The Bronze Age was a period of major cultural changes in Europe and Central Asia. However, there is debate about whether these changes resulted from the circulation of technologies or from human migrations, potentially also facilitating the spread of languages. A multidisciplinary team of scientists led by Dr Morten Allentoft from the University of Copenhagen investigated this by using innovative methods to sequence the genomes from 101 humans who lived across Eurasia between 3000 BC and 600 CE.
Localities and cultural associations of 101 sampled ancient individuals from Europe and Central Asia. Image credit: Morten E. Allentoft et al.
“Both archaeologists and linguists have had theories about how cultures and languages have spread in our part of the world. We, geneticists, have now collaborated with them to publish an explanation based on a record amount of DNA-analyses of skeletons from the Bronze Age,” explained Dr Allentoft, who is the first author of a paper published in the journal Nature.
“The driving force in our study was to understand the big economical and social changes that happened at the beginning of the third millennium BC, spanning the Urals to Scandinavia. The old Neolithic farming cultures were replaced by a completely new perception of family, property and personhood. I and other archaeologists share the opinion that these changes came about as a result of massive migrations,” added study co-author Prof Kristian Kristiansen from the University of Gothenburg.
With this new investigation, Dr Allentoft’s team confirms that the changes came about as a result of migrations.
One of the main findings from the study is how these migrations resulted in huge changes to the European gene-pool, in particular conferring a large degree of admixture on the present populations. Genetically speaking, ancient Europeans from the time post these migrations are much more similar to modern Europeans than those prior the Bronze Age.
The re-writing of the genetic map began in the early Bronze Age, about 5,000 years ago.
From the steppes in the Caucasus, the Yamna culture migrated principally westward into North- and Central Europe, and to a lesser degree, into western Siberia.
Yamna was characterized by a new system of family and property. In northern Europe, the Yamna mixed with the Stone Age people who inhabited this region and along the way established the Corded Ware culture, which genetically speaking resembles present day Europeans living north of the Alps today.
Facial reconstruction of the skull of a Yamna man who lived in the Caspian steppe around 5,000 years ago. Image credit: Alexey Nechvaloda.
Later, about 4,000 years ago, the Sintashta culture (also known as the Sintashta-Petrovka or Sintashta-Arkaim culture) evolved in the Caucasus. The culture’s sophisticated new weapons and chariots were rapidly expanding across Europe.
The area east of the Urals and far into Central Asia was colonized around 3,800 years ago by the Andronovo culture. The new findings show that this culture had a European DNA-background.
During the last part of the Bronze Age, and at the beginning of the Iron Age, East Asian peoples arrived in Central Asia. Here it is not genetic admixture the scientists see, but rather a replacement of genes. The European genes in the area disappear.
In addition to the population movement insights, the study revealed other surprises. For example, contrary to their expectations, the scientists found that lactose tolerance rose to high frequency in Europeans, in comparison to prior belief that it evolved earlier, about 5,000 – 7,000 years ago.
“Previously the common belief was that lactose tolerance developed in the Balkans or in the Middle East in connection with the introduction of farming during the Stone Age,” said Dr Martin Sikora of the University of Copenhagen.
“But now we can see that even late in the Bronze Age the mutation that gives rise to the tolerance is rare in Europe. We think that it may have been introduced into Europe with the Yamna herders from Caucasus but that the selection that has made most Europeans lactose tolerant has happened much later.”
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Morten E. Allentoft et al. 2015. Population genomics of Bronze Age Eurasia. Nature 522, 167-172; doi: 10.1038/nature14507
