Thousands of years ago, megaliths began to appear in Europe — standing stones, dolmens, stone circles. They vary from single stones to complexes like Stonehenge.

There are about 35,000 such monuments in Europe, many along the Atlantic coast of France and Spain, in England, Ireland, Scandinavia and throughout the Mediterranean. They attract both tourists and archaeologists, who have spent a century debating how the knowledge to build such monuments spread.

One idea suggested that this cultural change came from the Near East, and spread west along coastal routes, perhaps by a priestly caste. Later theories suggested techniques may have developed independently in different locales.

But a scientist who analyzed 2,410 radiocarbon dates of megaliths and their surroundings reported on Monday that the first such tombs appeared in France, about 6,500 years ago, and then spread along the Atlantic and Mediterranean coasts, as well as to England, Ireland and Scandinavia.

“It took me 10 years of my life for this research,” said the scientist, Bettina Schulz Paulsson, a prehistoric archaeologist at the University of Gothenburg in Sweden. She combed the literature in 11 languages, assessed the validity of the dating tests, and used a statistical method called Bayesian analysis to narrow the dates further.

She reported her findings in the journal PNAS, concluding that the building of megalithic graves appeared and spread along the coast of France, Spain and Portugal and the Mediterranean within a period of 200 to 300 years.