Researchers have found evidence that an unremarkable prehistoric burial mound near Bordeaux, in southwest France, was re-used by locals for around 2,000 years.
The researchers say what drew people to the mound for two millennia remains a mystery.
The Le Tumulus des Sables site was discovered by chance in 2006, when school children stumbled across human remains in their kindergarten playground.
Hannah James, a PhD candidate at The Australian National University (ANU), says it was initially assumed the site was used solely by the Bell Beakers, one of the first cultures to spread out across Europe.
"We now know people were actually coming back to this site and burying their dead in there again and again, from the Neolithic to the Iron Age," Ms James said.
"We're looking at remains from around 3600 BCE, all the way through to around 1250 BCE. All the bodies are really mixed up, and we're dealing with tiny fragments of bones.
"The tomb is unusual because it's not a really obvious site. It's a mound about 50 cm deep. It's not on a hill or an obvious location. So, there's something else about this site which caused people to come back and use it."
By using radiocarbon dating and stable isotope analysis (which help measure decay), the team was able to gather more information about the people buried there.
"Carbon and nitrogen isotopes tell us about what kind of food they were eating. They were eating food from the land. Strangely it doesn't look like they were hunting and gathering from the nearby river, or the ocean, which is 10 kilometres away," Ms James said.
"Oxygen and strontium isotopes tell us about mobility, where people were living during childhood when their teeth were forming".
The majority of analysed individuals have "a very local signature". But the evidence shows one individual was born in a much colder climate - similar to the Pyrenees Mountains to the south.
It's unclear whether this person migrated to the Le Tumulus des Sables region, or whether their whole skeleton, or single tooth, was brought back and buried there.
Archaeologists also found a jumble of metal, pottery and animal bones at the site, which made it difficult to identify the human remains and understand the occupation of the site.
"We found a lot of baby teeth, as well as teeth without full roots, which means the person died in childhood, while the tooth was still forming," Ms James said.
"We analysed the same tooth each time, to make sure we were looking at different individuals - but the actual number of people buried there could be much higher."
The research is published in the Journal of Archaeological Science: Reports.
Ms James would like to acknowledge the assistance of Professor Patrice Courtaud and his team from the Université de Bordeaux.
