Bronze goods and bronze-making techniques from the Asian mainland reached the Japanese archipelago as early as the 3rd century BC. It is believed that bronze and, later, iron implements and weapons were introduced to Japan near the end of this time (and well into the early Yamato period). Archaeological findings suggest that bronze and iron weapons were not used for war until later, starting at the beginning of the Yamato period, as the metal weapons found with human remains do not show wear consistent with use as weapons. The transition from the Jōmon to Yayoi, and later to the Yamato period, is likely to have been characterized by violent struggle as the natives were displaced and assimilated by the invaders with their vastly superior military technology. The most well-regarded theory is that present-day Yamato Japanese are descendants of both the Indigenous Jōmon people and the immigrant Yayoi people.