At http://phys.org/print393494658.html … Japanese archaeologists have unearthed fish hooks on Okinawa dating from deep in the Late Glacial Maximum. It is know humans have been visiting the island of Okinawa for an estimated 50,000 years but this appears to be evidence of permanent settlement. They also seem to have eaten frogs, birds, small mammals, eels, as well as fish. People appear to have been living on Okinawa from 35,000 years ago – and the assumption made is that it was an island then as now and people arrived in boats.
See also https://heritageofjapan.wordpress.com/2016/09/18/archaeologists-find-wor… … Okinawa is situated roughly midway between Taiwan and Japan, a strategic stepping stone in migratory movement. How much of the continental shelf was above sea level at any point in the prehistoric past is an unknown. Looking at a map of the sea floor one can't be entirely sure Okinawa was always an island – but assuming it was it may have played a role in the movement of people from SE Asia northwards (as theorised by Stephen Oppenheimer). However, the Japanese don't necessarily see a link between the Jomon culture and the Indonesian region but rather, see Jomon origins in NE Asia – and they have genetic evidence to suggest so (but so too did Oppenheimer). The Jomon were great fishermen and spread their culture around the North Pacific rim, with a particular fancy for tuna. Fish hooks have been found on islands such as Timor, situated between what was Sunda Land and New Guinea/Australia, straddling the so called Wallace Line (and deep water).