The European economy started to collapse 2,900 years ago, not because of dodgy banking practices but following the break-up of trade. Bronze went out of fashion in favour of iron and the business activity that had built up around the metal quickly fell apart, research from Irish archaeological sites has shown.

Researchers have long pinned the blame for a huge pan-European population collapse after 900BC on climate change. Irish site and climate records from peat bogs show, however, the colder, wetter weather didn’t arrive until at least two generations after the collapse had started.

Ironically we have the Celtic tiger economy to thank for the information used to make these claims, said Dr Katharina Becker, a lecturer in the department of archaeology at University College Cork. The building boom opened up archaeological sites under pipelines, housing and roads. This was used in a study involving UCC, the universities of Bradford and Leeds, and Queen’s University Belfast that is published this evening in the US Proceedings of the National Academy of Sciences. “Our evidence shows definitely that the population decline in this period cannot have been caused by climate change,” said lead author prof Ian Armit of the University of Bradford.

The team found the change in weather started about 750BC. The population fall started after 900BC and accelerated rapidly after 800BC, the researchers found. The evidence also suggests it was an economic collapse and not war, famine or disease that caused the fall in populations across Europe, including Ireland.

Iron age

“The basis of their power and wealth would have vanished,” Dr Becker said. “We believe this was a general economic crisis caused by the break-up or reduction in trade connections.”

Conflict and social collapse would have followed, giving way to an impoverished early iron age. Large-scale construction also stopped, putting an end to the building of major ring forts such as Dún Aonghasa on the Aran islands.