Researchers at the University of Bern have successfully dated a prehistoric agricultural settlement in northern Greece to between 5328 and 5140 BC using dendrochronology and a significant radiocarbon spike in 5259 BC from a cosmic event known as the Miyake Event. This breakthrough provides a precise chronological reference for other archaeological sites in southeastern Europe and marks a paradigm shift in the way prehistoric dates are determined, especially in areas without consistent tree rings.
Scientists used dendrochronology and a radiocarbon spike from 5259 BC to date prehistoric Greek settlement to more than 7,000 years ago. This new method enables accurate dating for other archaeological sites in South-Eastern Europe.
For the first time, scientists from the University of Bern have precisely dated the prehistoric settlement of early farmers in northern Greece to more than 7,000 years ago. They achieved this by combining tree ring measurements on wooden building elements with a significant increase in cosmogenic radiocarbon dated to 5259 BC. This method provides a reliable chronological reference point for a number of other archaeological sites in southeastern Europe.
Dating finds plays a key role in archaeology. It is always essential to find out how old a tomb, settlement or individual object is. It is only possible to determine the age of prehistoric finds by a few decades. Two methods are used for this: dendrochronology, which allows dating based on sequences of tree rings, and radiocarbon dating, which can calculate the approximate age of finds based on the decay rate of the radioactive carbon isotope. 14C contained in annual rings.
The team led by the Institute of Archaeological Sciences at University of Bern have now been able to accurately date wood from the archaeological site of Dispilio in northern Greece, where dating to a year earlier was not possible, to various building activities between 5328 and 5140 BC. Scientists have used high-energy particles from space that can be reliably dated to 5259 BC. Their research was published May 20 in the journal The nature of communication.
Chronology of tree rings a 14Method C has its limits
Dendrochronology uses characteristic patterns of wide and narrow rings in wood that are influenced by climatic conditions. As a result, a wooden object can be dated by comparing the tree ring widths to pre-existing standard or regional chronologies.
“In Central Europe, there is a ring chronology that goes almost 12,500 years into the past – to 10,375 BC. However, this chronology only applies to certain regions. There is no consistent chronology for the Mediterranean area,” says lead study author Andrej Maczkowski from the Institute of Archaeological Sciences at the University of Bern.
Therefore, dendrochronological dating from this area must be classified as “floating” using radiocarbon dating. As long as the tree is alive, it absorbs the radioactive isotope 14C (radiocarbon) contained in the earth’s atmosphere via photosynthesis. When it dies, it no longer absorbs 14C; the isotope decays with a half-life of 5730 years. A laboratory measurement method can then be used to determine the quantity 14C is still contained within the particular tree ring, so calculate the approximate time of death of the tree during the known half-life. “However, accuracy such classifications are decades apart at best,” says Maczkowski.
Mass field at Dispilio site. Nearly 800 piles, mainly made of juniper and oak wood, were collected and dendrochronologically measured. This data forms the basis for the highly accurate dating of this site. Dispilio is the first archaeological site to be dated to an exact year using the Miyake event of 5259 BC. Credit: Dispilio Excavation Archive
“Until recently, therefore, dendrochronological dating to the year was believed to be possible only if a continuous regional year-ring chronology was available, which is the case for prehistoric periods in only three areas of the world: the southwestern United States, the northern Alpine foothills, and England/Ireland, ” explains Albert Hafner, professor of prehistoric archeology at the University of Bern and lead author of the study.
A paradigm shift thanks to a Japanese physicist
In 2012, a solution to the problem emerged: Japanese physicist Fusa Miyake discovered that a massive influx of cosmic rays, likely from solar flares, could cause the atmosphere to rise. 14The content of C, which is stored in annual rings. These spikes can be precisely dated based on long tree-ring chronologies, and because they are global events, they are important anchor points, especially in areas without consistent tree-rings.
“Miyake recognized the first anchor points of this kind and brought about a paradigm shift in prehistoric archaeology,” says Albert Hafner. Today there are a dozen of them Miyake events they are known up to 12,350 BC and two important events in 5259 and 7176 BC were only discovered in 2022 by researchers from ETH Zurich. No similar events of similar magnitude have been recorded in the last few centuries. If an event of the magnitude of 5259 BC were to occur today, it would likely have a catastrophic impact on telecommunications and electronics.
The Miyake event allows dating in Dispilio
A research team from the EXPLO project led by the University of Bern managed to create an annual growth ring chronology spanning 303 years ending in 5140 BC by analyzing 787 pieces of wood from the archaeological site of Dispilio near Lake Orestida in northern Greece. . The identified settlement phases show various house building activities over the course of 188 years between 5328 and 5140 BC. This exact dating is possible because the famous Miyake event occurred during this period in 5259 BC.
Researchers from ETH Zurich were able to detect an increase in radiocarbon content during this time by radiocarbon dating several individually defined annual growth rings. So it was a matter of reproducing this peak, reflected globally in the tree-ring chronologies of Siberian larch, American pine, and European oak, on the tree-ring chronology from Dispilio, Greece, and connecting it to the anchor point of 5259 BC. “The Balkans is therefore the first region in the world to benefit from this paradigm shift and is able to successfully determine absolute dating independently of a consistent calendar,” says Albert Hafner.
Andrej Maczkowski adds: “We expect that other chronologies for the region from this period can now be linked in quick succession to the ‘Dispilio Chronology’. This paves the way for the development of a regional dendrochronology for the southern Balkans. “The Balkans are home to the oldest lakeside settlements in Europe, the sites of which are dated to just after 6000 BC. The region played a key role in the expansion of agriculture in Europe.
Link: “Absolute dating of the European Neolithic using a rapid 14C 5259 BC excursion” by Andrej Maczkowski, Charlotte Pearson, John Francuz, Tryfon Giagkoulis, Sönke Szidat, Lukas Wacker, Matthias Bolliger, Kostas Kotsakis, and Albert Hafner, May 20, 2024 The nature of communication.
DOI: 10.1038/s41467-024-48402-1