From the Cover: Ancient DNA and multimethod dating confirm the late arrival of anatomically modern humans in southern China

The expansion of anatomically modern humans (AMHs) from Africa around 65,000 to 45,000 y ago (ca. 65 to 45 ka) led to the establishment of present-day non-African populations. Some paleoanthropologists have argued that fossil discoveries from Huanglong, Zhiren, Luna, and Fuyan caves in southern China indicate one or more prior dispersals, perhaps as early as ca. 120 ka. We investigated the age of the human remains from three of these localities and two additional early AMH sites (Yangjiapo and Sanyou caves, Hubei) by combining ancient DNA (aDNA) analysis with a multimethod geological dating strategy. Although U–Th dating of capping flowstones suggested they lie within the range ca. 168 to 70 ka, analyses of aDNA and direct AMS ¹⁴C dating on human teeth from Fuyan and Yangjiapo caves showed they derive from the Holocene. OSL dating of sediments and AMS ¹⁴C analysis of mammal teeth and charcoal also demonstrated major discrepancies from the flowstone ages; the difference between them being an order of magnitude or more at most of these localities. Our work highlights the surprisingly complex depositional history recorded at these subtropical caves which involved one or more episodes of erosion and redeposition or intrusion as recently as the late Holocene. In light of our findings, the first appearance datum for AMHs in southern China should probably lie within the timeframe set by molecular data of ca. 50 to 45 ka.

The fossil record suggests that Homo sapiens had evolved in Africa by 315,000 y ago (315 ka) (1), spread into West Asia before 177 ka (2), but disappeared and were seemingly replaced by Homo neanderthalensis until ca. 75 to 55 ka (3, 4). A second and final excursion from Africa by so-called anatomically modern humans (AMHs) occurred soon after and broadly coincides with the extinction of the last archaic hominins, ca. 40 to 30 ka (5, 6). This dispersal involved the ancestors of all present-day non-Africans and according to molecular data occurred ca. 65 to 45 ka (7, 8). Additional support for this “late dispersal” theory is provided by the geographical structure of contemporary DNA lineages with all non-Africans closely related to present-day and ancient eastern African populations (9, 10), as well as a clinal pattern of decreasing diversity from Africa to Eurasia, the signature of serial founder effect (10–12). Corroboration has also been provided by the estimated split time between western and eastern Eurasians of ca. 47 to 42 ka as determined by ancient DNA (aDNA) from the 46,880 to 43,210 cal y B.P. (calendar year before present, i.e., before AD1950) Ust’-Ishim femur (western Siberia, Russian Federation) and the 42,000 to 39,000 cal B.P. Tianyuan skeleton (Northeast China) (13–15). Finally, the upper age boundary for this dispersal is set by interbreeding between early AMHs and the Neanderthals estimated to have occurred ca. 65 to 47 ka and the ancestors of New Guineans with the Denisovans ca. 46 ka and again ca. 30 ka (13, 16–19).In contrast, some paleoanthropologists have suggested that AMHs settled mainland East Asia much earlier, within the period of ca. 120 to 70 ka, in accordance with the “early dispersal” theory. This model is based largely upon the dating of isolated human teeth recovered at Huanglong, Luna, and Fuyan caves and a partial mandible from Zhirendong in southern China (20–24). Yet several researchers have raised questions about these and other sites on the basis of uncertainties surrounding the identification of some of them as AMHs, relationships between human remains and dated materials, or limited information available about their depositional context and dating (25–27).Here, we describe the results of an investigation of the arrival time of AMHs in southern China at five apparent early AMH cave localities involving aDNA analyses of human teeth and the dating of flowstones, sediments, fossil remains, and charcoal. The five localities we studied are the following:

• 1)Huanglong cave, located about 25 km from the town of Yunxi, northern Hubei Province (Fig. 1). Excavations by the Hubei Provincial Institute of Cultural Relics and Archaeology during three field seasons from 2004 to 2006 provided a rich mammal record, comprising 91 taxa and representing a Middle to Late Pleistocene Ailuropoda-Stegodon fauna, stone artifacts, and seven AMH teeth dated indirectly with U–Th dating on thin flowstone formations ca. 101 to 81 ka (20).Open in a separate windowFig. 1.(A) Geographical location of Huanglong Cave (1), Luna Cave (2), Fuyan Cave (3), Yangjiapo Cave (4), and Sanyou Cave (5). (B) Human remains from three localities: Yangjiapo Cave (i), Sanyou Cave (ii), and Fuyan Cave (iii). b = buccal, d = distal, l = lingual, m = mesial, and o = occlusal).
• 2)Luna cave, situated in the karst mountains of the southeastern part of the Bubing basin, Guangxi Zhuang Autonomous Region (Fig. 1). A small sample of mammal fossils (Ailuropoda-Stegodon assemblage), stone artifacts, and two AMH teeth were recovered during excavations by the Natural History Museum of Guangxi Autonomous Region in 2004 and 2008. They have since been dated indirectly through U–Th dating of flowstone in the range ca. 127 to 70 ka (21).
• 3)Fuyan cave, located in Daoxian County, Hunan Province (Fig. 1). Excavations from 2011 to 2013 resulted in a large sample of mammal fossils (Ailuropoda-Stegodon faunal group) and 47 AMH teeth but no associated artifacts (22). They have been dated indirectly using U–Th dating of flowstone within the range ca. 120 to 80 ka (22). Two additional (in situ) AMH teeth, stratigraphically associated with the original finds, were recovered by us during field investigations at the site during early 2019.
• 4)Yangjiapo Cave is a large karstic chamber located in Jianshi County (Fig. 1). It was excavated during 2004 by the Hubei Provincial Institute of Cultural Relics and Archeology and yielded 11 AMH teeth found in association with the fragmentary bones of 80 species belonging to an Ailuropoda-Stegodon fauna, implying it should be of similar age to Huanglong, Luna, and Fuyan caves. No stone artifacts or other cultural remains were found.
• 5)Sanyou Cave is a small chamber within a limestone hill at the confluence of the Yangtze River and Xiling Gorge, close to Yichang city, Hubei Province (Fig. 1). A small excavation was undertaken in 1986 by the Yichang Museum and led to the recovery of a possible Late Pleistocene age partial AMH cranial vault (Fig. 1).