Finding agriculture's 'genetic signature'

The hunter gatherers were to change their ways

Modern Europeans can trace a great deal of their ancestry to Middle or Near Eastern farmers who moved into the continent 10,000 years ago.

The assessment comes from a new computer and genetics study which has sought to understand how the new agrarian technologies were introduced to the region.

It is clear from the work that it was not purely a spread of ideas - but a mass movement of people who settled and mixed with the hunter gatherers who dominated Europe at that time.

The new study is published in the journal Proceedings of the National Academy of Sciences.

Genetic 'signature'

Anthropologists believe agriculture probably started in the Middle East and then swept into Europe about 8,000 BC.

The debate has centred on whether the lifestyle changes at that time represented simply an "invasion" of ideas and practices or were led by a large immigrant population who mixed with the native people.

If the latter is correct, there should be a genetic "signature" left in the modern gene pool.

Lounes Chikhi, from University College London (UCL), UK, and colleagues looked for this marker by analysing mutations (errors) on Y chromosomes, the bundles of DNA handed down from father to son.

Computer analysis

In particular, they studied rare mutations called unique event polymorphisms (UEPs). These are not thought to have occurred more than once in recent human history.

The presence of UEPs in different populations is likely to indicate common ancestry rather than recurrent changes in gene structure.

The research team took the results of a previous study and subjected them to a new computer-intensive technique. From this, the scientists estimate that Middle Eastern farmers contributed about 50% of the analysed genes to the modern European population.

Contributions ranged from 15-30% in France and Germany, to 85-100% in southeastern European countries such as Albania, Macedonia, and Greece.

These figures are much larger than previous ones, suggesting that the Middle Eastern contribution to European genetic heritage has been underestimated.

Small and large

"Archaeologists have shown that farming moved from the Near East to North West Europe... but we've never known how it happened," Dr Chikhi told the BBC.

"We know that farming spread across Europe at approximately one kilometre a year - or 20 km per generation."

The UCL researcher added: "All Europeans have hunter-gatherer genes, but they also have Near East farmers' genes.

"There are clear differences between regions in Europe. For instance, in Greece and the Balkans an individual has between 70-100% of genes from Near East farmers, but in western France and England as little as 10% of an individual's genes can come from the Near East."