August 24, 2011

New Study Challenges Origin Of European Men


A new study challenges the theory that most European men are descended from farmers who migrated from the Near East 5,000 to 10,000 years ago.

The findings lean towards the idea that most of Europe's males come from stone-age hunters.

Archaeological evidence shows that modern humans first settled in Europe about 40,000 years ago.

These early ancestors survived an Ice Age about 20,000 years ago by retreating to relatively warm refuges in the south of the continent.

However, just a few thousand years after Europe had been resettled by these hunter-gatherers, the continent went through a cultural change.

Farmers spread westwards from the area that is now Turkey, bringing a new economy and way of life with them.

The latest study from the University of Leicester focused on the Y chromosome, which is passed down from father to son.

The chromosome carried by people today can be classified into different types to help reflect their geographical origins.

Over 100 million European men carry a type known as R-M269, so identifying when this genetic group spread out is vital to understanding the people of Europe.

The researchers found that the genetic diversity of R-M269 increases even more as one moves east, towards modern Turkey.

Once the team estimated how old R-M269 was in different populations across Europe, they discovered the age ranges were more compatible with an expansion in Neolithic times.

Another study by Oxford University researchers showed no geographical trends in the diversity of R-M269.  They suggest that some of the markers on the Y chromosomes are less reliable than others for estimating the ages of genetic lineages.

They argue that current analytical tools are unsuitable for dating expansion of R-M269.

The Oxford team, lead by Cristian Capelli and George Busby, say dates based on the analysis of conventional DNA markers may have been "systematically underestimated."

However, Capelli said his study could not answer the question of when the ubiquitous R-M269 expanded in Europe.

"At the moment it's not possible to claim anything about the age of this lineage," he told BBC News, "I would say that we are putting the ball back in the middle of the field."

Co-author Dr Jim Wilson from the University of Edinburgh explained: "Estimating a date at which an ancestral lineage originated is an interesting application of genetics, but unfortunately it is beset with difficulties."

The Oxford team's paper was published in Proceedings of the Royal Society B, while the Leicester team published their findings in 2010 in PLoS Biology.


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