The origin of Yayoi culture and the Yayoi people has long been debated. The earliest archaeological sites are Itazuke or Nabata in the northern part of Kyūshū. Contacts between fishing communities on this coast and the southern coast of Korea date from the Jōmon period, as witnessed by the exchange of trade items such as fishhooks and obsidian. During the Yayoi period, cultural features from Korea and China arrived in this area at various times over several centuries, and later spread to the south and east. This was a period of mixture between immigrants and the indigenous population, and between new cultural influences and existing practices.