NEW YORK (GenomeWeb) – A genomic analysis of ancient human remains from sites in Europe and Central Asia is providing a peek at the diverse populations that moved in and out of the area during the Bronze Age, between around 3,000 and 5,000 years ago.
As they reported online today in Nature, members of an international team led by investigators at the University of Copenhagen did genome sequencing on 101 ancient European individuals, focusing on remains dated to the Late Neolithic period, the Bronze Age, and early Iron Age.
The team's results suggest that present-day population patterns largely became established during the Bronze Age and support the notion that migrations by the Yamnaya population into northern and central Europe during this period contributed to the spread of Indo-European language groups.
"The results show that the genetic composition and distribution of peoples in Europe and Asia today is a surprisingly late phenomenon — only a few thousand years old," senior author Eske Willerslev, director of the University of Copenhagen's Centre for GeoGenetics, said in a statement.
Past archeological studies have found signs of pronounced cultural changes in Europe and Asia during the Bronze Age, with Stone Age, or Neolithic, farming cultures being replaced by new economic systems, social structures, tools, and weaponry in many parts of Eurasia.
Still, it's unclear whether such changes were a consequence of cultural diffusion of human migration, the study's authors noted. To explore this with genomic data, they turned to ancient tooth samples representing different points of the Bronze Age and parts of the Late Neolithic and Iron Ages.
Using DNA from the outer layer of tooth samples, combined with techniques for boosting ancient DNA extraction and minimizing contamination, the team sequenced 19 of the ancient genomes to average depths of 1.1 to 7.4-fold. The remaining samples were sequenced to less than one-fold average depth apiece.
Comparisons with present day and ancient genome sequences pointed to distinct population structures within the Europe and Central Asia during the Bronze Age, researchers reported.
While Stone Age individuals from northern and central Europe shared genetic features with hunter-gatherer and Neolithic farm groups, for example, the Bronze Age heralded an influx of genetic features that seem to coincide with Yamnaya population expansions from the steppe region neighboring the Caspian Sea and Caucasus Mountains.
The team detected varying levels of Yamnaya admixutre in different parts of Europe, peaking in what would become the Corded Ware culture and turning up at lowest levels in Hungarian individuals.
In Asia, too, the researchers saw genetic evidence of Yamnaya migration. In particular, their analysis suggests an Afanasievo population that lived near the Altai and Sayan mountain ranges at the intersection of Russia, Mongolia, China, and Kazakhstan was genetically identical to the Yamnaya.
The Afanasievo seem to have been replaced by successive migrations during the Bronze Age, they noted, first by the chariot-building, horse-breeding Sintashta population from the Ural mountains and later by populations with higher levels of East Asian ancestry.
By the end of the Bronze Age, the genetic patterns detected in various parts of Eurasia largely resembled those found in the regions today, the study's authors explained, hinting that "much of the basis of the Eurasian genetic landscape of today was formed during the complex patterns of expansions, admixture, and replacements during this period."
Finally, a look at derived allele frequency patterns in the ancient individuals indicated that alleles associated with light skin pigmentation and blue eyes were fairly common amongst Bronze Age Europeans. In contrast, the lactase persistence allele was still relatively rare, though present at slightly higher levels in those with Yamnaya ancestry.