DNA from ancient skeletons has revealed how a complex patchwork of prehistoric migrations fashioned the modern European gene pool.
The study appears to refute the picture of Europeans as a simple mixture of indigenous hunters and Near Eastern farmers who arrived 7,000 years ago.
The findings by an international team have been published in Science journal.
DNA was analysed from 364 skeletons unearthed in Germany - an important crossroads for prehistoric cultures.
"This is the largest and most detailed genetic time series of Europe yet created, allowing us to establish a complete genetic chronology," said co-author Dr Wolfgang Haak of the Australian Centre for DNA (ACAD) in Adelaide.
"Focusing on this small but highly important geographic region meant we could generate a gapless record, and directly observe genetic changes in 'real-time' from 7,500 to 3,500 years ago, from the earliest farmers to the early Bronze Age."
Dr Haak and his colleagues analysed DNA extracted from the teeth and bones of well-preserved remains from the Mittelelbe-Saale region of Germany. They focused on mitochondrial DNA (mtDNA) - the genetic information in the cell's "batteries".
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When you look at today's populations, what you are seeing is a hazy palimpsest of what actually went on to create present-day patterns”
Dr Spencer Wells Director, Genographic Project
MtDNA is passed down from a mother to her children, allowing geneticists to probe the maternal histories of populations. Geneticists recognise a variety of mitochondrial DNA "clans", or lineages, in human populations. And each of these lineages has its own distinct history.
The team's results show that indigenous hunter-gatherers in Central Europe were edged out by incomers from Anatolia (modern Turkey) some 7,500 years ago. A majority of the hunters belonged to the maternal clan known as haplogroup U, whilst the farmers carried a selection of genetic lineages characteristic of the Near East.
Around 6,100 years ago, farming was introduced to Scandinavia, which coincided with the appearance of Neolithic mtDNA lineages in that region too.
"In some ways agriculture was an obvious and easy way to go in the Fertile Crescent. But once you take it out of there, it involves an abrupt shift in lifestyle," said Dr Spencer Wells, director of the Genographic Project and an Explorer-in-Residence at National Geographic, adding that early agricultural groups were living "on the edge".
"They were basically taking crops that had evolved over millions of years in the Middle East and were adapted to that dry-wet pattern of seasonality and moving them into an area that was recently de-glaciated.
More at http://www.bbc.co.uk/news/science-environment-24475342