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.