Using new methods for analysing DNA variation that provide a less biased picture of diversity, and a better estimate of the timing of population events, a team led by Professor Mark Jobling from the University of Leicester's Department of Genetics sequenced a large part of the Y chromosome, passed exclusively from fathers to sons, in 334 men from 17 European and Middle Eastern populations. The genealogical tree they traced reveals three very young branches, whose shapes indicate recent expansions which account for the Y chromosomes of 64 percent of the men studied.
     Estimates of past population sizes show populations from the Balkans to the British Isles underwent an explosion in population during the Bronze Age, between 2,000 and 4,000 years ago. This contrasts with earlier results for the Y chromosome, and also with the picture presented by maternally-inherited mitochondrial DNA, which suggests much more ancient population growth.
     Previous research has focused on the proportion of modern Europeans descending from Palaeolithic hunter-gatherer populations or more recent Neolithic farmers, reflecting a transition that began about 10,000 years ago.
     Chiara Batini, also from the University of Leicester's Department of Genetics, and lead author of the study, adds: "Given the cultural complexity of the Bronze Age, it's difficult to link a particular event to the population growth that we infer. But Y-chromosome DNA sequences from skeletal remains are becoming available, and this will help us to understand what happened, and when."

Edited from Popular ARchaeology (19 May 2015), The Telegraph (20 May 2015)