Pax Augusta
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Y-chromosome variability and genetic history of Commons from Northern Italy
Stefania Sarno, Rajiv Boscolo Agostini, Sara De Fanti, Gianmarco Ferri, Silvia Ghirotto, Giorgia Modenini, Davide Pettener, Alessio Boattini
First published: 10 May 2021 https://doi.org/10.1002/ajpa.24302
Abstract
Objectives
Genetic drift and admixture are driving forces in human evolution, but their concerted impact to population evolution in historical times and at a micro-geographic scale is poorly assessed. In this study we test a demographic model encompassing both admixture and drift to the case of social-cultural isolates such as the so-called “Commons.”
Materials and methods
Commons are peculiar institutions of medieval origins whose key feature is the tight relationship between population and territory, mediated by the collective property of shared resources. Here, we analyze the Y-chromosomal genetic structure of four Commons (for a total of 366 samples) from the Central and Eastern Padana plain in Northern Italy.
Results
Our results reveal that all these groups exhibit patterns of significant diversity reduction, peripheral/outlier position within the Italian/European genetic space and high frequency of Common-specific haplogroups. By explicitly testing different drift-admixture models, we show that a drift-only model is more probable for Central Padana Commons, while additional admixture (~20%) from external population around the same time of their foundation cannot be excluded for the Eastern ones.
Discussion
Building on these results, we suggest central Middle Ages as the most probable age of foundation for three of the considered Commons, the remaining one pointing to late antiquity. We conclude that an admixture-drift model is particularly useful for interpreting the genetic structure and recent demographic history of small-scale populations in which social-cultural features play a significant role.
[...]
Here we focus on four more Commons from the Padana Plain in Northern Italy (Figure 1). Two of them (Nonantola and S. Agata Bolognese) are located in the Central Padana Plain (from now on Central Commons), in the same area of the previously mentioned S. Giovanni in Persiceto, with which they also share the denomination of Partecipanza. The remaining two (Grignano Polesine and Massenzatica) are at the Easternmost fringes of the Padana Plain, not far from the Po delta (from now on Eastern Commons).
[...]
On that respect, a subtle difference between Central (Nonantola, S. Agata B.) and Eastern (Grignano P., Massenzatica) Commons emerged: Central Commons harbor haplogroups/paragroups that are among the most frequent in Northern Italy, i.e. R-U152* (S. Agata B.) and R-L2 (Nonantola); instead Eastern Commons show high frequencies of more uncommon or rare haplogroups/paragroups in Italy such as R-L51* and T-M70 (Boattini et al., 2013). All these cases can be explained based on the effects of genetic drift, according to which the frequency of some haplogroups may have increased (or decreased) by random fluctuations.
[...]
In addition, the case of the Partecipanza of S. Giovanni in Persiceto—where similar patterns where observed, most notably the higher-than-expected frequency of the otherwise rare haplogroup I1-L22—suggested that external admixture could have played a significant role in the genetic history of Commons.
Stefania Sarno, Rajiv Boscolo Agostini, Sara De Fanti, Gianmarco Ferri, Silvia Ghirotto, Giorgia Modenini, Davide Pettener, Alessio Boattini
First published: 10 May 2021 https://doi.org/10.1002/ajpa.24302
Abstract
Objectives
Genetic drift and admixture are driving forces in human evolution, but their concerted impact to population evolution in historical times and at a micro-geographic scale is poorly assessed. In this study we test a demographic model encompassing both admixture and drift to the case of social-cultural isolates such as the so-called “Commons.”
Materials and methods
Commons are peculiar institutions of medieval origins whose key feature is the tight relationship between population and territory, mediated by the collective property of shared resources. Here, we analyze the Y-chromosomal genetic structure of four Commons (for a total of 366 samples) from the Central and Eastern Padana plain in Northern Italy.
Results
Our results reveal that all these groups exhibit patterns of significant diversity reduction, peripheral/outlier position within the Italian/European genetic space and high frequency of Common-specific haplogroups. By explicitly testing different drift-admixture models, we show that a drift-only model is more probable for Central Padana Commons, while additional admixture (~20%) from external population around the same time of their foundation cannot be excluded for the Eastern ones.
Discussion
Building on these results, we suggest central Middle Ages as the most probable age of foundation for three of the considered Commons, the remaining one pointing to late antiquity. We conclude that an admixture-drift model is particularly useful for interpreting the genetic structure and recent demographic history of small-scale populations in which social-cultural features play a significant role.
[...]
Here we focus on four more Commons from the Padana Plain in Northern Italy (Figure 1). Two of them (Nonantola and S. Agata Bolognese) are located in the Central Padana Plain (from now on Central Commons), in the same area of the previously mentioned S. Giovanni in Persiceto, with which they also share the denomination of Partecipanza. The remaining two (Grignano Polesine and Massenzatica) are at the Easternmost fringes of the Padana Plain, not far from the Po delta (from now on Eastern Commons).
[...]
On that respect, a subtle difference between Central (Nonantola, S. Agata B.) and Eastern (Grignano P., Massenzatica) Commons emerged: Central Commons harbor haplogroups/paragroups that are among the most frequent in Northern Italy, i.e. R-U152* (S. Agata B.) and R-L2 (Nonantola); instead Eastern Commons show high frequencies of more uncommon or rare haplogroups/paragroups in Italy such as R-L51* and T-M70 (Boattini et al., 2013). All these cases can be explained based on the effects of genetic drift, according to which the frequency of some haplogroups may have increased (or decreased) by random fluctuations.
[...]
In addition, the case of the Partecipanza of S. Giovanni in Persiceto—where similar patterns where observed, most notably the higher-than-expected frequency of the otherwise rare haplogroup I1-L22—suggested that external admixture could have played a significant role in the genetic history of Commons.
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