http://news.nationalgeographic.com/news/2005/07/0719_050719_ britishgene_2.html
British Have Changed Little Since Ice Age, Gene Study Says
Stonehenge Manpower
Britain's population in the late Stone Age may have much been larger than historians once supposed. For instance, scientists have calculated that it would have taken around 30 million hours to create Stonehenge.
"By the time Stonehenge was built you'd had about a thousand years of farming," Miles said. "The population's expanding, and people are getting together to form big labor forces to put up these big public buildings."
Population estimates based on the size and density of settlements put Britain's population at about 3.5 million by the time Romans invaded in A.D. 43.
Many historians now believe subsequent invaders from mainland Europe had little genetic impact on the British.
The notion that large-scale migrations caused drastic change in early Britain has been widely discredited, according to Simon James, an archaeologist at Leicester University, England.
"The gene pool of the island has changed, but more slowly and far less completely than implied by the old invasion model," James writes in an article for the website BBC History.
For the English, their defining period was the arrival of Germanic tribes known collectively as the Anglo-Saxons. Some researchers suggest this invasion consisted of as few as 10,000 to 25,000 peoplenot enough to displace existing inhabitants.
Analysis of human remains unearthed at an ancient cemetery near Abingdon, England, indicates that Saxon immigrants and native Britons lived side by side.
"Probably what we're dealing with is a majority of British people who were dominated politically by a new elite," Miles said. "They were swamped culturally but not genetically."
Genetic Continuity
"It is actually quite common to observe important cultural change, including adoption of wholly new identities, with little or no biological change to a population," Simon James, the Leicester University archaeologist, writes.
One such change is the emergence of a Celtic identity in Britain. There are no historical references to Celts in ancient Britain.
Miles explained that "Celts" was a name applied to tribes in Gaulmodern-day Francethough their language shared the same root as those spoken by British tribes.
"In the 18th and 19th centuries, as Ireland, Wales, and Scotland started to assert national identity, they began to talk about themselves as Celts," Miles added.
Miles acknowledged that the techniques used to explore genetic ancestry are still in their infancy and that many more samples are needed to fully understand the origins of the British people.
"By mapping the genetic variability of humans around the world, geneticists can begin to track their dispersal, migrations, and interrelationships," Miles writes