Yuichiro Kudo

Little is known about the spatiotemporal dynamics of gray wolves in the Pleistocene across low-latitude regions of Eurasia. In Japan, a small-bodied endemic subspecies of Japanese wolves existed and went extinct in the early 1900s. The fossil record indicates that a giant wolf, which reached 70 cm in body height, inhabited Japan during the Pleistocene, but its evolutionary relationship, if any, with the Japanese wolf remains uncertain. Here, to reveal the genetic origin of the Japanese wolf, we analyzed ancient DNA from remains (recovered in Japan) of one Pleistocene wolf that lived 35,000 years ago and one Holocene wolf from 5,000 years ago. The analysis of the mitochondrial DNA revealed that the Pleistocene wolf was not part of the Japanese wolf clade but rather an earlier-diverging lineage. The analysis of the nuclear DNA of the Holocene Japanese wolf revealed that it was an admixture of the Japanese Pleistocene wolf and continental wolf lineages. These findings suggest that the Japanese wolf originated via waves of colonization of multiple Pleistocene wolf populations at 57-35 and 37-14 ka, respectively, followed by interpopulation hybridization.

We reconstructed the palaeo-environmental changes during the Last Glacial Stage from fossil pollen and wood profiles and radiocarbon dates of the deposits along the Hanamuro River, Ibaraki Prefecture, eastern Japan. The fossil pollen and wood profiles indicated that, on the upland, 1) in ca. >50-43 ka, a cool temperate deciduous broad-leaved forest was distributed in a somewhat warm climate, 2) in ca. 38-35 ka, a mixed forest of cool-temperate deciduous broad-leaved trees and boreal conifers dominated in a cool climate, and 3) in ca. 35-17 ka, a boreal coniferous forest was distributed in a cold climate・On gentle slopes and valley floors, a swamp forest consisting of Alnus and Salix developed in ca. >50-24 ka. In ca. 24-17 ka, a grassland expanded on the peat land. Additionally, we investigated the palaeo-ecology of an extinct Hemiptelea mikii Minaki et al. It grew around this region until ca. 43-38 ka and seemed to have died out, due to the cold and dry conditions during the Last Glacial Maximum. It is highly possible that its habitat was influenced by the soil disturbance and the fluctuation of ground-water level.

Shimo-yakebe site is one of the most important wetland site from Middle to Final Jomon sub-period (ca. 5,300-2,800 cal BP) in the Kanto plain, central Japan. Total of 40 charred plant remains attached to the Jomon potteries had been excavated from varied valley. Charred plant remains on potsherds are ideal for investigating the cooking method of plant foods using pottery during the Jomon period. These charred plant remains are classified into five groups: scaly bulbs remains, fiber remains, fruits and seeds remains, woven remains, and unidentified macro fossil remains. AMS radiocarbon dating, carbon and nitrogen stable isotope analysis and C/N ratio analysis were conducted for 26 charred plant remains to make more refined chronology and to examine origin of these charred plant remains. In addition, radiocarbon dating for 5 seeds and fruits remains conducted. Radiocarbon dating showed that these plant remains attached to the pottery were placed ca. 5,300-2,500 cal BP of the Middle to Final Jomon sub-period. Especially, large majority of these plant remains are placed ca. 3,300-2,700 cal BP of the Final Jomon-sub-period. Carbon and nitrogen stable isotope analysis shows that δ13C values of the all of these plant remains were from -26.5 to -22.5 ‰ (ave. -24.9 ‰) and δ15N values were from 0.8 to 4.5 ‰ (ave. 2.3 ‰). These values are coincides with standard values of the C3 plants. Charred seeds of Leguminosae (Glycine sp. and Vigna angularis var. angularis type) were placed ca. 4,900 cal BP of the Middle Jomon, and charred fruits of Cannabis sativa placed ca. 3,500 cal BP of the Late Jomon sub-period. Charred seed of Glycine sp. found from the Shimo-yakebe site is the oldest record in the Jomon period at this moment.