New technology reveals a star-shaped burn mark hidden under peat that gives clues to the meaning of the standing stones on Lewis

For thousands of years the Callanish standing stones erected on the remote Hebridean island of Lewis have remained a mystery. Why were they placed there? And for what purpose?

Now archaeologists have uncovered dramatic new evidence that suggests our Neolithic ancestors were inspired to construct the megaliths as devotional monuments by the natural phenomenon of lightning strikes. A geophysical survey around one of the stones has astonished archaeologists by revealing a star-shaped pattern formed by one, or possibly multiple, earth-shaking lightning strikes. New technology has exposed a clear pattern covering an area of up to 20 metres in diameter, buried until now beneath peat bogs.

The single stone, within “site XI”, is about 2.8km from the famous Callanish great circle in the island’s Loch Roag area. Geophysical techniques have mapped buried features and the new evidence shows that this 1.5-metre-high stone was originally part of another circle with the lightning strike pattern at its centre. The stones’ original positions have been revealed as magnetic anomalies in the survey.

“We’re really excited,” said professor Vincent Gaffney, one of the archaeologists. “This was completely and utterly unexpected. Seeing the evidence for a massive strike, right in the middle of what now seems to be a stone circle, is remarkable.”

He added that such a lightning strike may have hit an upstanding feature – perhaps a tree or a rock – in “a prehistorical equivalent of an act of God”: “It does rather look as if lightning was part of the game in creating this stone circle.”

A geophysical survey revealed a star-shaped lightning strike in the middle of what seems to have been a circle of standing stones. Their original positions, marked in red, have been revealed as magnetic anomalies in the survey. Photograph: Richard Bates

Dr Richard Bates, a geoscientist at St Andrews University, who is leading the project, described the discovery as highly exciting. He said: “We’re finally getting new results on these places because of new technologies, allowing us to look at standing stones in a whole new light.”

The Callanish great circle is thought to have been erected in 3,000 BC, some 500 years before the major stone settings at Stonehenge, which is linked with another natural event: the solstices. More than 15 other sites on the island have been identified as possible satellite circles.

With the geophysical survey, determining the chronology is difficult, said Bates. “Did the lightning strike come first or did the building of the stone circle come first? The lightning strike occurred before peat started forming So we know it’s pre-peat, which started to form around 3,000 years ago. It seems more than coincidence that these are occurring in the same place.”

Gaffney, from Bradford University’s department of archaeological sciences, has also headed the Stonehenge Hidden Landscapes project, surveying land around the Wiltshire monument.

He described the new geophysical evidence as “phenomenal”: “We’ve never seen this before. It just says so much about how our ancestors related to nature. It is not a great leap of the imagination to believe early societies would have been enamoured with natural events. Standing stones are linked, for instance, to astronomic events. Remember what Jove used as a weapon – lightning bolts. This is something which occurs in a number of religions. So we can identify here a rule of nature perhaps informing or reinforcing belief structures in the past.”

Gaffney’s brother, Dr Chris Gaffney, an archaeological geophysicist, said that it was impossible to see the fossilised lightning strike by just walking across the site. “You literally have to peel back all of the peat potentially to see the scarring on the bedrock.”

He added that the evidence suggests that the stones sanctified the spot of “a really huge-looking event”: “The prospect of understanding why a particular stone circle might be in a particular location is amazing. We’re always trying to get into other people’s heads when we’re thinking of these ancient ritual sites. Well, we might now have an idea.”