Results

In general, the BIOSTRE project showed that the genetic variation among populations from Trentino is greater than that observed among the same number of European populations coming from geographically distant areas. This result shows that even in a small area such as Trentino, human genetic variation is appreciable even if only in relative terms. In fact, the absolute value  is very low (~1%) if one considers that overall, the European population is genetically homogeneous. The genetic variation in all populations, comprising those from Trentino, is mostly present within the same (>90%) rather than different populations.  

Moreover, in reference to the first aim of the project, the research evidenced that the high genetic variation among populations from Trentino cannot¬† simply be related to their cultural diversity. In fact, the comparison between genetic and linguistic variation represented by three principal groups [(Italian, Ladin and Cimbro) or by six different dialectal groups (Fassa V: Ladino; Non and Sole V: semi-Ladino; Giudicarie V: dialetti occidentali; Primiero and Fersina V: dialetto orientale; FiemmeV: dialetto dell’Avisio and, finally, Adige V: dialetto centrale, as suggested by Bertoluzza in 1991)] showed that there is no clear relation between genes and languages.¬†Furthermore, the German-speaking group of Cimbri from Luserna shows considerable genetic differentiation not only in comparison to the other groups from Trentino but also compared to other European populations, including those from Bavaria, which have a similar origin and language.¬†Moreover, the other linguistic minority, the Ladin from the Fassa valley, are genetically similar, especially at mitochondrial DNA level, to the Italian-speaking populations from Trentino. The Ladins show higher genetic affinity with the neighboring community from the Fiemme valley. This fact can be inferred, for example, from the higher number of shared genetic lines (haplotypes) among individuals from the two communities.¬† However, the highest level of sharing was observed among populations from the Non and Sole valleys, while the community from the Fersina Valley (S.Orsola terme) has no shared haplotype with any of the other populations analyzed.¬†¬†

Furthermore, regarding the above-mentioned Ladin, the comparison between the results obtained from the BIOSTRE project with those available from the literature concerning the other Ladin groups from the Gardena and Badia valleys (South Tyrol; Thomas et al., 2008) and Colle Santa Lucia (Veneto; Vernesi et al., 2002) might it possible to better clarify the genetic relationships within the Dolomite Ladin group. The research evidenced high genetic heterogeneity among communities from different geographic areas, especially for the maternally transmitted marker. This confirms the data from Thomas and collaborators.   On the other hand, in the population from Fassa valley, we evidenced some Y chromosome lineages that are rare or absent in other Trentino and European populations. Unfortunately, it  was not possible to assess the presence of these lineages in the other Ladin groups due to the low  level of resolution of the comparison data.  Further investigations will be necessary in order to established if those variants are exclusive to the Ladin from Trentino or if they are also present in the other Ladin Dolomite groups.  

Another significant result of the BIOSTRE project regarded the relation between the genetic structure of populations from Trentino and geography (object 1). The genetic and geographic distances between populations were compared. The latter were calculated not simply as linear distances but  as distances (in Km) of the shortest and easiest walking routes between one location and another chosen taking into account the presence of any natural barriers (e.g. mountain, rivers, etc..). This comparison revealed that there is no significant correlation between them and that geographic distance did not affect the genetic relationships between populations. However, estimates of principal demographic parameters ( e.g. mismatch distribution, effective population size and growth rate) might it possible  to highlight that geography played an important role in shaping the genetic structure of populations of Trentino and in their demographic history. In fact, populations  from the west-central area (the Non, Sole, Giudicarie and Adige valleys) showed clear signs of growth and demographic expansion, while those from the eastern area (the Fassa, Fiemme, Primiero, and to a greater extent Fersina valleys and Luserna plateau) show a more limited demographic growth  over time.  The population from the Adige valley showed the most marked signs of demographic growth, a fact that was also accompanied by an high genetic variation. These results are  consistent with archaeological and historical data that tell the story of an area (western-central)  that has been more densely populated since ancient times. This could be related to the geo-morphological characteristics of the territory. In fact, the west-central zone has more favorable areas for human settlement with lands which are suitable for the agriculture practices and which have important communication routes such as the Adige valley and the Garda lake. Moreover, the Adige valley has always been a sort of corridor between the various communities.

Finally, another noteworthy result regards the population of Cimbri from Luserna. This community shows, as already mentioned,¬† a marked genetic differentiation compared to all the other populations used in our comparison. Furthermore,¬† the Cimbri show the lowest genetic diversity values, which is more evident for the paternally transmitted markers. In fact, the Y-chromosome variation is represented by only three genetic lines belonging mostly to the same haplogroup (R1b) and corresponding to three different surnames. Furthermore, at mitochondrial DNA level, the Cimbri show some haplogroups with markedly high frequencies compared to other populations (e.g. H6 and K1) while other very common European haplogroups are absent (e.g H1 and H3).¬†Altogether, the genetic results seem to suggest that the Cimbri community experienced the so-called “founder effect‚ÄĚ, which is a strong form of genetic drift. This effect leads to the birth of a new population, starting from another larger and more variable, which is formed from a small number of individuals that carry only a portion of the original genetic variability. It has especially affected the male part of the population from Luserna. The comparison between genetic, demographic, historical and linguistic data on the community from Luserna has made it possible to confirm this hypothesis (Moz, 2001; Gamillscheg, 1912).

In reference to the second aim of the project, the analysis of the mitochondrial haplogroups evidenced that the populations from Trentino have retained an ancient European genetic substrate. This is testified by the presence in their gene pool of mainly haplogroups (~ 55%) that have been associated with the first settlement in Europe of Asian populations (e.g. U5 haplogroup; early Paleolithic, 45,000 years ago; Soares et al. 2010) and European groups from glacial refuges in western and eastern Europe (e.g. H1 and H3, Mesolithic, 11,000 years ago, Soares et al. 2010).¬†¬†On the other hand, the analysis evidenced a scarce presence of mitochondrial haplogroups associated with the Neolithic period (e.g. J2a, ~8,000 years ago; Soares et al., 2010). In fact, these¬† have only been sporadically¬† found in Trentino.¬† The age estimates of principal haplogroups suggest that these lineages began¬† to expand in Trentino in ancient times rather than in more recent migration events (e.g. H1 started to expanded at least 10991¬Ī 2550 years ago; H3 11721¬Ī 5146).¬† In general, these results are also confirmed at Y-chromosome level. However, currently, the origin (Neolithic rather than Paleolithic) of some principal European Y-chromosome haplogroups is controversial so it is not possible, at the moment, to draw any conclusions based on the results obtained for this marker. Overall, these results favor the hypothesis of genetic continuity between modern and pre-neolithic local populations. This suggests that the introduction of agricultural practices in the region¬† (Neolithization) could have occurred through a process of acculturation of local Mesolithic populations, rather than by the arrival of Neolithic groups, as suggested by the archaeological data in loco (Lanzinger et al., 2000).

The results obtained from the study of genetic variation in modern populations were confirmed by ancient DNA analysis.¬† In fact, data from the analysis of human remains belonging to individuals which¬† lived in the region during the Neolithic times and that were discovered in the necropolis ‚ÄúLa Vela‚ÄĚ of Trento,¬† evidenced genetic variants that are also common in other populations from Trentino and Europe.¬†However, additional data from a greater number of fossil remains will be needed to confirm these preliminary results and to clarify this important phase of prehistory of Trentino and, more in general, in Europe.¬†¬†¬†

Basic bibliography

Lanzinger M., Marzatico F., Pedrotti A. 2000. Storia del Trentino; La preistoria e la protostoria, Società editrice il Mulino, Bologna.

Cavada E. 2000. Storia del Trentino; L’età romana, Vol II. Il territorio: popolamento, abitati, necropoli. Società editrice il MulinoBologna.

Moz N.A. 2001. Luserna. Terra di uomini liberi. Rovereto: Osiride.

Soraes et al., 2010. The Archaeogenetics of Europe. Curr Biol. 23: 20(4):174-83. Review.