|13 November 2005
DNA shows first Europeans were hunters not farmers
The first farmers to arrive in Europe more than 7,000 years ago appear to have left behind a legacy of agriculture but no descendants, a study of ancient DNA has found. Modern Europeans do not seem to have inherited the genes of the first farmers to arrive from the Near East, where they had invented agriculture 12,000 years ago.
A study of 24 skeletons of an early farming community in central Europe has found that their DNA does not match the DNA of modern men and women living in the same part of the world. The researchers believe the findings indicate that although the first farmers brought agriculture to Europe, they did not manage to displace the much older, resident population of hunter gatherers.
In a paper published in the journal Science, the team concludes that modern Europeans are directly descended from the first modern humans to arrive on the continent more than 40,000 years ago when they survived on hunting game and gathering berries.
How the practice of farming spread across Europe and what happened to the people who were living on the continent at the time, has been a long-running debate in human prehistory. Some experts believe that the first farmers displaced the early hunter-gatherers because the improvements in food supply that agriculture provided led to an explosion in the population.
However the latest study by a team from Britain, Germany and Estonia suggests that the first farmers did indeed pass on the culture of farming but they did not contribute significantly to the overall genetic make-up of modern Europeans. "This was a surprise. I expected the distribution of mitochondrial DNA in these early farmers to be more similar to the distribution we have today in Europe," said Joachim Burger of Johannes Gutenberg University in Mainz, Germany. Mitochondrial DNA is passed on only from mothers to their children so it is possible that the latest results could still be explained by incoming farmers taking local women for their wives.
The team analysed the mitochondrial DNA of 24 skeletons - belonging to a culture known as the Linearbandkeramik - from 16 locations in Germany, Austria and Hungary. Six of these 24 skeletons contain genetic signatures that are extremely rare in modern European populations. Based on this discovery, the researchers conclude that early farmers did not leave much of a genetic mark on modern European populations.
The Linearbandkeramik were the first farmers known to occupy central Europe, notably the area of modern-day Hungary and Slovakia, about 7,500 years ago. Within the following 500 years, agriculture had spread west to France and east to the Ukraine. The archaeological evidence suggests that agriculture was introduced into Greece and south-east Europe from the Near East more than 8,000 years ago and then spread north and west towards the Atlantic.
One possible scenario is that small pioneer groups of farmers moved into an area occupied by hunter-gatherers who quickly changed their lifestyle once they saw the benefits of growing their own crops. Alternatively, a different population may have replaced the early farmers but the archaeological evidence for such a mass and rapid displacement is scant.
"This study does not resolve the puzzle, but their interpretation is in line with what a lot of people have been suggesting for quite some time," says Antonio Torroni, a geneticist from the University of Pavia, Italy. But Terry Brown, a geneticist from the University of Manchester, UK, calls the conclusions "a little bit tenuous". Brown points out that the study examines events in only one geographic region. "During the 3,000 years in which agriculture spread into Europe, many different things were happening," says Brown. In some areas, hunter-gatherers probably picked up farming quickly; in others, farmers may have overrun the locals. "I don't think you can generalize," he says. Researchers on both sides say the debate could be clarified by data from the bones of the hunter-gatherers. But viable DNA from such bones is in very short supply.
Sources: Nature.com (10 November 2005), AAAS News Release, The Independent (11 November 2005)
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