A prehistoric burial mound in southwest France was used and re-used by locals for more than two millennia, according to an analysis of bones and teeth from the site.

The Le Tumulus des Sables site is in the small town of Saint-Laurent-Médoc, 40 kilometres north-west of Bordeaux. It was discovered by accident in 2006 when curious toddlers rummaging around in their kindergarten playground pulled human remains from the soil.

Archaeologists were brought in, and from the ancient jumble of pottery and bones they found, the site was quickly identified as a burial mound, an area of raised earth atop a gravesite.

Much of the pottery in the mound was in the distinctive Bell Beaker style: squat cups that look like upturned bells. Bell beakers have been found across Europe – from Spain and the United Kingdom through to Germany and central Europe – and often in graves.

“It’s one of first cultures which spreads out all across Europe,” says archeological scientist Hannah James from the Australian National University.

In France, the Bell Beaker period lasted from around 2500 to 1800 BCE.

The remains of at least 20 adults and 10 children – none as complete skeletons – have been exhumed from Le Tumulus des Sables, and all were initially assumed to be from this time. Indeed, a previous study dated two bone fragments to within this period.

But ceramics from as far back as the middle Neolithic – around 5500 BCE – and as recently as the Iron Age – around 1000 BCE – have also been found at the site.

With everything in the mound jumbled together, working out which artefacts belong to which individuals has been impossible. “It’s all quite mixed up,” says James.

In the current study, published in the Journal of Archaeological Science Reports, James and colleagues date a further eight individuals, using teeth from seven adults and one child.

[Six of the teeth were from the Bell Beaker period, but one was much older – dating to between 3650 and 3522 BCE – and one much younger – from 1277 to 1121 BCE – suggesting the mound was used for more than 2000 years.

It’s not known how the Bell Beaker culture spread through Europe. Possible drivers are migration, trade or the transmission of technological know-how. The burial mound findings add to the picture, but do not necessarily make it clearer.

By analysing isotopes of strontium, carbon, nitrogen and oxygen in teeth, James and her colleagues were able to paint a picture of the childhood diet of the individuals buried at the site and where they grew up.

Carbon and nitrogen isotope ratios in eight teeth point to a terrestrial diet lacking in seafood, despite the site being within walking distance of the Gironde Estuary and the Atlantic Ocean.

Teeth from 18 adults and seven children were analysed for strontium isotopes, and oxygen isotope analysis was conducted on 15 of these – 14 adults and one child.

All bar one adult appeared to have grown up locally, as the signature of strontium and oxygen values for the teeth matched those from local soil and animal samples.

This suggests that at Saint-Laurent-Médoc the Bell Beaker people were less mobile than in other Bell Beaker sites. Places in Germany, Austria, the Czech Republic and Hungary have recorded almost two-thirds of individuals from outside the local area.