How Mixed Ancestries Shaped European Traits
An eye-opening new study appearing in the journal Current Biology delves into the extensive interactions between different ethnic groups that shaped the genomes of contemporary Europeans. The migrations of outside groups into Europe several thousand years ago made a decisive difference, and it was genetic mixing between migrants and previously established hunter-gatherer groups that ultimately created the people of the continent as they are seen today.
A team of genetic researchers from Italy and Estonia conducted this study, which examined thousands of genetic samples collected from currently living Europeans, specifically those who live in the country of Estonia. They were seeking more detailed information about the groups that contributed DNA to the modern individual, and what they uncovered was an incredibly complex history that left little doubt about how profoundly ancient migrations have impacted present reality.
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Modern Europeans as Living Time Capsules
The genetic makeup of modern Europeans is a mixture of three distinct groups. These include Neolithic period farmers from Anatolia (modern-day Turkey), pastoralist nomads from the grasslands of the Pontic Steppe (modern-day southern Russia plus adjacent lands to the south and west), and the hunter-gatherers these two groups encountered when they arrived on European soil. The migrations of first two groups took place within the last 10,000 years, and relations between the three groups were apparently peaceful enough in many locations to encourage interbreeding.
Several earlier studies also analyzed the various ingredients that comprise the modern European gene pool. Scientists involved in these research projects generally sought to learn more about the ancient groups, using contemporary genetic samples as a launching point to travel back in time.
But this new research project did the opposite.
"With our study, instead, we asked how the physiology and appearance of contemporary Europeans are influenced by these ancient footprints that are still embedded in their genomes," study lead author Dr. Davide Marnetto, a geneticist from the University of Tartu (Estonia), explained in an Estonian Research Council report .
The three ancient populations that form the contemporary European gene pool, with the addition of Siberian (peculiar to the Estonian genomes analyzed in this study) are represented here along with the inferred contribution (increase, decrease or nothing) they made to a number of body and health traits in present day individuals. For eye and hair color, symbols point to the shade most likely contributed by a given ancestry. (Davide Marnetto / Current Biology )
Some of the contemporary characteristics that were analyzed included hair and eye color, height, weight, heart rates, and cholesterol levels. It is possible for researchers to identify areas within the genome that control the development of such traits, and link them to genetic inputs provided long ago by one group or another.
"As a case study, we used the Estonian population, which also displays some genetic components frequent in present-day Siberian populations, because of the rich data provided by the Estonian Biobank, where we could find the genome and trait characterization for more than 50,000 samples,” Dr. Marnetto said. “We specifically measured whether having a certain feature … is coupled with having inherited more variants from a specific ancestry.”
Testifying to the success of their project, the Italian and Estonian researchers were able to link many distinct characteristics to ancient populations.
From the hunter-gatherer populations that existed before the migrants arrived, Europeans inherited blue eyes, lower cholesterol levels, a higher Body Mass Index (BMI), and darker hair colors. Anatolian farmers added blond hair to the mix, along with lower heart rates and a tendency to have a lower BMI. Steppe pastoralists contributed a tendency for higher cholesterol, along with the greater height and sturdier build of modern Europeans in general in comparison to earlier occupants of the region.
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Europeans inherited blue eyes, lower cholesterol levels, a higher Body Mass Index (BMI), and darker hair colors from pre-migration hunter-gatherers. ( endrews21/ Adobe Stock)
All Europeans possess DNA passed down from each of the three groups. The mixtures are obviously quite different from family to family and from individual to individual, but in general the roots of many traits present can be found several thousand years in the past.
The Anatolian and Pontic Steppe Migrations and their Impact
Hunter-gatherer populations occupied much of Europe during the early part of the Neolithic period (the Neolithic as a whole lasted from approximately 15,000 BC to 3,000 BC). Farmers from the Near East (Anatolia) began to migrate into the region during the middle Neolithic, and once they did, they began to interbreed with the local populations almost immediately.
In 2017, a team of international researchers published an article in the journal Nature that revealed how Anatolian DNA eventually became dominant among Neolithic populations in the areas of what are now Germany, Spain, and Hungary. Ancient genetic samples taken from people in these regions who lived between the years 6,000 and 2,200 BC found only remnants of the original hunter-gatherer peoples, showing that interbreeding between the Near East agriculturalists and the local population had been extensive.
As for the Pontic steppe nomads, they arrived as invaders into central Europe approximately 4,500 years ago, during the early Bronze Age . This wave of migrants belonged to the Yamnaya culture , which came from Russian and Ukrainian grasslands north of the Black Sea . These pastoralists arrived in large numbers, and their DNA soon eclipsed that of the indigenous residents with whom they interacted. Up to 75 percent of the DNA detected in central European populations from 4,500 years ago has been revealed to have come from Pontic steppe nomads , which show how widespread interbreeding between the two groups actually was.
Representation of a Yamnaya Culture horse rider. The peoples came to Europe from modern-day western Russia or the Ukraine. ( katiekk2 / Adobe stock)
In addition to their genetic contributions, the steppe nomads also introduced domestic horses and the wheel to Europe. Their arrival represented a significant moment in European history, from a cultural as well as a genetic standpoint.
The Future Advance of Migration Genetics
The researchers involved in this study focused on Europeans because of the availability of the Estonian genetic databank. Samples from other ethnicities are harder to come by, which limits the ability of scientists to do studies on those groups.
“There is absolutely no evidence indicating that Europe encompasses higher genetic diversity and more complex heritage than other continents,” Dr. Marnetto said. “An increased coverage of samples from across the world is crucial to enhance our understanding on how past human history shaped the trait variability displayed by contemporary individuals.”
This new study has likely set a template other genetic scientists will follow in the future, as they seek to learn more about how human genetic inheritance has been influenced by migration, in particular regions but also across the globe as a whole.
Top image: European traits vary due to historic genetic influences. Here a blue-eyed, blonde-haired woman, typical traits of Estonia where the study is based. Source: Jeremy Francis / Adobe Stock
By Nathan Falde