Ancient Britons
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The study, published today in Nature, provides the first strong genetic evidence of the Saxon invasion, and shows how much they interbred with the locals once they got there.

"When I first made this map I nearly fell out of my chair because what came up was this incredible pattern, and I could see that it matched lots of things that I already knew about British history, says lead author Dr Stephen Leslie, a statistical geneticist at the Murdoch Childrens Research Institute

Leslie and colleagues used a sophisticated statistical technique to analyse subtle genetic differences between over 8000 individual people across the United Kingdom and Europe.

They used protocols to make sure they were only studying DNA that was local to the area, by, for example, only taking the UK samples from people whose four grandparents were all born in the same rural area.

The researchers then clustered individuals into colour-coded groups, based only on their genetics, and were amazed to find that when they plotted the results on a map, the clusters corresponded to specific areas of the UK. The clustering showed northern and southern English people were genetically distinct, and in some cases clusters very accurately reflected geographical borders.

"For example you could see Cornwall was separate from Devon and that that separation was almost perfectly along the county boundary," says Leslie.

While past studies of this type have been able to use genetics to tell what continent or country people come from, this is the first study to be able to pinpoint people to regions within countries, says Leslie.

"Nobody has been able to see differences on this scale before," he says.

Despite some distinct groupings, however, the researchers found most of England was genetically very similar.

"Central and southern England, along with the north-eastern coast was relatively homogenous compared to everything else," says Leslie.

"It's pretty striking we can't separate out places like East Anglia and Kent."

Saxon invasion

By comparing DNA in the United Kingdom and Europe, the researchers were able to trace the movements of people into the UK and determine the ancestry of the English.

One of the key findings, says Leslie, is that the people in the homogenous area of England shared genetic markers with those from the Saxon area of northern Germany, providing strong evidence for 5th century Saxon invasion.

"It's quite striking the genetic clustering we observe relates so closely to known historical event," he says. "It's incredibly surprising we could pull this out. Nobody has ever tried an analysis like this before."

Saxon genetic markers were not present in the Welsh and Scots, he says. Leslie says the study helps inform an ongoing controversy over what happened to the ancient Britons when the Saxons invaded in the wake of the Romans during the Dark Ages.

"Some people speculate the Saxons completely replaced the ancient Britons, pushing them to into places such as Wales, Cornwall and Scotland," he says.

Leslie says this is supported by the recorded changes in language, place names, cereal crops, and pottery that coincided with the Saxon invasion.

However, the genetic study suggests while such cultural changes may have been imposed by those in power, everyday ancient Britons did not necessarily get displaced.

The results show the German or Saxon-like ancestry of the homogenous area of England is only between 10 and 40 per cent, which suggests the invaders interbred with the locals.

"That answers an age-old question," says Leslie.

Roman legacy

Leslie says the part of England invaded by Saxons was also previously the most heavily Romanised part of England.

The researchers speculate that the Romans developed a culture that was much more interconnected so that when the Saxons invaded, there were no barriers to the flow of people from one area to another.

"We know the Saxons had independent kingdoms but we don't see any of these," says Leslie.

"We speculate that that may well be because of the breakdown of geographic barriers."

Leslie emphasises people do not need to move far for DNA to spread a long way.

"All it takes is the girl in one village to marry the boy in the next village and for them to have a child who marries the girl in the next village and over generations DNA just moves," he says.

The study also challenges the notion of there being a single Celtic Britain.

"In fact the so-called Celtic parts of the UK -- Scotland, Northern Ireland, Wales and Cornwall -- are some of the most different from each other genetically," says Leslie.

His study showed those in the Orkney Islands are the most genetically distinct group in the UK, with clear genetic roots in Norway -- which is not surprising given they are a small isolated population that was once taken over by the Norwegian Vikings.