The mysterious assemblage of 25-ton rocks at Stonehenge usually steals the show. But the ground beneath the stones holds secrets, too – 5,000 years ago, this patch of land in Wiltshire, in southern England, was a burial place. And some of the ancient human remains found at Stonehenge have unusually distant origins, according to a new archaeological study of cremated bones published Thursday in the journal Scientific Reports.

The remains offer another line of evidence connecting Stonehenge to Wales, 140 miles away. A quarry in Wales is probably the source of Stonehenge’s bluestones, so called because of their blue hue revealed when they are damp or broken. It is possible, the authors of the new study say, that people buried at the henge came from the same Welsh region.

Christophe Snoeck, a researcher at Vrije University in Belgium who specializes in archaeology and chemistry, helped lead the study of 25 people buried at Stonehenge and found that they were from distant lands. “Forty percent of the people who we analyzed could not have lived in Stonehenge for the last decade or so of their life,” Snoeck said.

A chemical analysis of their bones indicates that 10 of the 25 people were not locals. This was at a time when, before the invention of the wheeled transport, most people stayed within a few kilometers of their settlements, Snoeck said. “I know today everyone moves around, but we’re talking 5,000 years ago,” he said.

The beginnings of this study can be traced back to the 1920s, when archaeologists first excavated pits at Stonehenge called Aubrey holes, named after 17th century natural philosopher John Aubrey. The archaeologists identified 58 Neolithic individuals in 56 Aubrey holes. But those archaeologists reburied bone fragments in a single hole, creating a jumble that Snoeck likened to a mess of ribs charred together in a post-barbecue fire.

After a team re-excavated the remains in 2008, Snoeck’s co-author Christie Willis, at the University College London’s Institute of Archaeology, began the difficult work of identifying individuals from the jumble. She was successful in 25 cases.

Snoeck, meanwhile, was developing a technique to identify the element strontium, a metal deposited in bedrock, within cremated remains. Plants absorb strontium from the soil. It accumulates in bones when people eat plants.

Archaeologists can detect different versions of strontium, called isotopes, preserved in tooth enamel. This gives researchers a sense of where deceased people lived. “The strontium is usually related to the underlying geology,” said Jane A. Evans, an archaeologist at the British Geological Survey who was not involved with this research, “and this gives us geographic information.” Evans had previously mapped different strontium isotopes across the United Kingdom for this purpose.

But cremated remains were generally considered an archaeological dead end, too damaged to yield information. Teeth have a bad habit of exploding when bodies are burned, Snoeck said.

Yet he refused to accept that cremated remains were totally inscrutable. “Not being able to extract information from them was leaving too many blank pages in our history, in our past,” Snoeck said.

For his PhD research, he developed a way to identify strontium in cremated bones from Northern Ireland. “Lots of people were telling me it’s never going to work,” he said. But burned bones, as it turns out, crystallize and become compact like teeth. And, like teeth, Snoeck discovered, they also trap strontium.

Working on cremated bone “opens up a whole new area of study in adult migration that was not previously possible,” Evans said. Strontium collects in tooth enamel formed in childhood; strontium in bones should give a snapshot of the last 10 to 15 years of a person’s life.

When archaeologists sent Stonehenge remains to Snoeck’s lab for another project, he jumped at the chance to apply his technique to them. The Wessex chalk beneath Stonehenge, which stretches for at least 9 miles in every direction, has a very specific strontium profile. Ten of the people did not match that type.

Those Neolithic bones did, however, match the strontium isotopes found in Wales. The analysis cannot prove that Welsh people built the monument. But the archaeological dates of the remains are close to the period of early Stonehenge construction.

“This suggests it was not just the stones that were brought to Wiltshire,” Evans said, “but there could have been a continuing link between the two areas.”

Snoeck said he doubts that the people were cremated near Wiltshire. The archaeologists who first excavated the Aubrey holes identified impressions of organic containers – leather bags, probably – in the soil. It’s more likely that travelers carried their deceased to this place, placing them to rest miles from home.

The archaeologist plans to study cremated remains in other countries. “They’ve been kind of forgotten and put aside. And I thought that was quite sad, because huge parts of the world” – in especially in prehistoric Europe, but not just there – “people were cremated,” he said.

His next project, called CRUMBEL, will trace cremation throughout history in Belgium, from ancient practices to its abandonment under the influence of the Catholic Church, which only relaxed its rules against cremation in 1963.