Early millet-based farming facilitated exponential population growth and spread discontinuously across eastern Asia.

The spatio-temporal distribution of archaeological sites in the Hokkaido region reveals hunter–gatherer population dynamics from the Upper Palaeolithic (>14,000 cal. yr BP) through the Neolithic/Jomon and Epi Jomom period (c. 14,000–1300 cal. yr BP) to the historic Ainu period (c. 700–100 cal. yr BP). It appears that most cultural transitions coincide with periods of climate and environmental change. However, this observation does not automatically mean causality and, therefore, other potential driving factors must be checked. The data support the hypothesis that Palaeolithic subsistence was (at least partly) based on terrestrial hunting. Paralleled by lateglacial climate amelioration, rising sea levels and a change in marine currents, this strategy shifted towards marine resources and plant exploitation at the beginning of the Jomon period. Along with continuous Holocene climate warming, Hokkaido’s Neolithic Jomon population increased culminating in the Middle Jomon period (5000–4000 cal. yr BP). Simultaneously, Jomon subsistence underwent a process of diversification and intensification in exploitation of food resources. This practice probably allowed the persistence of the Middle Jomon culture beyond the Holocene temperature optimum (around 5000 cal. yr BP). Thereafter, the population decreased until the end of the Jomon culture accompanied by a trend towards cooler climate conditions and a shift in subsistence towards a more narrow range of food resources with increased hunting and less plant food. Population re-increased during the Satsumon/Okhotsk culture periods (1500–700 cal. yr BP), which may be the result of Okhotsk immigration because of climate cooling in the regions north of Hokkaido and enhanced inner-Hokkaido trade (between Satsumon and Okhotsk) and trade with communities outside Hokkaido. During the Ainu period (c. 700–100 cal. yr BP), site, and possibly population numbers, re-decreased significantly and concentrated in eastern Hokkaido. Whether social and/or climatic factors brought about the Satsumon–Ainu cultural transition and the observed change in population pattern remains unresolved.

This paper discusses archaeobotanical remains of naked barley recovered from the Okhotsk cultural layers of the Hamanaka 2 archaeological site on Rebun Island, northern Japan. Calibrated ages (68% confidence interval) of the directly dated barley remains suggest that the crop was used at the site ca. 440–890 cal yr AD. Together with the finds from the Oumu site (north-eastern Hokkaido Island), the recovered seed assemblage marks the oldest well-documented evidence for the use of barley in the Hokkaido Region. The archaeobotanical data together with the results of a detailed pollen analysis of contemporaneous sediment layers from the bottom of nearby Lake Kushu point to low-level food production, including cultivation of barley and possible management of wild plants that complemented a wide range of foods derived from hunting, fishing, and gathering. This qualifies the people of the Okhotsk culture as one element of the long-term and spatially broader Holocene hunter–gatherer cultural complex (including also Jomon, Epi-Jomon, Satsumon, and Ainu cultures) of the Japanese archipelago, which may be placed somewhere between the traditionally accepted boundaries between foraging and agriculture. To our knowledge, the archaeobotanical assemblages from the Hokkaido Okhotsk culture sites highlight the north-eastern limit of prehistoric barley dispersal. Seed morphological characteristics identify two different barley phenotypes in the Hokkaido Region. One compact type (naked barley) associated with the Okhotsk culture and a less compact type (hulled barley) associated with Early–Middle Satsumon culture sites. This supports earlier suggestions that the “Satsumon type” barley was likely propagated by the expansion of the Yayoi culture via south-western Japan, while the “Okhotsk type” spread from the continental Russian Far East region, across the Sea of Japan. After the two phenotypes were independently introduced to Hokkaido, the boundary between both barley domains possibly existed ca. 600–1000 cal yr AD across the island region. Despite a large body of studies and numerous theoretical and conceptual debates, the question of how to differentiate between hunter–gatherer and farming economies persists reflecting the wide range of dynamic subsistence strategies used by humans through the Holocene. Our current study contributes to the ongoing discussion of this important issue.