A collaborative research effort between the University of Adelaide and Harvard Medical School in Boston has yielded a Eureka moment in revealing the spread of the Indo-European mother language through Europe.
Historical linguists have long known that hundreds of languages ranging from English, Spanish, Russian and Hindi fall on the same family tree, but the reasons why have been a source of contention.
Dr Wolfgang Haak, from the University of Adelaide's Australian Centre for Ancient DNA (ACAD), is co-first author of the study published today in the journal Nature.
He said that at least some of the Indo-European languages spoken in Europe were likely the result of a massive migration from eastern Russia around 4500 years ago.
This large migration almost certainly had lasting effects on the languages people spoke.
"This new study is the biggest of its kind so far and has helped to improve our understanding of the linguistic impact of Stone Age migration," Dr Haak said.
The team from ACAD used genome-scale data from more than 90 ancient skeletons found around Europe, ranging from 3000 to 8000 years old. Using the data, the Australian Centre for Ancient DNA was able to trace their origins in partnership with Harvard Medical School.
"These results challenge the other popular theory that all Indo-European languages in Europe today owe their origin to the arrival of the first farmers from Anatolia more than 8000 years ago," said the leader of the study, Professor David Reich of Harvard Medical School.
Evidence pointed to two major population replacements in Europe during the Stone Age. The first was the arrival of Europe's first farmers, who spread from Anatolia, an area encompassing much of modern-day Turkey.
"Their genetic profiles show remarkable similarity despite vast geographic distances and differences in material culture. Whether from Hungary, Germany or Spain, the first farmers are genetically almost identical and must have come from the same origin," says ACAD Director Professor Alan Cooper, co-author on the study.
There was a resurgence in hunter-gatherer ancestry, which spread back through the agricultural populations of Europe around 5000 to 6000 years ago.
The second major turnover, and most surprising, involves a third ancestry component. Originating from the east, this DNA appears in every Central European sample after 4500 years ago.
"We had a bit of an inkling from the mitochondrial studies we did two years ago that were published in Science," says Dr Haak, "but that was only based in mitochondrial data, maternal lineages only, so it's only one side of the story."
"Now when we read the whole story, with additional samples from other geographic locations, with much better resolution using specifically selected SNP markers [an SNP, pronounced 'snip', is a DNA sequence variation commonly occurring in a population], we saw this later input was much, much bigger than we expected, which definitely lends weight to that secondary, more recent migration out of the Russian Steppe."
The data lines up well with linguistic research that suggested a more recent spread of Indo-European.
"That's enough to tell us that there's definitely a directionality going from east to west and we know where it's coming from. This large migration almost certainly had lasting effects on the languages people spoke," Dr Haak said.
This data lines up well with linguistic research that suggested a more recent spread of Indo-European, due to common words for wheeled-vehicles only being in use since around 5000 years ago.
"The Corded Ware Culture also have links in their material culture, so similarities in pots and everyday items that link them to cultures further in the east."
The next step of their research will be filling the gaps in migration routes around Europe, as well as further east where Indo-European languages are spoken.
"Particularly if we want to nail this hypothesis and put a geographical homeland somewhere in the steppes in Ukraine or Southern Russia, then we would assume that whatever was brought by these people would also be found in other populations that today speak an Indo-European language," Dr Haak said.
"That is equally likely for people further in the East, if you go to Iran or India. Currently we've only focused on Europe, but that equally applies to those regions as well. Now we have to look at both ancient and modern day Indian populations."
ACAD prepared the majority of the ancient skeletons for the study, building genomic libraries that were then enriched from a particular set of SNPs. Harvard Medical School took the data and analysed the results.
Finding useable DNA data from skeletons can be a challenge, though conditions vary - a well preserved 30,000 year old individual can hold useable information, while a poorly preserved 2,000 year old skeleton can be fairly useless for the purpose of DNA samples.
"It's okay in temperate climates such as Europe and Russia for example. It gets rarer, the further south you go, where the preservation is not very favourable. If you go to sub-tropical and tropical, the turnover of any biological material is a couple of weeks," Dr Haak said.
"Certainly with the advent of farming, we have way more permanent settlements and they come with accompanying graveyards and burial sites. They're much easier to spot than the open field camps that hunter-gatherers and foragers had. There's a bias in the amount of material, but by and large there's a substantial number of dead people around."