Stonehenge may be the most famous example, but tens of thousands of other ancient sites featuring massive, curiously arranged rocks dot Europe. A new study suggests these megaliths weren’t created independently but instead can be traced back to a single hunter-gatherer culture that started nearly 7000 years ago in what is today the Brittany region of northwestern France. The findings also indicate societies at the time were better boaters than typically believed, spreading their culture by sea.

“This demonstrates absolutely that Brittany is the origin of the European megalithic phenomenon,” says Michael Parker Pearson, an archaeologist and Stonehenge specialist at University College London.