In the 940s when the Byzantine Empire was at the peak of its power and the Vikings sailed the seas, one tiny seedling sprouted up in Greece. More than a thousand years later today, Europe is already a different place but the seedling, now a grown-up tree, remains standing.

Scientists said that a Bosnian pine (Pinus heldreichii) that thrives in the highlands of northern Greece is more than 1,075 years old. Nicknamed "Adonis," the tree is now considered the oldest single tree and oldest living organism in Europe, having survived many of the iconic events in history that most humans only read about in books such as the Crusades, the Protestant Reformation and world wars.

Researchers were able to determine the age of the tree using dendrochronology, or tree-ring dating, which uses a scientific approach to analyze the pattern of tree rings, also called growth rings.

The researchers conducted dendrochronological studies by taking tree cores from which they could count the tree rings. The process does not pose risk to the health of trees. The cores are only about 5 millimeters (around 0.2 inches) in diameter so Adonis was not endangered when the scientists conducted their study. The researchers then counted the growth rings and then compared nearby trees to one another to identify anomalies.

"To age the tree, we needed to take a core of wood, from the outside to the center. The core is 1 meter [3.28 feet] and has 1,075 annual rings," said Paul Krusic, who led the expedition that found the tree.

The research expeditions were conducted by the Navarino Environmental Observatory (NEO), which conducts studies on climate change and its effect on environment and humans.

The analysis revealed the pine is at least 1,075 years old. Although elderly trees are relatively common in other parts of the globe, they are rare in Europe. The reason behind this is the presence of humans. Trees are more likely to be chopped down and used as firewood and construction material or to give way for development with more human traffic in a region.

Scientists said that the annual variation of the growth rings from trees such as Adonis — and those that have fallen in centuries past that remain preserved on the ground — will hopefully give information about historical climatic and environmental conditions that go back thousands of years.

"That has a story in it. A story about climate change, about human influences," Krusic said. "That's the real story we're working on. This is just something we stumbled upon."

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