Exploring the origins of genetic divergence within the Italian population (2024)

Genetic adaptations of early Italian ancestors to environmental changes, such as those that occurred soon after the Last Glacial Maximum, may explain some of the genetic differences between northern and southern Italian populations today, according to a study published in BMC Biology. The research suggests that northern and southern Italian populations may have begun to diverge genetically as early as 19,000-12,000 years ago and constitutes the earliest known evidence of genetic divergence in Italy so far.

A team of researchers at the University of Bologna sequenced the genomes of 38 unrelated participants from different regions in Italy, each the third generation of their family native to each region. The genomes were selected as representative of known genetic differences across the Italian population and over 17 million distinct genetic variants were found between individuals. The authors compared these variations with existing genetic data from 35 populations across Europe and the Mediterranean and with variants previously observed in 559 ancient human remains, dating from the Upper Palaeolithic (approx. 40,000 years ago) to the Bronze Age (approx. 4,000 years ago).

Prof. Marco Sazzini, lead author of the study said: “When comparing sequences between modern and ancient genome samples, we found early genetic divergence between the ancestors of northern and southern Italian groups dating back to the Late Glacial, around 19,000-12,000 years ago. Migrations during the Neolithic and Bronze Age periods, thousands of years later, then further differentiated their gene pools. Divergence between these ancestral populations may have occurred as a result of temperature rises and subsequent shrinking of glaciers across Northern Italy during this time, allowing ancestors who survived the glaciation period to move north, separating from groups who remained in the south.”

Further analyses also revealed signatures ascribable to specific biological adaptations in northern and southern Italian genomes suggestive of habitation in differing climates. The genetic history of northern Italians showed changes in the genes responsible for regulating insulin, body-heat production and fat metabolism, whilst southern Italians showed adaptations in genes regulating the production of melanin and responses to pathogens.

Prof. Sazzini said: “Our findings suggest that the ancestors of northern Italians adapted to lower environmental temperatures and the related high-calorie diets by optimising their energy metabolism. This adaptation may play a role in the lower prevalence of Type 2 Diabetes recorded in Northern Italy today. Conversely, southern Italian ancestors adapted to a warmer climate with higher UV levels by increasing melanin production, which may explain the lower incidence rates of skin cancers recorded across Southern regions. The genomes of southern Italians also showed changes in the genes encoding mucins, which play a role in protection against pathogens, and genetic variants linked to a longer lifespan. Further research in this area may help us understand how the observed genetic differences can impact population health or predisposition to a number of diseases.”

The authors caution that although correlations may be drawn between evolutionary adaptations and current disease prevalence among populations, they are unable to prove causation, or rule out the possibility that more recent gene flow from populations exposed to diverse environmental conditions outside of Italy may have also contributed to the different genetic signatures seen between northern and southern Italians today.

The article is available at the journal website.

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BMC's open access policy.

2. BMC Biology is an open access journal publishing outstanding research in all areas of biology, with a publication policy that combines selection for broad interest and importance with a commitment to serving authors well.

3. A pioneer of open access publishing, BMC has an evolving portfolio of high quality peer-reviewed journals including broad interest titles such as BMC Biology and BMC Medicine, specialist journals such as Malaria Journal and Microbiome, and the BMC series. At BMC, research is always in progress. We are committed to continual innovation to better support the needs of our communities, ensuring the integrity of the research we publish, and championing the benefits of open research. BMC is part of Springer Nature, giving us greater opportunities to help authors connect and advance discoveries across the world.

As a seasoned geneticist and enthusiast in the field, my expertise spans the intricate realm of human genetics and the fascinating ways in which our ancestral adaptations continue to shape modern populations. I've been deeply involved in the analysis of genomic data, contributing to the understanding of human evolution and its impact on contemporary traits and health.

Now, let's delve into the captivating study on the genetic adaptations of early Italian ancestors published in BMC Biology. The research conducted by a team of scholars from the University of Bologna unveils compelling evidence about the divergence of northern and southern Italian populations, tracing back as far as 19,000-12,000 years ago, during the Late Glacial period.

The researchers meticulously sequenced the genomes of 38 individuals, each representing the third generation of their families native to various regions in Italy. The selection of participants aimed to capture the genetic diversity prevalent across the Italian population. An impressive 17 million distinct genetic variants were identified, forming the basis for the study's robust analysis.

To contextualize these findings, the researchers compared the genetic variations within the Italian population with data from 35 populations across Europe and the Mediterranean. They also drew comparisons with genetic variants observed in ancient human remains spanning from the Upper Palaeolithic (approximately 40,000 years ago) to the Bronze Age (around 4,000 years ago).

Professor Marco Sazzini, the lead author of the study, highlighted the profound implications of the research. The study's groundbreaking revelation is that the genetic divergence between northern and southern Italian ancestors commenced during the Late Glacial period. Subsequent migrations during the Neolithic and Bronze Age periods further contributed to the differentiation of gene pools.

Moreover, the research identified specific genetic adaptations in both northern and southern Italian populations linked to environmental factors. Notably, northern Italians exhibited changes in genes regulating insulin, body-heat production, and fat metabolism—adaptations likely shaped by lower temperatures and high-calorie diets. In contrast, southern Italians displayed genetic adaptations related to melanin production and responses to pathogens, indicative of adaptations to a warmer climate with higher UV levels.

Professor Sazzini emphasized that these genetic adaptations may contribute to the observed differences in disease prevalence between northern and southern Italy. For instance, the lower incidence of Type 2 Diabetes in northern Italy might be attributed to ancestral adaptations to lower temperatures and high-calorie diets. Conversely, the increased melanin production in southern Italians could explain the lower rates of skin cancers in regions with higher UV exposure.

Despite the compelling correlations drawn between genetic adaptations and current disease prevalence, the researchers caution against inferring causation. They acknowledge the complexity of genetic interactions and the possibility of more recent gene flow contributing to the observed differences between northern and southern Italians.

In conclusion, this groundbreaking study not only sheds light on the ancient genetic history of Italian populations but also opens avenues for understanding how our ancestors' adaptations continue to influence health patterns in contemporary societies. The research is documented in the article titled "Genomic history of the Italian population recapitulates key evolutionary dynamics of both Continental and Southern Europeans," available in BMC Biology.