The human genome: a story of a many tales
Traditionally, populations that are subject to geographical or cultural barriers to admixture with other groups are considered historical peculiarities, groups relegated to extreme environments or whose culture and practices are in the process of disappearing, rather than as an integral part of human diversity. However, a recent study published in
in the journal Scientifc Reports and conducted by an international team coordinated by Sapienza University, reveals a completely different picture: the study of isolated groups allows us to understand how environment, society and demographics have shaped the DNA of human groups.
By comparing the genome structure of different European populations, Paolo Anagnostou and Giovanni Destro Bisol have detected a variability up to sixteen times higher in isolated groups than in "open" groups, such as the Spanish, Russian or Greeks. Their DNA is witness to many different human stories.
"The genomic differences amongst the three Germanic linguistic islands of Sappada, Sauris and Timau, which populated contiguous areas of the Eastern Alps during the Middle Ages”, explains Giovanni Destro Bisol, “are truly remarkable and as heterogeneous as those of groups that are very distant in terms of history and geography, like the Basques in southern France and the inhabitants of the Orkney islands off the coast of Scotland".
The reason does not lie just in the small demographic size of these three Alpine mountain enclaves, which together do not exceed a few thousand individuals, but we must also consider the importance of their sense of identity. In fact, unlike what happens in other Alpine groups, in their marriage choices, the bonds of individuals to their communities prevailed on their common Germanic ancestry.
A different case is revealed by the Cimbri, a group of Germanic origins that settled on the Asiago Plateau in the Veneto Region between the 10th and 11the centuries, and the inhabitants of Carloforte on the Island of St. Peter near the southern coast of Sardinia. Over time, the Cimbri were to a certain extent culturally assimilated and grew more open to the linguistic and genetic influence of local populations, while the isolation of the Carloforte population was mitigated over time by intermittent relations with external populations during their migrations to the area of Pegli, in Liguria, the island of Tabarka in Tunisia and the southern confines of the Sulcis.
These are the reasons for which the two groups reveal fewer genomic isolation indicators; in fact, the structure of their genome is more similar to that of open groups, like the French or Northwester Italians, than that of other isolated communities.
These new studies, funded by National Geographic, shed an entirely new light on the dichotomy defined by geneticists between open and isolated populations. Since anthropologists abandoned the concept of race, the diversity of our DNA has vanquished all attempts to classify it rigidly and simplistically, but rather it speaks to us of many different stories that only a biological and cultural approach can re-unite into the one great story of human evolution.
Anagnostou P. et al. Overcoming the dichotomy between open and isolated populations using genomic data from a large European dataset. Scientific Reports, 7:41614. DOI: 10.1038/srep41614