Human remains from Zhirendong, South China, and modern human emergence in East Asia

Abstract

The 2007 discovery of fragmentary human remains (two molars and an anterior mandible) at Zhirendong (Zhiren Cave) in South China provides insight in the processes involved in the establishment of modern humans in eastern Eurasia. The human remains are securely dated by U-series on overlying flowstones and a rich associated faunal sample to the initial Late Pleistocene, >100 kya. As such, they are the oldest modern human fossils in East Asia and predate by >60,000 y the oldest previously known modern human remains in the region. The Zhiren 3 mandible in particular presents derived modern human anterior symphyseal morphology, with a projecting tuber symphyseos, distinct mental fossae, modest lateral tubercles, and a vertical symphysis; it is separate from any known late archaic human mandible. However, it also exhibits a lingual symphyseal morphology and corpus robustness that place it close to later Pleistocene archaic humans. The age and morphology of the Zhiren Cave human remains support a modern human emergence scenario for East Asia involving dispersal with assimilation or populational continuity with gene flow. It also places the Late Pleistocene Asian emergence of modern humans in a pre-Upper Paleolithic context and raises issues concerning the long-term Late Pleistocene coexistence of late archaic and early modern humans across Eurasia.

Archaic human ancestry in East Asia

“…The lack of evidence of Denisova ancestry in other Eurasian populations indicates that this genetic material was introduced into the ancestral population of Southeast Asians after the time of divergence from Europeans, a date that has been estimated to 23-45 kya (58, 59) but could also have occurred considerably earlier (27,28,30). The apparent absence of Denisova ancestry in Native Americans in our study could be influenced by the biased affinity to the Neandertal genome that is expected because of ascertainment bias and genetic drift, but analyses of unascertained low-coverage shotgun sequence data from a single Native American individual resulted in a similar conclusion (24).…”

“…Similarly, the suggestion of archaic Asian ancestry in Oceania is partly supported by some morphological interpretations of the fossil record (4,26). However, similar, and arguably more suggestive (4,6), morphological evidence for admixture with archaic populations has been found in early modern human remains from East Asia (4,6,(27)(28)(29)(30) and Europe (4,(31)(32)(33). Thus, it is possible that additional genomic signs of archaic admixture remain undetected because of inadequate sampling of ancient and/or contemporary human genetic variation (23)(24)(25).…”

Genomic and cranial phenotype data support multiple modern human dispersals from Africa and a southern route into Asia

“…Occupation of Australia is documented by the human paleontological record at ∼50 ka and in continental Southeast Asia at a maximum date of ∼63 ka (8,35). Specimens before this time period are fragmentary and taxonomically ambiguous but have, in some cases, been claimed to represent anatomically modern humans (6,7,(35)(36)(37). The MDI-MP model tested here suggests that whereas Southeast Asia may have been populated by modern humans, replacement of these descendants from subsequent migrants may obscure a southern route biological signal in extant populations of that region (6).…”

Late Pleistocene adult mortality patterns and modern human establishment

“…The ages of the majority of the specimens were based on assessments of occlusal wear, in which all of the postcanine teeth of the individuals in the younger age category preserved the majority of their occlusal enamel [Smith (62) categories [1][2][3][4][5]. When possible, these assessments were combined with skeletal indicators, including pubic symphysis and auricular surface metamorphosis, femoral diaphyseal histomorphology, costal cartilage ossification, proximal femoral trabecular changes, and sacral body ventral ossification, but not suture closure.…”