Archaeologists and environmental scientists from the University of Bradford, University of Leeds, University College Cork, and Queen's University Belfast have shown that changes in Late Bronze Age climate occurred after the fall in population. Their results show that human activity starts to decline after 900 BCE, and falls rapidly after 800 BCE, whereas climate records show that colder, wetter conditions didn't occur until around two generations later.
     The team used new statistical techniques to analyse more than 2000 radiocarbon dates taken from hundreds of archaeological sites in Ireland to pinpoint the precise dates that Europe's Bronze Age population collapse occurred. They then analysed past climate records from peat bogs to see if the dates tallied, and compared that with evidence of climate change across northwestern Europe between 1200 and 500 BCE.
     "Our evidence shows definitively that the population decline in this period cannot have been caused by climate change," says Ian Armit, Professor of Archaeology at the University of Bradford, and lead author of the study.
     Graeme Swindles, Associate Professor of Earth System Dynamics at the University of Leeds, added, "We found clear evidence for a rapid change in climate to much wetter conditions, which we were able to precisely pinpoint to 750 BCE using statistical methods."
     According to Professor Armit, social and economic stress is more likely to be the cause of the sudden and widespread fall in numbers. Communities producing bronze needed to trade over very large distances to obtain copper and tin. Control of these networks enabled the growth of complex, hierarchical societies dominated by a warrior elite. As iron production took over, these networks collapsed, leading to widespread conflict and social collapse. It may be these unstable social conditions that led to the population collapse at the end of the Bronze Age.
     According to Katharina Becker, Lecturer in the Department of Archaeology at University College Cork, the Late Bronze Age is usually seen as a time of plenty, in contrast to an impoverished Early Iron Age. "Although climate change was not directly responsible for the collapse it is likely that the poor climatic conditions would have affected farming," adds Professor Armit. "This would have been particularly difficult for vulnerable communities, preventing population recovery for several centuries."

Edited from ScienceDaily (17 November 2014)