Archaeologists and environmental scientists from UCC, the University of Bradford, University of Leeds, and Queen’s University Belfast have shown that the changes in climate that scientists believed coincided with the fall in population in fact occurred at least two generations later.
Their results, published today in Proceedings of the National Academy of Sciences, show human activity started to decline after 900BC, and fell rapidly after 800BC, indicating a population collapse. However, the climate records show colder, wetter conditions didn’t occur until about two generations later.
Fluctuations in levels of human activity are reflected by the numbers of radiocarbon dates for a given period. The team used new statistical techniques to analyse 2,000 radiocarbon dates, taken from hundreds of archaeological sites in Ireland, to pinpoint the precise dates Europe’s Bronze Age population collapse occurred.
“We are in the lucky position to have in Ireland a large set of well-dated sites that were excavated during the years of the Celtic Tiger to facilitate road, pipeline, and housing developments. From an archaeological perspective, this selection of sites effectively provides a representative sample of past activity across the country,” says Dr Katharina Becker of UCC’s archaeology department. She lectures and specialises in the archaeology of Late Bronze Age and Iron Age Ireland.
The team then analysed past climate records from peat bogs in Ireland and compared the archaeological data to these climate records to see if the dates tallied. That information was then compared with evidence of climate change across north-west Europe between 1200 and 500 BC.
“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 Earthsystem 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 750BC using statistical methods.”
According to Prof Armit, social and economic stress is more likely to be the cause of the sudden and widespread fall in numbers.
The findings have significance for modern-day climate change debates which, argues Prof Armit, are often too quick to link historical climate events with changes in population.