Japan's earliest settlers were fishers, hunters and gatherers who slogged over the land bridges from Korea to the west and Siberia to the north. It's also thought that seafaring migrants from Polynesia were part of the ethnic blend. By AD 300, the sun-worshipping Yamato kingdom had loosely unified the nation through conquest and alliance. Buddhism was introduced from China in the mid-6th century and soon became the state religion. Rivalry between Buddhism and Shintō, the traditional religion of Japan, was diffused by presenting Shintō deities as manifestations of Buddha.…