The ancestors of modern Scottish people left behind mysterious, carved stones that new research has just determined contain the written language of the Picts, an Iron Age society that existed in Scotland from 300 to 843.

The highly stylized rock engravings, found on what are known as the Pictish Stones, had once been thought to be rock art or tied to heraldry. The new study, published in the Proceedings of the Royal Society A, instead concludes that the engravings represent the long lost language of the Picts, a confederation of Celtic tribes that lived in modern-day eastern and northern Scotland.

“We know that the Picts had a spoken language to complement the writing of the symbols, as Bede (a monk and historian who died in 735) writes that there are four languages in Britain in this time: British, Pictish, Scottish and English,” lead author Rob Lee told Discovery News.

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