Japonic speakers were also present on the southern and central "Korean Peninsula". These "Peninsular Japonic agriculturalists" were later replaced/assimilated by Koreanic-speakers (from southern Manchuria) likely causing the Yayoi migration and expansion within the Japanese archipelago. Whitman (2012) suggests that the Yayoi agriculturalists are not related to the proto-Koreans but that they were present on the Korean peninsula during the Mumun pottery period. According to him, Japonic arrived in the Korean peninsula around 1500 BC and was brought to the Japanese archipelago by the Yayoi agriculturalists at around 950 BC, during the late Jōmon period. The language family associated with both Mumun and Yayoi culture is Japonic. Koreanic arrived later from Manchuria to the Korean peninsula at around 300 BC and coexist with the descendants of the Japonic Mumun cultivators (or assimilated them). Both had influence on each other and a later founder effect diminished the internal variety of both language families.