The genetic make-up of human beings is a result of their biological evolution and it is also influenced by geographical and socio-cultural factors such as environmental features and marriage customs. This is the outcome of a study by the EURAC Institute for Mummies and the Iceman carried out with the Department of Environmental Biology of the University of Rome "La Sapienza," which reconstructed the genetic structure of the populations of the eastern Italian Alps on the basis of bio-molecular analyses. The results of the research are now published in the scientific review Plos One.
The research group, co-ordinated by Valentina Coia, an anthropologist and expert in population genetics at EURAC, analyzed the Y-Chromosome, the paternal transmitted line, in over 15 populations of the three main ethno-linguistic groups of the eastern Italian Alps: Italians, Ladins and the German-speaking linguistic minorities of the regions of Trentino (the Cimbri of Luserna), Veneto (the Cimbri of Giazza and the community of Sappada) and Friuli (the communities of Sauris and Timau). The analysis focused on the genetic variations within these Alpine groups, on the differences between them and on comparisons with other European populations. To further explore the alpine genetic structure the Y-Chromosomal results were compared with mitochondrial DNA data, the maternal transmitted line. "In order to detect the genetic variation, we examined the differences in the genetic heritage among different populations. The human species is essentially homogeneous from a genetic perspective, however, the various groups have some subtle but significant differences at statistical and scientific level that have developed over time due to the effect of geographical, demographic and cultural factors " says Valentina Coia.
Differences related to the demographic history
The study of the Y-Chromosomal variation showed the presence of three genetic patterns: that of the more genetically homogenous Italian group, that of the Ladins with intermediate genetic differentiation values, and that of the German-speaking minorities, which were most differentiated. These results reflect the differing demographic histories of the three groups and their various levels of genetic isolation due to the mountainous environment. The greater homogeneity of the Italians could be ascribed to their ancient common origin, but also to a greater mobility and gene exchange between the populations of the seven valleys considered (the Adige, Fersina, Fiemme, Giudicarie, Non, Primiero and Sole valleys), with this mobility favored by a less hostile mountain environment (i.e. lower altitudes and geographical proximity) compared to the Ladin populations of the Dolomites. The Ladin group, despite its common origins and language, shows an high internal genetic differentiation. This may have been caused by the strong geographical isolation, but also by the process of fragmentation affecting these communities over time, first by Latin and then by Germanic peoples. The marked genetic differentiation of the communities in the German-speaking islands can also be traced back to their different demographic histories. These communities, which reached the Alpine territories only in the Middle Ages, originated from small groups, sometimes even from single families of various origins, and since their foundation they have maintained a relative geographical and cultural isolation.
Differences related to cultural traditions
The research group co-ordinated by EURAC Institute for Mummies and the Iceman also compared the results of the Y chromosome (paternal) DNA with those of the mitochondrial (maternal) DNA. The comparison considered data from the three Alpine groups, other European populations from mountainous areas, and published data from the German-speaking populations of South Tyrol. The comparison revealed that the German-speaking groups from South Tyrol shows considerably less diversity for the paternally transmitted markers, while those inherited from the mother are relatively high. "The interesting fact is that this genetic model is the opposite of that observed in the majority of European populations, including mountain populations. At the moment the most plausible interpretation is that the old South Tyrolean tradition of the Geschlossener Hof or "closed holding" [i.e. farms that are indivisible for inheritance purposes] has over the years promoted male mobility between the populations of the valleys. In fact, since males who were not firstborn would not inherit their parents' farm, they would be encouraged to leave their place of origin and this would have caused a continuous genetic exchange between groups and, over time, the development of a genetic homogeneity for the males transmitted markers. This is in contrast to the norm in most European populations where it is usually the woman who has to move. This hypothesis represents a new and original case study that helps us to understand the impact of culture-factors on the genetic make-up of human populations and on our DNA," concludes Valentina Coia.
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