Researchers from the University of Bern have successfully dated a prehistoric farming 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 from southeastern Europe and marks a paradigm shift in the way prehistoric dates are determined, especially in areas without a consistent tree-ring chronology.
Researchers used dendrochronology and a radiocarbon dating of 5,259 BC to date a prehistoric Greek settlement to more than 7,000 years ago. This new method makes it possible to accurately date other archaeological sites from Southeast Europe.
Researchers from the University of Bern have for the first time accurately dated a prehistoric settlement of early farmers in northern Greece to more than 7,000 years ago. They achieved this by combining annual growth ring measurements on wooden building elements with a significant jump in cosmogenic radiocarbon dating to 5259 BC. This method provides a reliable chronological starting point for many other archaeological sites in Southeastern Europe.
Dating finds plays a key role in archaeology. It is always essential to find out how old a given tomb, settlement or individual site is. Determining the age of finds from prehistoric times has only been possible for a few decades. Two methods are used for this: dendrochronology, which allows dating based on sequences of annual rings in trees, and radiocarbon dating, which can calculate the approximate age of finds by the rate of decay of the radioactive carbon isotope 14C contained in tree rings.
A team led by the Institute of Archaeological Sciences at University of Bern has now been able to accurately date timber from the archaeological site of Dispilio in northern Greece, where dating to the year before was not possible, to various building activities between 5328 and 5140 BC. The researchers used high-energy particles from space that could be reliably dated to 5259 BC. Their research was published May 20 in the journal Nature Communications.
Tree ring chronologies and 14The C method has its limits
Dendrochronology uses characteristic patterns of wide and narrow annual growth rings in a tree that are influenced by climatic conditions. As a result, a wooden object can be dated by comparing the width of annual growth rings with already existing standard or regional chronologies.
“There is a chronology of tree rings in Central Europe that goes almost 12,500 years back into the past – to 10,375 BC. However, this timeline only applies to certain regions. There is no consistent chronology for the Mediterranean region,” says lead study author Andrei Mackovski of the Institute of Archaeological Sciences at the University of Bern.
Dendrochronological dating from this region should therefore be classified as “floating” using radiocarbon dating. As long as a tree is alive, it absorbs the radioactive isotope 14C (radiocarbon) contained in the earth’s atmosphere through photosynthesis. When it dies, it no longer absorbs 14° C; the isotope decays with a half-life of 5730 years. A laboratory measurement method can then be used to determine how much 14C is still contained in a particular tree ring and thus the approximate time of death of the tree for the known half-life is calculated. “Whatever accuracy of such classifications is within decades at best,” says Maczkowski.
The stake field at Dispilio’s place. Almost 800 piles, mostly of juniper and oak wood, were sampled and dendrochronologically measured. This data forms the basis for the high-precision 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, dendrochronological dating to the year was thought to be possible only if a continuous regional tree-ring chronology was available, which is the case for prehistoric periods in only three regions 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 senior 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, possibly due to solar flares, could cause the atmosphere to rise 14C content deposited in the tree rings of the respective years. These spikes can be accurately dated based on long tree-ring chronologies, and because they are global events, they are important reference points, especially in regions without consistent annual growth-ring chronologies.
“Miyake recognized the first footholds of this kind and thereby led to a paradigm shift in prehistoric archaeology,” says Albert Hafner. Today a dozen of them Events in Miyake are known until 12,350 BC, and the two important events in 5259 and 7176 BC were only discovered in 2022 by researchers at ETH Zurich. No similar events of this 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 effect on telecommunications and electronics.
The Miyake event allows dating in Dispilio
The research team from the EXPLO project, led by the University of Bern (see box), was able to establish an annual growth ring chronology spanning 303 years, ending in 5140 BC, by analyzing 787 pieces of wood from the archaeological site of Dispilio on Lake Orestida in northern Greece. The settlement phases identified show various house building activities over 188 years between 5328 and 5140 BC. This exact dating is possible because there was a known event in Miyake during this period in 5259 BC.
Researchers from ETH Zurich were able to detect a jump in radiocarbon content during this time by radiocarbon dating several individually defined annual growth rings. It is therefore a question of replicating this peak, which is reflected globally in the annual growth ring chronology of Siberian larch, American pine and European oak, onto the annual growth ring chronology from Dispilio in Greece and linking it to pivot 5259 BC . “The Balkans are therefore the first region in the world to take advantage of this paradigm shift and successfully establish absolute dating independently of a sequential calendar,” says Albert Hafner.
Andrei Mackovski adds: “We expect that other chronologies for the region from this period can now be linked to the ‘Dispilio Chronology’ in quick succession.” This paves the way for the development of a regional dendrochronology for the southern Balkans. “The Balkans have the oldest coastal settlements in Europe, the sites of which have been dated to shortly after 6000 BC. The region plays a key role in the expansion of agriculture in Europe.
Reference: “Absolute dating of the European Neolithic using the 5259 BC 14C rapid excursion” by Andrej Mackovski, Charlotte Pearson, John French, Trifon Giagkoulis, Sjonke Sidat, Lukas Wacker, Mathias Bolliger, Kostas Kotsakis, and Albert Hafner May 20, 2024 Nature Communications.
DOI: 10.1038/s41467-024-48402-1
