Radiocarbon dating of cremated bodies excavated from Britain’s Stonehenge have solved part of the mystery surrounding the 5,000-year-old site: It was a burial ground for what might have been the country’s first royal dynasty.

The new dates indicate burials began at least 500 years before the first giant stones were erected at the site and continued after it was completed, British archaeologists said yesterday.

The pattern and relatively small number of the graves suggest all were members of a single family.

The findings provide the first substantive evidence that a line of kings ruled at least the lower portion of the British island during this early period, exerting enough power to mobilize the manpower necessary to move the stones from as far as 150 miles away and maintaining that power for at least five centuries, said archaeologist Mike Parker Pearson of the University of Sheffield, leader of the current excavations at the site.

“It was clearly a special place at that time,” he said. “One has to assume that anyone buried there had some good credentials.”

Parker Pearson presented the new data at a teleconference organized by the National Geographic Society. It also will appear in the June issue of National Geographic and in the television special “Stonehenge Decoded,” to be shown Sunday.

Stonehenge, on Salisbury Plain southwest of London, consists of concentric circles of giant stones — some weighing as much as 50 tons — surrounded by an earthen bank and a ditch.