Location maps of the study region, Hamanaka 2, the RK12 coring site and other archaeobotanical records discussed in the text.

<p>Map compilation showing (A) the location of the study region in the northwest Pacific region; (B) the southern Primor’e Region (Russia); (C) the Hokkaido and northern Tohoku regions; (D) Rebun Island; and (E) the northern part of Rebun with Lake Kushu (white cross indicates location of the RK12 coring site) and the Hamanaka 2 archaeological site. Dots illustrate the locations of Okhotsk culture (yellow), Satsumon culture (green), Heian period (blue), and the RFE Iron Age–Eastern Xia State (red) barley records used for seed morphological comparison (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.s003" target="_blank">S3 Table</a> for site names and further details). Red circles in (C) show the location of the 194 Okhotsk culture sites listed in the Hokkaido archaeological site database (<a href="http://www2.wagamachi-guide.com/hokkai_bunka/" target="_blank">http://www2.wagamachi-guide.com/hokkai_bunka/</a>). The dashed line marks the proposed boundary of where the two barley morphotypes dominate. Bathymetry of Lake Kushu (0.5 m isolines) is based on survey data provided by T. Haraguchi (Osaka City University). Topographic maps are based on data from the elevation Shuttle Radar Topography Mission (SRTM) V4.1 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.ref024" target="_blank">24</a>]. Isolines for the terrestrial area in (E) are drawn from a topographic map [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.ref025" target="_blank">25</a>].</p

Sample-specific total counts of selected macrobotanical remains and floated litres from the Okhotsk culture layer units of Hamanaka 2.

<p>Sample-specific total counts of selected macrobotanical remains and floated litres from the Okhotsk culture layer units of Hamanaka 2.</p

Simplified pollen diagram representing the section dating between 50 cal yr BC and 1540 cal yr AD (67 pollen spectra) of the sediment core RK12 from Lake Kushu, Rebun Island.

<p>Chronology of prehistoric cultures in northern Hokkaido comprises Epi-Jomon (EJ; ca. 100 cal yr BC–500 cal yr AD including the Susuya tradition ca. 100–500 cal yr AD), Okhotsk culture (OK; ca. 500–950 cal yr AD), and Proto-Ainu/Formative Ainu (PA; ca. 950–1600 cal yr AD) (according to [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.ref026" target="_blank">26</a>] and [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.ref027" target="_blank">27</a>]).</p

Box-plots showing the L/W distribution of barley seeds from the Hamanaka 2 Okhotsk culture layers (this study) and of selected records from other regions.

<p>The boxes delineate the 25–75% quartiles (regular font) with the median (italic font) shown as an inset horizontal line. The whiskers (inner fence) are defined as the array from top/bottom of the box to the largest/smallest data point less than 1.5 times the box height from the box. Data points inside and outside (outliers) the whiskers are marked by grey and blue dots, respectively. Dotted horizontal lines indicate arithmetic means of Satsumon barley populations. Sample size (if know) and site numbers used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.g001" target="_blank">Fig 1</a> are provided. Ages are given in calendar years.</p

Radiocarbon dates and calibrated ages on carbonised barley seeds from the Okhotsk culture layers of the Hamanaka 2 site, Rebun Island, Hokkaido.

<p>Radiocarbon dates and calibrated ages on carbonised barley seeds from the Okhotsk culture layers of the Hamanaka 2 site, Rebun Island, Hokkaido.</p

Summary of the barley assemblage in the Hamanaka 2, Rebun Island, northern Japan.

<p>Absolute and relative amounts of naked barley <i>Hordeum vulgare</i> var. <i>nudum</i>) seeds (incl. <i>Hordeum</i>/<i>Triticum</i> type) and identified pottery types per cultural layer. Given age ranges are based on radiocarbon dates of barley seeds (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0174397#pone.0174397.t002" target="_blank">Table 2</a>) with black and white bars indicating 68% and 95% confidence interval, respectively.</p

A selection of compact naked barley grains from Okhotsk culture layers of the Hamanaka 2 site, Rebun Island, northern Japan.

<p>Depicted grains are representative of the barley-bearing cultural layers (IIIa–e) covering the time period ca. 430–960 cal yr AD. Each of the six specimens is shown in ventral (a), dorsal (b), and lateral (c) views.</p

Hamanaka 2 cultural layers associated with the Okhotsk culture and available flotation samples.

<p>Hamanaka 2 cultural layers associated with the Okhotsk culture and available flotation samples.</p