Researchers from the University of Bern have achieved a groundbreaking feat by precisely dating a prehistoric agricultural settlement in northern Greece, which is over 7,000 years old. Utilizing a combination of annual growth ring measurements in wooden construction elements and a sudden spike in cosmogenic radiocarbon dating back to 5259 BC, they have provided a reliable chronological reference for numerous archaeological sites in Southeastern Europe.

Dating archaeological finds is crucial in understanding historical timelines. Determining the age of a tomb, settlement, or specific object has only been possible for a few decades, thanks to two methods: dendrochronology and radiocarbon dating.

Now, the archaeological site of Dispilio in northern Greece, previously undatable with precision, has now been dated with activities ranging from 5328 to 5140 BC. The researchers used high-energy particles from space, which can be reliably dated to 5259 BC. Their findings have been published in Nature Communications.

Prehistoric lakeside settlements from the period 5700 - 500 BC in Albania, Greece and North Macedonia
Prehistoric lakeside settlements from the period 5700 – 500 BC in Albania, Greece and North Macedonia. Credit: Andrea Bieri / University of Bern

Dendrochronology relies on characteristic patterns of wide and narrow annual growth rings in wood, influenced by climatic conditions. By comparing these patterns with existing standard or regional chronologies, an object’s age can be determined. However, this method is region-specific and does not apply universally, particularly in the Mediterranean region, where a coherent chronology is lacking.

Therefore, dendrochronological dating in this region is classified as “floating” and requires radiocarbon dating. As a tree lives, it absorbs 14C from the atmosphere through photosynthesis. Upon death, the absorption stops, and the isotope decays with a half-life of 5730 years.

Laboratory measurements can then determine the remaining 14C in a specific tree ring to approximate the time of the tree’s death. However, this method’s accuracy is limited to within decades.

The prehistoric site of Dispilio is located on Lake Kastoria in northern Greece. The town of Kastoria can be seen in the background. At the bottom center of the picture is the modern reconstruction of a prehistoric pile dwelling
The prehistoric site of Dispilio is located on Lake Kastoria in northern Greece. The town of Kastoria can be seen in the background. At the bottom center of the picture is the modern reconstruction of a prehistoric pile dwelling. Credit: Marco Hostettler / University of Bern

In 2012, Japanese physicist Fusa Miyake identified a solution to this problem. A massive influx of cosmic rays, likely from solar eruptions, can cause a significant increase in atmospheric 14C, which is deposited in the tree rings of that year.

These spikes, now known as Miyake events, can be precisely dated and serve as global chronological anchors. Today, about a dozen Miyake events are known, with significant ones occurring in 5259 BC and 7176 BC, discovered by researchers from ETH Zurich in 2022.

The team from the University of Bern’s EXPLO project established an annual growth ring chronology spanning 303 years, ending in 5140 BC, by analyzing 787 wood pieces from the Dispilio archaeological site at Lake Orestida. The identified settlement phases show diverse construction activities over 188 years between 5328 and 5140 BC. This precise dating was made possible due to a known Miyake event in 5259 BC.

Microscope photo of the actual tree-rings where the Miyake event of 5259 BC was detected. The
Microscope photo of the actual tree-rings where the Miyake event of 5259 BC was detected. The “event ring” is right below the ring which has a series of double dots. To the naked eye the “event ring” is not in any way different than the other rings, since the Miyake event would have not influenced the anatomy of trees. The width of the razor blade in the background is 1.8 cm. Credit: Andrej Maczkowski / University of Bern

Researchers from ETH Zurich detected a radiocarbon peak during this period by radiocarbon dating several individually defined annual growth rings. This peak was then mirrored in the Dispilio tree ring chronology, aligning with the global 5259 BC anchor point. Consequently, the Balkans have become the first region to benefit from this paradigm shift, achieving absolute dating independently of a consistent calendar.

Andrej Maczkowski, a lead researcher, hopes other regional chronologies from this period can now link to the “Dispilio Chronology”, paving the way for developing a regional dendrochronology for the southern Balkans.

This region, home to Europe’s oldest lake settlements dating back to shortly after 6000 BC, played a crucial role in the spread of agriculture across Europe.


Sources

University of Bern | Maczkowski, A., Pearson, C., Francuz, J. et al. Absolute dating of the European Neolithic using the 5259 BC rapid 14C excursion. Nat Commun 15, 4263 (2024). doi.org/10.1038/s41467–024–48402–1


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