Selection for Oil Content During Soybean Domestication Revealed by X-Ray Tomography of Ancient Beans.

When and under what circumstances domestication related traits evolved in soybean (Glycine max) is not well understood. Seed size has been a focus of archaeological attention because increased soybean seed weight/size is a trait that distinguishes most modern soybeans from their ancestors; however, archaeological seed size analysis has had limited success. Modern domesticated soybean has a significantly higher oil content than its wild counterpart so oil content is potentially a source of new insight into soybean domestication. We investigated soybean oil content using X-ray computed tomography (CT; specifically, synchrotron radiation X-ray CT or SRX-CT) of charred, archaeological soybean seeds. CT identified holes in the specimens that are associated with oil content. A high oil content facilitates the development of small holes, whereas a high protein content results in larger holes. The volume of small holes increased slowly from 7,500 to 4,000 cal B.P. We infer that human selection for higher oil content began as early as 7,500 cal B.P. and that high oil content cultivars were well established by 4,000 cal B.P.

Rice Domestication Revealed by Reduced Shattering of Archaeological rice from the Lower Yangtze valley.

Plant remains dating to between 9000 and 8400 BP from a probable ditch structure at the Huxi site include the oldest rice (Oryza sativa) spikelet bases and associated plant remains recovered in China. The remains document an early stage of rice domestication and the ecological setting in which early cultivation was taking place. The rice spikelet bases from Huxi include wild (shattering), intermediate, and domesticated (non-shattering) forms. The relative frequency of intermediate and non-shattering spikelet bases indicates that selection for, at the very least, non-shattering rice was underway at Huxi. The rice also has characteristics of japonica rice (Oryza sativa subsp. japonica), helping to clarify the emergence of a significant lineage of the crop. Seeds, phytoliths and their context provide evidence of increasing anthropogenesis and cultivation during the occupation. Rice spikelet bases from Kuahuqiao (8000-7700 BP), Tianluoshan (7000-6500 BP), Majiabang (6300-6000 BP), and Liangzhu (5300-4300 BP) sites indicate that rice underwent continuing selection for reduced shattering and japonica rice characteristics, confirming a prolonged domestication process for rice.

Archaeological evidence for peach (Prunus persica) cultivation and domestication in China.

The cultivated/domesticated peach (Prunus persica var. persica; Rosaceae, subgenus Amygdalus; synonym: Amygdalus persica) originated in China, but its wild ancestor, as well as where, when, and under what circumstances the peach was domesticated, is poorly known. Five populations of archaeological peach stones recovered from Zhejiang Province, China, document peach use and evolution beginning ca. 8000 BP. The majority of the archaeological sites from which the earliest peach stones have been recovered are from the Yangzi River valley, indicating that this is where early selection for favorable peach varieties likely took place. Furthermore, peach stone morphology through time is consistent with the hypothesis that an unknown wild P. persica was the ancestor of the cultivated peach. The oldest archaeological peach stones are from the Kuahuqiao (8000-7000 BP) and Tianluoshan (7000-6500 BP) sites and both stone samples segregate into two size groups, suggesting early selection of preferred types. The first peach stones in China most similar to modern cultivated forms are from the Liangzhu culture (ca. 5300 to 4300 BP), where the peach stones are significantly larger and more compressed than earlier stones. Similar peach stones are reported from Japan much earlier (6700-6400 BP). This large, compressed-stone peach was introduced to Japan and indicates a yet unidentified source population in China that was similar to the Liangzhu culture peach. This study proposes that the lower Yangzi River valley is a region, if not the region, of early peach selection and domestication and that the process began at least 7500 years ago.

Archaeological soybean (Glycine max) in East Asia: does size matter?

The recently acquired archaeological record for soybean from Japan, China and Korea is shedding light on the context in which this important economic plant became associated with people and was domesticated. This paper examines archaeological (charred) soybean seed size variation to determine what insight can be gained from a comprehensive comparison of 949 specimens from 22 sites. Seed length alone appears to represent seed size change through time, although the length × width × thickness product has the potential to provide better size change resolution. A widespread early association of small seeded soybean is as old as 9000-8600 cal BP in northern China and 7000 cal BP in Japan. Direct AMS radiocarbon dates on charred soybean seeds indicate selection resulted in large seed sizes in Japan by 5000 cal BP (Middle Jomon) and in Korea by 3000 cal BP (Early Mumun). Soybean seeds recovered in China from the Shang through Han periods are similar in length to the large Korean and Japanese specimens, but the overall size of the large Middle and Late Jomon, Early Mumun through Three Kingdom seeds is significantly larger than any of the Chinese specimens. The archaeological record appears to disconfirm the hypothesis of a single domestication of soybean and supports the view informed by recent phyologenetic research that soybean was domesticated in several locations in East Asia.

Plants and people from the Early Neolithic to Shang periods in North China.

An assemblage of charred plant remains collected from 26 sites in the Yiluo valley of North China as part of an archaeological survey spans the period from the sixth millennium to 1300 calibrated calendrical years (cal) B.C. The plant remains document a long sequence of crops, weeds, and other plants in the country. The results also demonstrate the effectiveness of sediment sampling as part of an archaeological survey. Ten accelerator mass spectrometer (AMS) radiocarbon dates on crop remains inform an assessment of the sequence of agricultural development in the region. Foxtail millet (Setaria italica subsp. italica) was grown during the Early Neolithic period and was the principal crop for at least four millennia. Broomcorn millet (Panicum miliaceum) was significantly less important throughout the sequence. Rice (Oryza sativa) was introduced by 3000 cal B.C. but apparently was not an important local crop. Wheat became a significant crop between 1600 and 1300 cal B.C. The weed flora diversified through time and were dominated by annual grasses, some of which were probably fodder for domesticated animals. The North China farming tradition that emphasized dry crops (millets, wheat, and legumes) with some rice appears to have been established at the latest by the Early Shang (Erligang; 1600-1300 B.C.) period.