Researchers from the University of Bern have achieved a groundbreaking feat by precisely dating a prehistoric agricultural settlement in Northern Greece, believed to be over 7,000 years old.
By combining annual tree-ring growth data from wooden construction elements with a sudden spike in cosmogenic radiocarbon dated to 5259 BC, they have established a reliable chronological benchmark for numerous archaeological sites across Southeastern Europe.
Why Dating Archaeological Finds Matters
Accurately dating archaeological discoveries is crucial to understanding the timelines of human history. Only in recent decades has it become possible to determine the age of a tomb, settlement, or specific artifact thanks to two primary methods: dendrochronology (tree-ring dating) and radiocarbon dating.
Until now, the prehistoric settlement of Dispilio in Northern Greece had not been precisely dated. But researchers have now placed its human activity between 5328 and 5140 BC. Their results, published in Nature Communications, rely on high-energy particles from space — particularly from a known cosmic event in 5259 BC — to provide an absolute chronological anchor.
Tree-Ring Dating, Radiocarbon Dating — and the Problem They Faced
Dendrochronology is based on distinct patterns of wide and narrow annual rings in wood, which reflect climatic conditions. By comparing these patterns with established regional chronologies, researchers can estimate an object’s age. However, this method isn’t universally applicable — especially in the Mediterranean, where a consistent chronological sequence is lacking.
As a result, tree-ring chronologies in this region are considered “floating” and must be linked to radiocarbon dating. Trees absorb Carbon-14 (14C) from the atmosphere during their life through photosynthesis. When a tree dies, it stops absorbing 14C, which then begins to decay at a known rate (half-life of 5,730 years).
By measuring the remaining 14C in a specific ring, scientists can estimate the year of the tree’s death — but only within a margin of several decades. That’s where the challenge lay.
A Breakthrough: The Miyake Events
In 2012, Japanese physicist Fusa Miyake discovered a potential solution. A massive burst of cosmic rays, likely caused by solar flares, can trigger a sharp spike in atmospheric 14C, which becomes embedded in the tree rings of that specific year.
These spikes — now called Miyake Events — can be dated precisely and serve as global chronological anchors. Around a dozen such events are now known, with two major ones in 5259 BC and 7176 BC, the latter discovered in 2022 by researchers from ETH Zurich.
The team from the EXPLO project at the University of Bern constructed a 303-year-long tree-ring chronology ending in 5140 BC by analyzing 787 wood samples from the Dispilio archaeological site on Lake Orestiada (modern-day Lake Kastoria).
The settlement phases identified reveal construction activities spanning 188 years, from 5328 to 5140 BC — made possible by the anchoring provided by the Miyake Event of 5259 BC.
When the Trees Confirmed the Timeline
Researchers at ETH Zurich detected a significant radiocarbon spike during this period by dating several individual tree rings. This same spike was found in the Dispilio wood sequence, matching the global 5259 BC anchor point.
Thanks to this match, the Balkans have become the first region to benefit from this new chronological standard, allowing for absolute dating without relying on a continuous calendar.
"The Dispilio Chronology"
Andrej Maczkowski, lead researcher, hopes that more regional chronologies from the same period will soon be aligned with the “Dispilio Chronology,” opening the door to developing a regional tree-ring record for the southern Balkans.
This region, home to Europe’s oldest lakeside settlements, dating back to just after 6000 BC, played a pivotal role in the spread of agriculture across the continent.
