Genetic history of Italy

The genetic history of Italy is greatly influenced by geography and history. The ancestors of Italians are mostly Indo-European speakers (e.g. Italic peoples such as the Latins, Umbrians, Samnites, Oscans, Sicels and Adriatic Veneti, as well as Celts in the north and Iapygians and Greeks in the south) and pre-Indo-European speakers (the Etruscans and Rhaetians in mainland Italy, Sicani and Elymians in Sicily and the Nuragic people in Sardinia). During the imperial period of Ancient Rome, the city of Rome was also home to several peoples with origins from diverse regions in the Mediterranean basin, such as Southern Europe, North Africa and the Middle East, in search of better opportunities or as slaves, but who did not leave a significant or lasting genetic legacy in the subsequent centuries after Rome's decline and fall.
Based on DNA analysis, there is evidence of ancient regional genetic substructure and continuity within modern Italy dating to the pre-Roman and early Roman periods. DNA analysis also demonstrates that ancient Greek colonization had a significant lasting effect on the local genetic landscape of Southern Italy and Sicily ("Magna Graecia"), with modern people from that region having significant Greek admixture. Latin samples from Latium in the Iron Age and early Roman Republican period, were generally found to genetically cluster closest to modern Northern and Central Italians (four out of six were closest to Northern and Central Italians, while the other two were closest to Southern Italians). Overall, the genetic differentiation between the Latins, Etruscans and the preceding proto-Villanovan population of Italy was found to be insignificant. In 2019, aDNA analysis of Roman fossils detected some genetic contribution of Northern European ancestry to the medieval inhabitants of the city of Rome, from donor sources possibly related to the Lombards, and Visigoths. A 2020 analysis of maternal haplogroups from ancient and modern samples indicates a substantial genetic similarity and continuity between the modern inhabitants of Umbria in central Italy and ancient inhabitants of the region belonging to the Italic-speaking Umbrian culture. 
Multiple DNA studies confirmed that genetic variation in Italy is clinal, going from the Eastern to the Western Mediterranean, with the Sardinians being the exception as genetic outliers in Italy and Europe that results from their predominantly Neolithic, Pre-Indo-European and non-Italic Nuragic ancestry. Reflecting the history of Europe and the broader Mediterranean basin, the Italian populations have been found to be made up mostly of the same ancestral components, albeit in different proportions, related to the Mesolithic, Neolithic and Bronze Age settlements of Europe. In their admixture ratios, the Italians are similar to other Southern Europeans, and that is being of primarily Neolithic Early European Farmer ancestry, along with smaller, but still significant, amounts of Mesolithic Western Hunter-Gatherer, Bronze Age Steppe pastoralist (Indo-European speakers) and Chalcolithic or Bronze Age Iranian/Caucasus-related ancestry. Sicilians and Southern Italians are closest to the Greeks (as the historical region of "Magna Graecia", "Great Greece", bears witness to), while the Northern Italians are closest to the Spaniards and southern French. There is also minor Bronze/Iron Age Middle Eastern and North African admixture in southern Italy and Sardinia, with the highest incidence being in Sicily.
The genetic gap between the northern and southern Italians is filled by an intermediate Central Italian cluster, creating a continuous cline of variation that mirrors geography. The genetic distance between the Northern and the Southern Italians, although pretty large for a single European nationality, is only roughly equal to the one between the Northern and the Southern Germans. A study on some linguistic and isolated communities residing in Italy revealed that their genetic diversity is greater than that observed throughout the entire European continent at short (0–200 Km) and intermediate distances (700–800 Km), and account for most of the highest values of genetic distances observed at all geographic ranges. Indeed, Northern and Southern Italians began to diverge as early as the Late Glacial and thus appear to encapsulate at a micro-geographic scale the cline of genetic diversity observable across Europe. The only exceptions are some minority populations (mostly Slovene minorities from the region of Friuli-Venezia Giulia) who cluster with the Slavic-speaking Central Europeans from Slovenia, as well as the Sardinians, who appear to be clearly differentiated from the populations of both mainland Italy and Sicily.
Historical populations of Italy.
Modern humans appeared during the Upper Paleolithic. Specimens of Aurignacian age were discovered in the cave of Fumane and dated back about 34,000 years ago. During the Magdalenian period the first humans from the Pyrenees populated Sardinia.
During the Neolithic farming was introduced by people from the east and the first villages were built, weapons became more sophisticated and the first objects in clay were produced. In the late Neolithic era the use of copper spread and villages were built over piles near lakes. In Sardinia, Sicily and part of Mainland Italy the Beaker culture spread from Western and Central Europe.
During the Late Bronze Age the Urnfield Proto-Villanovan culture appeared in Central and Northern Italy, characterized by the typical rite of cremation of dead bodies originating from Central Europe, and the use of iron spread. In Sardinia, the Nuragic civilization flourished.
At the dawn of the Iron Age much of Italy was inhabited by Italic tribes such as the Latins, Sabines, Samnites, Umbrians; the Northwest and Alpine territories were populated primarily by pre-Indo European speakers like the Etruscans, Ligurians, Camunni and Raetians; while Iapygian tribes, possibly of Illyrian origin, populated Apulia.
From the 8th century BC, Greek colonists settled on the southern Italian coast and founded cities, initiating what would be later called Magna Graecia. Around the same time, Phoenician colonists settled mainly on the western side of Sicily. During the same period Etruscan civilization developed on the coast of Southern Tuscany and Northern Latium. In the 4th century BC Gauls settled in Northern Italy and parts of Central Italy. With the fall of the Western Roman Empire, different populations of Germanic origin invaded Italy, the most significant being the Lombards, followed five centuries later by the Normans in Sicily.
Y-DNA genetic diversity.
Many Italians, especially in Northern Italy and Central Italy, belong to Haplogroup R1b, common in Western and Central Europe. The highest frequency of R1b is found in Garfagnana (76.2%) in Tuscany and in the Bergamo Valleys (80.8%) in Lombardy, Northern regions. This percentage lowers in the south of Italy in Calabria (26.5%). On the other hand, the majority of the Sardinians belong to Mesolithic European haplogroup I2a1a.
A study from the Università Cattolica del Sacro Cuore found that while Greek colonization left little significant genetic contribution, data analysis sampling 12 sites in the Italian peninsula supported a male demic diffusion model and Neolithic admixture with Mesolithic inhabitants. The results supported a distribution of genetic variation along a north–south axis and supported demic diffusion. South Italian samples clustered with southeast and south-central European samples, and northern groups with West Europe..>
A 2004 study by Semino et al. showed that Italians from the north-central regions had around 26.9% J2; the Apulians, Calabrians and Sicilians had 31.4%, 24.6% and 23.8% J2 respectively; the Sardinians had 12.5% J2.
A 2018 genetic study, focusing on the Y-chromosome and haplogroups lineages, their diversity and their distribution by taking some 817 representative subjects, gives credit to the traditional northern-southern division in population, by concluding that due to Neolithic migrations southern Italians "show a higher similarity with Middle Eastern and Southern Balkan populations than northern ones; conversely, northern samples are genetically closer to North-West Europe and Northern Balkan groups". The intermediate position of Volterra in central Tuscany is a mark of its unique Y-chromosomal genetic structure. It also keeps the debate about the origins of Etruscans open: the presence of J2a-M67* could substantiate the hypothesis of Herodotus, of a migration from the sea of a population related to the Anatolians; the presence of Central European lineage G2a-L497 at considerable frequency would rather support a Central European origin of the Etruscans; and finally, the high incidence of European R1b lineages—especially of haplogroup R1b-U152—could suggest an autochthonous origin due to a process of formation of the Etruscan civilisation from the preceding Villanovan culture, following the theories of Dionysius of Halicarnassus.
Y-DNA introduced by historical immigration.
In two villages in Lazio and Abruzzo (Cappadocia and Vallepietra), I1 is the most common Y-DNA, recorded at levels 35% and 28%. In Sicily, further migrations from the Vandals and Saracens have only slightly affected the ethnic composition of the Sicilian people. However, Greek genetic legacy is estimated at 37% in Sicily.
The Norman Kingdom of Sicily was created in 1130, with Palermo as capital, 70 years after the initial Norman invasion and 40 after the conquest of the last town, Noto in 1091, and would last until 1198. Nowadays it is in north-west Sicily, around Palermo and Trapani, that Norman Y-DNA is common, with 15% to 20% of the lineages belonging to haplogroup I. The North African male contribution to Sicily was estimated between 3.5% and 7.5%. Overall the estimated Central Balkan and North Western European paternal contributions in South Italy and Sicily are about 63% and 26% respectively.
A 2015 genetic study of six small mountain villages in eastern Lazio and one mountain community in nearby western Abruzzo found some genetic similarities between these communities and Near Eastern populations, mainly in the male genetic pool. The Y haplogroup Q, common in Western Asia and Central Asia, was also found among this sample population, suggesting that in the past could have hosted a settlement from Central Asia.
Genetic composition of Italian mtDNA.
In Italy as elsewhere in Europe the majority of mtDNA lineages belong to the haplogroup H. Several independent studies conclude that haplogroup H probably evolved in West Asia c. 25,000 years ago. It was carried to Europe by migrations c. 20–25,000 years ago, and spread with population of the southwest of the continent. Its arrival was roughly contemporary with the rise of the Gravettian culture. The spread of subclades H1, H3 and the sister haplogroup V reflect a second intra-European expansion from the Franco-Cantabrian region after the last glacial maximum, c. 13,000 years ago.
African Haplogroup L lineages are relatively infrequent (less than 1%) throughout Italy with the exception of Latium, Volterra, Basilicata and Sicily where frequencies between 2 and 3% have been found.
A study in 2012 by Brisighelli "et al." stated that an analysis of ancestral informative markers "as carried out in the present study indicated that Italy shows a very minor sub-Saharan African component that is, however, slightly higher than non-Mediterranean Europe." Discussing African mtDNAs the study states that these indicate that a significant proportion of these lineages could have arrived in Italy more than 10,000 years ago; therefore, their presence in Italy does not necessarily date to the time of the Roman Empire, the Atlantic slave trade or to modern migration." These mtDNAs by Brisighelli "et al." were reported with the given results as "Mitochondrial DNA haplotypes of African origin are mainly represented by haplogroups M1 (0.3%), U6 (0.8%) and L (1.2%)" for the 583 samples tested. The haplogroups M1 and U6 can be considered to be of North African origin and could therefore be used to signal the documented African historical input. Haplogroup M1 was observed in only two carriers from Trapani (West Sicily), while U6 was observed only in Lucera, South Apulia, and another at the tip of the Peninsula (Calabria).
A 2013 study by Alessio Boattini et al. found 0 of African L haplogroup in the whole Italy out of 865 samples. The percentages for Berber M1 and U6 haplogroups were 0.46% and 0.35% respectively.
A 2014 study by Stefania Sarno et al. found 0 of African L and M1 haplogroups in mainland Southern Italy out of 115 samples. Only two Berber U6 out of 115 samples were found, one from Lecce and one from Cosenza.
A close genetic similarity between Ashkenazim and Italians has been noted in genetic studies, possibly due to the fact that Ashkenazi Jews have a significant European admixture (30–60%), much of it Southern European, a lot of which came from Italy when Jewish diaspora males of Middle Eastern origin migrated to Rome and found wives among local women who then converted to Judaism. More specifically, Ashkenazi Jews could be modeled as being 50% Levantine and 50% European, with an estimated mean South European admixture of 37.5%. Most of it (30.5%) seems to derive from an Italian source.
A 2010 study of Jewish genealogy found that with respect to non-Jewish European groups, the populations which are most closely related to Ashkenazi Jews are modern-day Italians followed by the French and Sardinians.
Recent studies have shown that Italy played an important role in the recovery of "Western Europe" at the end of the Last glacial period. The study which was focused on the mitochondrial U5b3 haplogroup discovered that this female lineage had in fact originated in Italy and around 10,000 years ago it expanded from the Peninsula towards Provence and the Balkans. In Provence, probably between 9,000 and 7,000 years ago, it gave rise to the haplogroup subclade U5b3a1. This subclade U5b3a1 later came from Provence to the island of Sardinia by way of obsidian merchants, because it is estimated that 80% of the obsidian which is found in France comes from Monte Arci in Sardinia, reflecting the close relationship which once existed between these two regions. Still about 4% of the female population of Sardinia belongs to this haplotype.
A 2020 analysis of maternal haplogroups from ancient and modern samples in the central Italian region of Umbria finds a substantial genetic similarity among modern Umbrians and the area's pre-Roman inhabitants, and evidence of substantial genetic continuity in the region from pre-Roman times to the present. Both modern and ancient Umbrians were found to have high rates of mtDNA haplogroups U4 and U5a, and an overrepresentation of J (at roughly 30%). The study also found that, "local genetic continuities are further attested to by six terminal branches (H1e1, J1c3, J2b1, U2e2a, U8b1b1 and K1a4a)" also shared by ancient and modern Umbrians.
Autosomal.
By using the ADMIXTURE software, the authors obtained at K = 4 the lowest cross-validation error. The HapMap CEU individuals showed an average Northern Europe (NE) ancestry of 83%. A similar pattern is observed in French, Northern Italian and Central Italian populations with a NE ancestry of 70%, 56% and 52% respectively. According to the PCA plot, also in the ADMIXTURE analysis there are relatively small differences in ancestry between Northern Italians and Central Italians while Southern Italians showed a lower average admixture NE proportion (44%) than Northern and Central Italy, and a higher Caucasian ancestry of 28%. The Sardinian samples display a pattern of crimson common to the others European populations but at a higher frequency (70%).
The average admixture proportions for Northern European ancestry within current Sardinian population is 14.3% with some individuals exhibiting very low Northern European ancestry (less than 5% in 36 individuals on 268 accounting the 13% of the sample).