Dr. Yan Wu’s phytolith research in China

Dr. Yan Wu’s phytolith research in China

Professor Wu Yan, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences

The main academic contributions achieved are reflected in the following three aspects:

1. Breakthroughs in paleoanimal diet and paleoecology research

1.1 Phytolith evidence reveals the origin of angiosperm leaf-eating habits among ancient Cretaceous birds

Recently, a study published in Nature Communications focused on the feeding habits of an ancient bird called Jeholornis from China’s Early Cretaceous Jehol Biota. Jeholornis is located in a relatively basal position in the avian evolutionary tree. The study of its diet has important significance for early avian ecological origin radiation. The analysis of a complete fossil digestive tract material of Jeholornis found enriched ancient phytoliths. It was confirmed that the gizzard contents of Jeholornis retained evidence of phytoliths from magnolia leaves. This discovery precisely identified the plant type of known early herbivorous birds to the leaves of magnolia plants. At the same time, it provides new evidence for transforming the arboreal ecological position of the common herbivorous nature of birds. This is a significant breakthrough in applying phytolith analysis methods to studying Mesozoic vertebrate fossils. It provides important means and approaches for further expanding the research on the coevolution of vertebrates and the environment.

1.2 Dinosaur diet research

Poaceae is the most important category of monocotyledonous angiosperms, including the most important crops of mankind, such as rice, wheat, and corn. The origin of Poaceae has always been a major scientific issue in biological evolution research. After nearly four years of efforts, this study successfully extracted plant epidermis and phytoliths for the first time from a special structure preserved around the teeth of a basal hadrosauroid dinosaur (Equijubus normani) from the late Early Cretaceous period more than 100 million years ago. Through in-depth analysis and comparative research, it is revealed that these epidermal cells containing short cell pairs and dumbbell-shaped phytoliths belong to the most basal group of Poaceae, greatly advancing the earliest fossil record of Poaceae to more than 100 million years ago in the Early Cretaceous, which is an important progress in the study of the origin of Poaceae plants.

1.3 Coevolution of diet and plants of large mammals in the Neogene

The grassland ecosystem dominated by Poaceae expanded significantly in the Neogene, promoting primary adaptive evolutionary responses of various herbivorous mammals. Proboscideans are important components of terrestrial faunas. The study of their diet is a critical issue in biological evolution and paleoenvironmental research. Through three years of in-depth research, it was found for the first time that G. steinheimense, the direct ancestor of elephants in the early Middle Miocene about 16 million years ago, is an herbivorous diet type. This discovery breaks the traditional view of the diet of gomphotheres and reconstructs a new understanding of the diet of gomphotheres.
Combined with the results of tooth microwear, isotope, and pollen analysis of gomphotheres, we speculate that when the initial grassland ecology appeared, G. steinheimense chose to feed on less comfortable grasses. Its molar morphology also gradually changed and finally fully adapted to feeding on grasses, thus surviving until today. Therefore, this study provides new evidence that animal behaviour evolution leads to morphological evolution.

2. Coevolution research of ancient human diet and environment

2.1 Diet of the earliest modern humans in East Asia

Diet evolution is an important part of human evolution and is also vital evidence for discussing human physical and behavioural evolution. The Fuyan Cave site in Daoxian, Hunan Province, discovered the earliest modern humans in East Asia, dating back 80,000 to 120,000 years. Through the analysis of the dental calculus of these modern humans, it was found that ancient humans fed on carbohydrates such as acorns, tubers, and rhizomes, filling the gap in the plant-based diet of early modern humans in East Asia and providing key evidence for the evolution of modern human diet and environmental adaptability.

2.2 Obtaining the plant utilisation of ancient humans in Guangxi in the last 30,000 years

The last 30,000 years have been a crucial period of global climate change in the Late Pleistocene, which has had a broad and profound impact on humans. The identification and utilisation of plants are signs of the progress of human behavioural ability. Guangxi is one of the famous fossil sites of ancient humans and a key area for the emergence and evolution of modern humans. However, plant utilisation types and methods in this area have been relatively less studied.
The Yahuaidong site is located in Long’an County, Guangxi, and contains cultural remains from the Paleolithic and Neolithic periods. This site discovered extremely rare complete human skull fossils in China. Using AMS 14C dating, combined with the relics and artefacts of the site, a chronological framework for the research site is established. Through phytolith analysis, supplemented by pollen information, ancient human plant resource information is obtained. The study found that ancient humans used different plant species in different periods. In addition, the unique stone tool assemblage at the Yahuaidong site is similar to that of North China rather than South China, suggesting the possibility that due to climate cooling, ancient humans in the north migrated south and brought their accustomed tools and technologies.

3. Origin and spread research of rice cultivation

3.1 Obtaining new evidence for the origin of rice cultivation in the lower reaches of the Yangtze River 10,000 years ago

The origin of rice farming is one of the most critical events in human civilization. Its main research content involves rice domestication’s starting time, location, and motivation. The early Neolithic sites in southern China are unfavorable for preserving macro remains of rice and are challenging to become a reliable basis for discussing this important scientific issue. Based on the phytolith analysis of the Shangshan and Hehuashan sites, we obtained new evidence for the origin of rice farming in the lower reaches of the Yangtze River around 10,000 years ago. In the raw soil layer of the Hehuashan site of the Shangshan culture, phytoliths of wild-type rice were found. This fact implies that wild rice grew at the location of this site before human activities in the early Holocene. Combined with the relevant archaeological discoveries and research of the Shangshan culture, it is proved that the Qiantang River Basin is not only the birthplace of the Neolithic culture in the Zhejiang region but also may be the cradle of Chinese rice farming agriculture. This result was published in “Journal of Archaeological Science” in 2014 and in “Archaeological and Anthropological Sciences” in 2019.

3.2 Obtaining new evidence for the spread of rice cultivation and the spread of millet
We used phytolith analysis combined with carbonized plant remains to discuss the cultivation and utilization of rice at the Dongyang site in Shaanxi Province. We also tried to analyse the motivation and dissemination process for the appearance of rice in the Guanzhong area. The research shows that the rice remains at the Dongyang site, which is currently the earliest directly dated rice in the Guanzhong area, indicating that rice was introduced into the Guanzhong area at least 5,800 years ago. This study has refreshed the record of the earliest rice remains in China’s northern semi-arid and semi-humid regions and provided basic data for further understanding the origin and dissemination of rice farming. Through the study of prehistoric rice remains in the Lingnan region, the earliest directly dated macro remains of rice in the Pearl River Delta region (4,526-4,417 cal. a B.P.) were found at the Chaling site in Guangdong. This study has broken the inherent concept of the prehistoric fishing and hunting and gathering economic structure model in the Pearl River Delta region and provided new clues for further understanding the dissemination of rice in the Lingnan region.  Our analyses of macro botanical remains and phytoliths formed the basis for reconstructing the subsistence economy of ancient humans at the Jingshuidun site from the late Neolithic to early historic times. Domesticated rice macro botanical remains and phytoliths are present in layers at the Jingshuidun site dated to 4,874–4,820 cal. a B.P. (middle-late Liangzhu Period) and 2667–2568 cal. yr B.P. (late Western Zhou Dynasty to the early Spring and Autumn Period). Moreover, macrobotanical remains and phytoliths from the site document the earliest remains of foxtail millet (Setaria italica) in southern Anhui Province from a layer dating to the late Western Zhou Dynasty and the early Spring and Autumn Period (2,667–2,568 cal. a B.P.). These results suggest that the people occupying the Jingshuidun site used single rice farming as far back as 4874–4820 cal. a B.P. and they began to plant millet by at least 2,667–2,568 cal. a B.P., documenting the spread of millet agriculture to the southern area by that time.

Selected peer-reviewed publications

Wu Y,Ge Y,Hu H,Stidham T A,Li Z*,Bailleul A M;Zhou Z 2023. Intra-gastric phytoliths provide evidence for folivory in basal avialans of the Early Cretaceous Jehol Biota. Nature Communications [J], 14: 4558.
Wu Y*,Tao D,Wu X,Liu W;Cai Y 2022. Diet of the earliest modern humans in East Asia. Frontiers in Plant Science [J], 13: 989308.
Wu Y*,Xie G,Mao* L,Zhao Z;Belmaker M 2020. Phytolith evidence for human-plant subsistence in Yahuai Cave (Guangxi, South China) over the past 30000 years. Science China Earth Science [J]. 63: 1745-1757.
Wu Y*,Li Z*,Stidham T A;Foong S Y 2023. Phytolith evidence reveals the origin of angiosperm leaf eating habits among ancient Cretaceous birds. The Innovation [J], 4.
Wang J,Chen X,Zhang G,Zhang G;Wu Y *2022. The history of agriculture in the mountainous areas of the lower Yangtze River since the late Neolithic. Frontiers of Earth Science [J], 16: 809-818.
Qiu Z,Jiang L,Wang C,Hill D V;Wu Y* 2019. New evidence for rice cultivation from the Early Neolithic Hehuashan site. Archaeological and Anthropological Sciences [J], 11: 1259-1272.
Wu Y,You H-L*;Li X-Q 2018. Dinosaur-associated Poaceae epidermis and phytoliths from the Early Cretaceous of China. National Science Review [J], 5: 721-727.
Wu Y,Deng T,Hu Y,Ma J,Zhou X,Mao L,Zhang H,Ye J;Wang S-Q* 2018. A grazing Gomphotherium in Middle Miocene Central Asia, 10 million years prior to the origin of the Elephantidae. Scientific Reports [J], 8: 7640.
Wu Y*,Guo X,Wang W,Chen X,Zhao Z,Xia X;Yang Y 2017. Red pigments and Boraginaceae leaves in mortuary ritual of late Neolithic China: A case study of Shengedaliang site. Microscopy Research and Technique [J], 80: 231-238.
Wu Y*,Mao L,Wang C,Zhang J;Zhao Z 2016. Phytolith evidence suggests early domesticated rice since 5600 cal a BP on Hainan Island of South China. Quaternary international [J], 426: 120-125.
Wu Y*,Jiang L,Zheng Y,Wang C;Zhao Z* 2014. Morphological trend analysis of rice phytolith during the early Neolithic in the Lower Yangtze. Journal of archaeological science [J], 49: 326-331.
Wu Y*,Yang Y*,Xiao T,Gu Z,Hill D V;Wang C 2014. Characterization of silica distribution in rice husk using Synchrotron Radiation µCT and its implications for archaeological interpretation. Microscopy Research and Technique [J], 77: 785-789.
Wu Y*,Yang Y,Wang H;Wang C 2014. The effects of chemical composition and distribution on the preservation of phytolith morphology. Applied Physics A [J], 114: 503-507.
Wu Y*,Wang C;Hill D V 2012. The transformation of phytolith morphology as the result of their exposure to high temperature. Microscopy Research and Technique [J], 75: 852-855.
Wu Y,Wang C* 2011. EDF phytolith analysis from Heying site, southeast China, Shang‐Zhou dynasties. Microscopy Research and Technique [J], 74: 1062-1068.
Wang C* 2009. Extended Depth of Focus for Phytolith Analysis. Journal of Archaeological Science [J], 36(10):2253-2257.
Tao D, Wu Y,* Zhizhong Guo, Hill D V, Wang C 2011. Starch grain analysis for groundstone tools from Neolithic Baiyinchanghan site: implications for their function in Northeast China,Journal of Archaeological Science [J],38(12):3577-3583.
Sun X, Wu Y*, Wang C, Hill D V 2011.Comparing dry ashing and wet oxidation methods. The case of the rice husk (Oryza sativa L.), Microscopy Research and Technique [J],75(9):1272-1276.

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