paragraph: Prehistory and Early Chronicles: As evidenced by bones, weapons, and pottery most recently uncovered by archeologists, the Asian equivalent of Neanderthal Man crossed a now-submerged land bridge from eastern Siberia to what is now Sakhalin Island and northern Japan some 100,000 years ago. These migrants, who later settled throughout the Japanese archipelago, were the ancestors of the present-day Ainu, whose Caucasoid facial and body hair distinguished them from subsequent immigrants from China, Manchuria, Korea, and perhaps the Malay Peninsula. It was the growth and military assertion of the newcomers that drove the "hairy people" (as they were labeled) back north to their present concentration in Hokkaido. The oldest Stone Age settlements to be discovered (10,000 b.c. ) are known as Jomon ("cord pattern"), after the style of their handmade pottery, which was among the earliest to be found anywhere in the world and of rich and imaginative design. Their inhabitants dwelled in sunken pits and lived from hunting, fishing, and the gathering of roots and nuts. It wasn't until the third century b.c. that techniques of rice cultivation (and wheel-made pottery) arrived from Korea, along with irrigation methods that are still in use today. The scarcity of flatlands suitable for cultivation made it possible for a small aristocratic elite to gain quick control of the food resources. This set the pattern of hierarchic rule that was to prevail right up to the last half of the 19th century (some would claim, in economic terms at least, that it still persists today). Although there are no reliable accounts of this period, third-century Chinese documents speak of a Japanese priestess-queen, Himiko, ruling over a land of law-abiding people who enjoyed alcohol and were divided into classes distinguished by tattoo marks. Five centuries later, Japan's own Kojiki and Nihon-shoki chronicles describe the creation of the imperial dynasty in the year 660 b.c. : the first emperor, Jimmu ("Divine Warrior") — great grandson of the Sun Goddess's grandson — embarked on an expedition of conquest from Kyushu along the Inland Sea coast to the Yamato plain of the Kinki region (near modern-day Nara). Plausible chronicling, laced with a dose of mythology, begins with the arrival of Korean scribes at the Japanese court around a.d. 400, at a time when Japan also had a military foothold in southern Korea. The state of Yamato, as early Japan was known, was organized into uji, or clusters of clans, together with subordinate guilds of farmers, fishermen, hunters, weavers, and potters, all subject to the dominant uji of the imperial family. 
question: When did techniques of rice cultivation arrive in Jomon from Korea?
answer: Third century B.C