The Xujiayao site is located on the west bank of the Liyigou River, 1 km from Xujiayao Village, Gucheng District, Shanxi Province. Discovered in 1974, excavations were conducted in 1976, 1977 and 1979. The 27 hominid fossils recovered from Xujiayao include 12 pieces of parietal, with parietals 6 and 10 reasonably complete, two large occipital fragments, most of a temporal bone and part of the right maxilla from a 6-7 year old child. These were originally described by Jia et al. (1979) and Wu Mo Lin (1980), see below. A detailed description in English can be found in Wu and Poirier (1995) who assign the Xujiayao remains to archaic Homo sapiens.
The late Wu Mo-Lin who was responsible for describing the Xujiajo hominin fossils in 1980.
The Xujiayao locality contained a large quantity of vertebrate fossils (~5000) (Li et al 2017; Hong et al 2017), all of which were fragmentary like the hominin remains. The clean and uneroded fracture surfaces on many bones indicate that they were recently broken. Perhaps the site was exposed by mechanical excavation, which brought bones and artifacts (>30,000) to the surface. Uranium series dating of rhinoceros teeth obtained a date of 104,000-125,000 years BP (Chen et al., 1984; Chen et al., 1982). Hong et al (2017) combined ESR and high resolution magnetostratigraphy indicated a much earlier date of 260-370 ka. However, I think that this much earlier date is not consistent with the anatomy of the hominin dental and skeletal remains. These recent ESR dates are also in marked contrast to the preliminary optically stimulated luminesence (OSL) dates of 60-69 ka reported by Wu and Trinkaus (2012). Unfortunately, the precise relationship of the dates to the hominin fossils is unclear, particulary when fossil fragmentation suggests some degree of postdepositional disturbance at the site. A large quantity of stone artifacts were also recovered from Xujiayao and these have been discussed by Jia et al. (1979) and Wu et al. (1989). Large tools are rare while scrapers are relatively common (see Hong et al. 2017 for details). A number of bone and antler tools have been reported. I have no idea which date is a better indicator of the age of the hominin skeletal remains and artifacts, perhaps none of them are useful.
The infant left maxillary fragment (below) consists primarily of the alveolar portion and three recently erupted permanent teeth. Teeth consist of a partially erupted central incisor, a canine, root of a deciduous second molar and first permanent molar. Both the central incisor and canine are distinguished by marked shovelling, with tooth and palate dimensions suggesting that the maxilla was from a male infant. Occipital n. 7 consists of a complete occipital plane and part of the nuchal region. The occipital torus is broadest centrally and narrows laterally. There is minimal angualtion of the nuchal and occipital planes when viewed laterally. Occipital n. 15 is less complete and includes the left half and part of the right squama. Torus shape is similar to n. 7. Bone thickness in both occipitals is relatively great by modern East Asian standards (Brown 1987). Parietal n. 10 is complete except for its anterior part. The bone in this parietal is extremely dense and thickened. The parietal tuberosity is not prominent and parietal curvature suggests that this individual had maximum bi-parietal breadth located inferiorally. The posterior extension of the temporal line forms a pronounced crest. Bone thickness and suture development in parietal n. 6 suggests that it is from a juvenile. This parietal has a prominent tuberosity. Some dimensions of the Xujiayao bones and teeth are provided below. Most recently Wu et al. (2012) have described an enlarged parietal foramen in Xujiayao 11 parietals and Wu and Trinkaus have completed a new comparative description of the Xujiayao adult mandibular ramus.
Most recently, there has been some debate about the chronological age of the Xujiayao juvenile (PA1480) and the accuracy of the methods used to estimate it. Chronological age can be based on the development stage and eruption of individual teeth, or a combination of the estimates for the complete dentition. The age and development of this infant are of interest as there is research suggesting that some Plio-Pleistocene hominins had an increased rate of growth and development in comparison with modern humans. Xing et al (2019) conclude that Xujiayao was the first archaic Homo to display modern human development characteristics. Seselj and Konigsberg (2020) reach a different conclusion, arguing that relatively retarded growth rates were also present in early members of the genus Homo in Africa and the Levant.
Access to Xujiayao
The Xujiayao collection is housed in the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China. Research workers interested in access to Xujiayao should write to Professor Wu Xinzhi, Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, PO Box 164, Beijing, Peoples Republic of China.
Ao, H., Liu, C-R., Roberts A.P., Zhang, P., Xu, X. (2017) An updated age for the Xujiayao hominin from the Nihewan Basin, North China: Implications for Middle Pleistocene human evolution in East Asia. Journal of Human Evolution 106: 54-65.
Brown P (1987) Cranial vault thickness in Northern Chinese, European and Australian Aboriginal populations. Acta Anthropologica Sinica 6:10-15.
Chen T, Yuan S, and Gao S (1984) The study of uranium series dating of fossil bones and an absolute age sequence for the main Paleolithic sites of north China. Acta Anthropologica Sinica 6:249-254.
Chen T, Yuan S, Gao S, Wang L, and Zhao G (1982) Uranium series dating of Xujiayao (Hsu-chia-yao) site. Acta Anthropologica Sinica 1:91-95.
Jia L, Wei Q, and Li C (1979) Report on the excavation of the Hsuchiayao Man site in 1976. Vertebrata PalAsiatica 17:277-293.
Li, J.S., Bunn, H.T, Zhang, S.Q., Gao, X. (2017) Equid prey acquisition and Archaic Homo adaptability at the early Late Pleistocene site of Xujiayao, China, International Journal of Osteoarchaeology, 28: 75-82.
Seselj, M., Konigsberg, L.W. (2020) A different interpretation of dental development stages in Xujiayao 1 Middle to Late Pleistocene Homo erg. Journal of Human Evolution 148 (2020) 102745
Trinkaus, E.,Wu, X-J. (2017) External auditory exostoses in the Xuchang and Xujiayao human remains: Patterns and implications among eastern Eurasian Middle and Late Pleistocene crania, PLOS ONE, 10.1371/journal.pone.0189390, 12, 12, (e0189390).
Wu M (1980) Human fossils discovered at Xujiayao site in 1977. Vertebrata PalAsiatica 18:227-238.
Wu R, Wu X, and Zhang S, eds. (1989) Early humankind in China. Beijing: Science Press.
Wu X, and Poirier FE (1995) Human evolution in China. Oxford: Oxford University Press.
Wu X-J, Xing S, Trinkaus E (2013) An Enlarged Parietal Foramen in the Late Archaic Xujiayao 11 Neurocranium from Northern China, and Rare Anomalies among Pleistocene Homo. PLoS ONE 8(3): e59587. doi:10.1371/journal.pone.0059587
Wu X, and Trinkaus E (In Press) Xujiayao 14 mandibular ramus and Pleistocene Homo mandibular variation. Compt. Rend. Palevol.
Xing, S. et al (2020) A broader perspective on estimating dental age for the Xujiayao juvenile, a late Middle Pleistocene archaic hominin from East Asia. JHE 148:
Table 1. Some dimensions of the Xujiayao bones and teeth (mm)
|parietal n.6||parietal n.10|
|Thickness at lambda||7.3||10.2|
|Thickness at tuberosity||5.9||12.8|
|Thickness at vertex||6.8||8.0|
|Thickness at bregma||-||7.7|
|occipital n. 7||occipital n. 15|
|Thickness at lambda||11.0||10.4|
|Thickness at ext. protuberance||18.3||17.8|
|Thickness at int. protuberance||17.4||16.4|
|first molar||isolated m2|