition in Central Europe and show that a substantial proportion of genes brought by the farmers in this region were assimilated from hunter-gatherer populations during the Neolithic spread from Anatolia.
Dans la civilisation Dogon, au Mali, les animaux sont présents dès la création du monde…. Parcours dans la cosmogonie et mythologie de ce peuple animiste et artistique.
The dispersal of non-native genes due to hybridization is a form of cryptic invasion with growing concern in evolution and conservation. This includes the spread of transgenic genes and antibiotic resistance. To investigate how genes and phenotypes are transmitted in such situation, we developed a general model which includes genetic and demographic parameters and represents a powerful tool for the study of a wide range of biological and societal questions. We used this model to show that mallard ducks introduced in New Zealand benefit from hybridization to replace native grey-ducks.
En collaboration avec deux autres équipes de recherche européennes, les deux laboratoires de l'Unité d'anthropologie, l'AGP (Anthropologie, Génétique et Peuplements) et l'APA (Archéologie et Peuplement de l'Afrique) viennent de publier ensemble un article de revue sur l'histoire génétique des populations africaines du Sahel.
In collaboration with two other European research groups, the two laboratories of the Anthropology Unit, AGP (Anthropology, Genetics and Peopling history) and APA (Archaeology and African peopling) have just published a Review paper on the Genetic history of the African Sahelian population.
The group of Alicia Sanchez-Mazas identified two HLA-B alleles as candidates to Plasmodium falciparum malaria protection in Africa. Their study, published on October 16th, 2017 in Molecular Ecology, suggested that these alleles, which share close peptide-binding profiles, became beneficial at the onset of this disease. Pathogen-driven selection in the form of soft selective sweep thus likely contributed to shape the HLA-B genetic landscape of Africa.
Des chercheurs de l’Institut Max Planck ont procédé à l'analyse génétique d’une néandertalienne qui vivait sur le territoire de la Croatie actuelle il y a 52'000 ans. Cette recherche, publiée dans la revue "Science", apporte de nouvelles connaissances sur le mode de vie de nos cousins d'humanité.
Les explications d'Alicia Sanchez-Mazas, responsable de l'Unité d'anthropologie du Département de génétique et évolution de l'Université de Genève, interrogée par Sarah
Le pays Dogon est une région du Mali qui se situe au sud-ouest de la boucle du Niger.
Le site des falaises de Bandiagara est depuis 1989, inscrit sur la liste du patrimoine mondial de lʹUnesco.
Avec Eric Huysecom, anthropologue et archéologue, directeur du Laboratoire d'Archéologie et Peuplement de lʹAfrique du Département de génétique et évolution de lʹUniversité de Genève.
Depuis les années 70-80, les demandes de restitutions auprès des musées français, britanniques, allemands, se sont multipliées. Le Benin, le Mali, le Nigéria, la Chine, des pays qui demandent la récupération des œuvres spoliées par les ex-puissances coloniales. A quelles conditions?
Le Dr Mathias Currat s'exprime à la radio dans le cadre de la 17e édition du colloque Wright qui a pour thématique "La génomique, soit l’étude du fonctionnement de la vie à l’échelle du génome. En d’autres termes, le mode d’emploi du vivant”.
The main function of HLA class I molecules is to present pathogen-derived peptides to cytotoxic T lymphocytes. This function is assumed to drive the maintenance of an extraordinary amount of polymorphism at each HLA locus, providing an immune advantage to heterozygote individuals capable to present larger repertories of peptides than homozygotes.
Prof. Alicia Sanchez-Mazas was appointed Section Editor of HLA (previously Tissue Antigens), the official journal of the European Federation for Immunogenetics (EFI), and is in charge of the “HLA polymorphism in populations” Section.
Dietary changes associated to shifts in subsistence strategies during human evolution may have induced new selective pressures on phenotypes, as currently held for lactase persistence. Similar hypotheses exist for arylamine N-acetyltransferase 2 (NAT2) mediated acetylation capacity, a well-known pharmacogenetic trait with wide inter-individual variation explained by polymorphisms in the NAT2 gene.
Recent genetic studies have suggested that the colonization of East Asia by modern humans was more complex than a single origin from the South, and that a genetic contribution via a Northern route was probably quite substantial.
We extend the scope of European palaeogenomics by sequencing the genomes of Late Upper Palaeolithic (13,300 years old, 1.4-fold coverage) and Mesolithic (9,700 years old, 15.4-fold) males from western Georgia in the Caucasus and a Late Upper Palaeolithic (13,700 years old, 9.5-fold) male from Switzerland.
Supertypes are groups of human leukocyte antigen (HLA) alleles which bind overlapping sets of peptides due to sharing specific residues at the anchor positions—the B and F pockets—of the peptide-binding region (PBR). HLA alleles within the same supertype are expected to be functionally similar, while those from different supertypes are expected to be functionally distinct, presenting different sets of peptides. In this study, we applied the supertype classification to the HLA-A and HLA-B data of 55 worldwide populations in order to investigate the effect of natural selection on supertype rather than allelic variation at these loci.
Publié avec l'appui de l'Office Fédéral de la Culture (OFC), de l'Académie Suisse des Sciences Humaines et Sociales (ASSH) et du Laboratoire Archéologie et Peuplement de l'Afrique (APA) de l'Université de Genève.
Le professeur Eric Huysecom parle de Djenné, l'une des villes les plus célèbres du Mali. Habitée depuis 250 av J.C, elle s'est développée pour devenir un marché de référence et une ville importante pour le commerce transsaharien.
La professeure Alicia Sanchez-Mazas nous éclaire sur l'affirmation de chercheurs américains selon laquelle, nous aurions tous tendance, inconsciemment, à choisir comme amis des individus génétiquement proches de nous.
HLA genes are highly polymorphic in human populations as a result of diversifying selection related to their immune function. However, HLA geographic variation worldwide suggests that demographic factors also shaped their evolution. We here analyzed in detail HLA genetic variation in Europe in order to identify signatures of migration history and/or natural selection.
The genetic diversity of Europeans has been shaped by various evolutionary forces including their demographic history. Genetic data can thus be used to draw inferences on the population history of Europe using appropriate statistical methods such as computer simulation, which constitutes a powerful tool to study complex models.
Explaining the genetic diversity of past and present European populations. Although it is the continent with the lowest genomic diversity, Europe embraces a significant degree of variation, shaped by complex demographic events and locus-specific selective factors linked to environmental conditions. The European genetic diversity observed today has also important clinical and epidemiological implications. Different questions related to these topics are addressed in this special topic issue of eight excellent papers written by specialized European teams. The papers document the remarkable progress achieved in the last years in exploring human genomic diversity, both in past and present populations, in reconstructing complex scenarios of European peopling history using sophisticated data analyses and computer simulations, in identifying signatures of adaptive selection in milk digestion- and immune-related genes, and in applying this knowledge to crucial health issues, from tissue transplantation to disease associations.
Le Dr Mathias Currat s'exprime sur “une méthode génétique développée par des chercheurs de l’université de Sheffield en Grande-Bretagne qui permettrait de déterminer les origines géographiques d'une personne, il y a mille ans”.
The emergence and evolution of social complexity remains a major topic in African later prehistory. This paper aims to examine this question in the Dogon Country in Mali by reassessing the chronocultural sequence of Toloy-Tellem-Dogon that was defined 40 years ago. Our discovery of two new sites on the Bandiagara Escarpment with coiled clay tombs (Dourou-Boro and Yawa-vaches), the systematic dating of these structures, the re-analysis of similar buildings in Pégué, as well as the establishment of a typol- ogy of architectural techniques, led us to propose a continuous chronocultural evolution for these struc- tures, now considered to be primary burials and not granaries, over about 1800 years. Detailed study of the ceramics also indicates the evolution of local traditions, progressively integrating new elements fol- lowing many contacts with neighboring regions during the 1st millennium AD. Finally, the chemical anal- ysis of the glass beads discovered in Dourou-Boro shows that these societies were using beads made in the Middle East at least from the last quarter of the 1st millennium AD on. The new data presented in this article highlight, on one hand, the originality, antiquity, and longevity of burial practices indicating a strong local cultural identity, and, on the other hand, the participation of pre-Dogon populations (long reputed for being isolated from the outside world) in broader African socioeconomic dynamics.
Alicia Sanchez-Mazas is the partner for the University of Geneva of the FP7-Health program EUROSTAM, which has been supported by a € 2.6 million grant. The main objective of the three year project is to determine the feasibility and advantage of implementing a Europe-wide acceptable mismatch program to facilitate transplantation of highly sensitized patients all over Europe. Sanchez-Mazas’ group is involved as an expert of HLA molecular diversity in human populations, with a main participation to the definition of a new epitope-based matching programme.
Que peuvent nous apprendre les fouilles d’Ounjougou au Mali ? Une histoire bien différente de celle que nous connaissons, ou du moins, que nous supposons. Homme de terrain et théoricien de l’archéologie, Eric Huysecom, œuvre depuis 25 ans à comprendre l'histoire du peuplement humain de l’Afrique. Il vient de découvrir, que, bien avant l’Europe, les populations d’Afrique de l’Ouest, invente le Néolithique et, avec celui-ci, un cortège de nouveautés. C’était il y a 11400 ans…
The forensic genetics field is generating extensive population data on polymorphism of short tandem repeats (STR) markers in globally distributed samples. In this study we explored and quantified the informative power of these datasets to address issues related to human evolution and diversity, by using two online resources: an allele frequency dataset representing 141 populations summing up to almost 26 thousand individuals; a genotype dataset consisting of 42 populations and more than 11 thousand individuals.
“Alicia Sanchez-Mazas mène dans son laboratoire de l’Université de Genève des études sur la diversité génétique humaine. Son objectif : mieux comprendre l’histoire du peuplement et briser certaines conceptions dépassées sur l’espèce humaine”.
Portrait du Professeure Alicia Sanchez-Mazas dans l'édition de novembre de la revue La Recherche.
This study aims at investigating the HLA molecular variation across Switzerland in order to determine possible regional differences, which would be highly relevant to several purposes: optimizing donor recruitment strategies in hematopoietic stem cell transplantation (HSCT), providing reliable reference data in HLA and disease association studies, and understanding the population genetic background(s) of this culturally heterogeneous country. More…HLA molecular data of more than 20,000 HSCT donors from 9–13 recruitment centers of the whole country were analyzed. Allele and haplotype frequencies were estimated by using new computer tools adapted to the heterogeneity and ambiguity of the data. Non-parametric and resampling statistical tests were performed to assess Hardy-Weinberg equilibrium, selective neutrality and linkage disequilibrium among different loci, both in each recruitment center and in the whole national registry. Genetic variation was explored through genetic distance and hierarchical analysis of variance taking into account both geographic and linguistic subdivisions in Switzerland. The results indicate a heterogeneous genetic makeup of the Swiss population: first, allele frequencies estimated on the whole national registry strongly deviate from Hardy-Weinberg equilibrium, by contrast with the results obtained for individual centers; second, a pronounced differentiation is observed for Ticino, Graubünden, and, to a lesser extent, Wallis, suggesting that the Alps represent(ed) a barrier to gene flow; finally, although cultural (linguistic) boundaries do not represent a main genetic differentiation factor in Switzerland, the genetic relatedness between population from south-eastern Switzerland and Italy agrees with historical and linguistic data. Overall, this study justifies the maintenance of a decentralized donor recruitment structure in Switzerland allowing increasing the genetic diversity of the national—and hence global—donor registry. It also indicates that HLA data of local donor recruitment centers can be used as reference data in both epidemiological and population genetic studies focusing on the genetic history of present European populations.
Human leucocyte antigen (HLA) loci have a complex evolution where both stochastic (e.g. genetic
drift) and deterministic (natural selection) forces are involved. Owing to their extraordinary level of
polymorphism, HLA genes are useful markers for reconstructing human settlement history. However,
HLA variation often deviates significantly from neutral expectations towards an excess of
genetic diversity. More…Because HLA molecules play a crucial role in immunity, this observation is generally
explained by pathogen-driven-balancing selection (PDBS). In this study, we investigate the
PDBS model by analysing HLA allelic diversity on a large database of 535 populations in relation
to pathogen richness. Our results confirm that geographical distances are excellent predictors of
HLA genetic differentiation worldwide. We also find a significant positive correlation between genetic
diversity and pathogen richness at two HLA class I loci (HLA-A and -B), as predicted by
PDBS, and a significant negative correlation at one HLA class II locus (HLA-DQB1). Although
these effects are weak, as shown by a loss of significance when populations submitted to rapid genetic
drift are removed from the analysis, the inverse relationship between genetic diversity and
pathogen richness at different loci indicates that HLA genes have adopted distinct evolutionary
strategies to provide immune protection in pathogen-rich environments.
The question of links between material cultural and sociocultural meaning remains a challenge in archaeology. In this book, Anne Mayor proposes a tool for archaeological interpretation in the area of ceramic studies, capable of addressing questions of ethnolinguistic identity and the settlement history in the Niger Bend, West Africa.
