Most European men today can trace their genetic roots to just a small group of Bronze Age forefathers, the result of a "population explosion" thousands of years ago, a DNA study suggests.

Researchers analyzed genetic data on 334 men from 17 different European and Middle Eastern populations, focusing on DNA sequences making up large portions of the Y chromosome, which is passed exclusively from fathers to sons and so can be used to trace paternal lines down through time.

The analysis reveals two out of three European men today are descended from just three paternal lineages, fairly young branches on the genealogical tree of European Y chromosomes, the researchers write in the journal Nature Communications.

Those young branchings suggest an explosion in the male population between 2,000 and 4,000 years ago, a period of social, economic and technological advances, researchers say.

"The population expansion falls within the Bronze Age, which involved changes in burial practices, the spread of horse-riding and developments in weaponry," says study leader Mark Jobling, a geneticist at the University of Leicester in England.

"Dominant males linked with these cultures could be responsible for the Y chromosome patterns we see today," he says.

The researchers say their genetic findings suggest the spread of modern populations in Europe took place much later than has previously been assumed.

It has been believed those populations began to expand during the Palaeolithic period as hunter-gatherers spread out across the continent; however, the new study is evidence most modern populations appear to have settled in Europe after the spread of farming during the later Neolithic period.

One of the mutations linked to modern European men has been dated to between 3,700 and 6,500 years ago and spread through what is today Spain, France, Italy and England.

Another, dating to around the same time, is prominent today in Lapland, the Netherlands, Hungary, Serbia and Bavaria.

The DNA study could help scientists and historians fill in a picture of how the three identified paternal lineages spread across Europe, the researchers say.

 "Given the cultural complexity of the Bronze Age, it's difficult to link a particular event to the population growth that we infer," says study co-author Chiara Batini, also a University of Leicester geneticist.

"But Y-chromosome DNA sequences from skeletal remains are becoming available, and this will help us to understand what happened, and when."

The three individuals who fathered the paternal lines still seen today were likely powerful or influential individuals, the researchers explain, because such people would have traveled more widely during the Bronze Age and probably fathered many more children than other men, enough children for their lineage to survive and spread.

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