After World War II, Kotondo Hasebe and Hisashi Suzuki claimed that the origin of Japanese people was not newcomers in the Yayoi period (300 BCE – 300 CE) but the people in the Jōmon period. However, Kazuro Hanihara announced a new racial admixture theory in 1984 and a "dual structure model" in 1991. According to Hanihara, modern Japanese lineages began with Jōmon people, who moved into the Japanese archipelago during Paleolithic times, followed by a second wave of immigration, from East Asia to Japan during the Yayoi period (300 BC). Following a population expansion in Neolithic times, these newcomers then found their way to the Japanese archipelago sometime during the Yayoi period. As a result, replacement of the hunter gatherers was common in the island regions of Kyūshū, Shikoku, and southern Honshū, but did not prevail in the outlying islands of Okinawa and Hokkaidō, and the Ryukyuan and Ainu people show mixed characteristics. Mark J. Hudson claims that the main ethnic image of Japanese people was biologically and linguistically formed from 400 BCE to 1,200 CE. Currently, the most well-regarded theory is that present-day Japanese people formed from both the Yayoi rice-agriculturalists and the various Jōmon period ethnicities.