HUNDREDS of languages, from English to Hindustani, are all derived from a single ancestral tongue. Now DNA from ancient bones suggests that the people who spoke this primal language lived somewhere south of the Caucasus mountains in western Asia.
Languages evolve and diversify, much like biological species. Today, about 3 billion people speak an Indo-European language, such as English, Spanish, Hindustani and Nepali. All of these are descended from a common ancestor.
This hypothetical ancient language, Proto-Indo-European (PIE), was spoken somewhere in Eurasia between about 5500 and 9000 years ago. But linguists are unsure where.
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There are two leading ideas. According to these, the PIE homeland was either on the western Eurasian steppe somewhere north of the Caucasus mountains, or somewhere to the south of those mountains, perhaps in the Fertile Crescent in western Asia, where farming first developed.
Indo-European languages were ultimately spoken in both regions. This suggests that the ancient inhabitants of the Caucasus mountains, which lie between the two proposed homelands, might hold crucial clues.
To investigate, Wolfgang Haak at the Max Planck Institute for the Science of Human History in Jena, Germany, and his colleagues examined DNA from 45 ancient humans who lived in the Caucasus region between about 3200 and 6500 years ago.
鈥淚f DNA dispersed north via the Caucasus mountains 6500 years ago, languages may have done so too鈥�
The ancient DNA suggested that genes 鈥� and people 鈥� were flowing through the Caucasus mountains 6500 years ago. But the flow appears to have been largely one-way: from south to north.
Those living in the northern part of the mountains 6500 years ago had genes similar to those previously detected in prehistoric farmers who lived in the north-east Fertile Crescent, in western Iran. What鈥檚 more, this 鈥淚ranian farmer鈥� genetic signature also spread to the Eurasian steppe.
If DNA dispersed north via the Caucasus mountains and onto the Eurasian steppe 6500 years ago, it is possible that languages did too. The researchers conclude that the PIE homeland may have been south of the mountains (bioRxiv, ).
A PIE homeland in this region makes sense, says linguist Paul Heggarty, who also works at the Max Planck Institute for the Science of Human History, but was not involved in the paper.
He points to studies published since 2015 that suggested the prehistoric inhabitants of the Eurasian steppe had genetic links to ancient farming populations in the Fertile Crescent. 鈥淏ut it鈥檚 much clearer now that the direction of the spread is going from south to north,鈥� he says.
Yet the new study goes against the trend: in recent years, the idea that the PIE homeland was on the Eurasian steppe has been gaining ground. The argument is unlikely to be settled any time soon.
This article appeared in print under the headline 鈥淔ound: origin of ancestral language鈥�