Debate over whether Europeans are mostly descended from farmers from the east or hunter gatherers from the south has been given a new twist by a paper in PLoS Biology. Based on new genetic data, researchers led by Patricia Balaresque, of the University of Leicester, argue that male farmers came from the east, seducing the local women as they went.

They say their work shows that 80% of European Y chromosomes originally came from incoming farmers (paper should be here but the PLoS website seems to be down at the moment).

“In contrast, most maternal genetic lineages seem to descend from hunter-gatherers,” says Balaresque (press release). “To us, this suggests a reproductive advantage for farming males over indigenous hunter-gatherer males during the switch from hunting and gathering to farming – maybe, back then, it was just sexier to be a farmer.”

Agriculture in Europe began to spread from the Middle East in the Neolithic period, around 10,000 years ago. Up for debate however is whether this spread was mainly driven by movement of the farmers themselves, or the spread of the knowledge of farming through the Palaeolithic hunter-gatherers who had re-colonised Europe from Iberia, Italy and the Balkans after the pesky ice had retreated.

Balaresque and her colleagues analysed the commonest form of the Y-chromosome, carried by over 100 million modern European men. This form – Haplogroup R1b1b2 – increases in frequency from east to west. Around 12% of the male population have it in Eastern Turkey, rising to around 85% by the time you reach Ireland.

While others have argued that this shows that this chromosome – and hence the dominant population of Europe – spread from the west out towards the east Balaresque’s study points to a different explanation. As the paper notes, the area of highest frequency of Haplogroup R1b1b2 could be the underlying population least impacted by an incoming migration from far away or it could be the “final destination” of mass migration into a sparsely populated region.

To work out which of these two possibilities is more likely, the researchers looked at the diversity of this lineage.

Diversity should correlate with population age so if these men originally came out of the southern areas, where hunter-gatherers were sheltering from the ice, diversity should correlate with latitude. Equally, if they came out of what is now Turkey then diversity should correlate with longitude.

The team found a correlation with longitude but not with latitude.

“Taken with evidence on the origins of other lineages, this indicates that most European Y chromosomes descend from Near Eastern farmers,” they write. “In contrast, most maternal lineages descend from hunter-gatherers, suggesting a reproductive advantage for farming males over indigenous hunter-gatherer males during the cultural transition from hunting-gathering to farming.”

For some informed critique of this work, see:

Dienekes – The paper makes an important but inconclusive contribution to the question of R1b1b2 origins. We will have to wait for more ancient DNA before this question can be settled.

Gene Expression – There’s a lot of overlap, and though it is nice that the trend fits expectations, that is, regions with more R1b1b2 diversity should be those where there’s more time depth to build up that diversity, there have been so many flip-flops in this area that people will probably question dating here. One issue to note is that it seems likely that if the model presented here is true, that R1b1b2 is newcomer from the Middle East which rapidly expanded in frequency across Western Europe, it’s going to be hard to getting the clarity you need from molecular clock based methods because the demographic processes occurred rather rapidly.