The two Yuanmou maxillary central incisor teeth were found by the geologist Fang Qian in 1965 on a small hill near Yuanmou city, Yunan Province. Excavations of the area by the Institute of Vertebrate Paleontology and Paleoanthropology in 1973 recovered faunal material. The teeth were described by Hu (1973) and Zhou and Hu (1979). On the basis of their size, morphology and presumed age the teeth have been assigned to Homo erectus.

A complicated site stratigraphy has contributed to the debate over the age of the hominid remains at Yuanmou (Cheng et al., 1977; Han and Xu, 1989; Li et al., 1979; Liu and Ding, 1983; Liu and Ding, 1984; Pan et al., 1991; Qian et al., 1991; Qing, 1985). The precise location of the teeth in the deposit and their relationship to the dated horizons and faunal remains is also unclear. Reworking of the deposit may be an issue as they are of fluvial and deluvial origin. According to Qian et al. (1991) palaeomagnetic dates from near where the teeth were recovered average 1.7 myr. However, Liu and Ding (1984) noted that the faunal sequence at the site was inverted, with more extinct species in the upper levels than deeper in the deposit. They suggest that a date of 600,000 to 500,000, Bruhnes rather than Matuyama Epoch, was most appropriate. The younger date is more consistent with the current state of knowledge on the dispersion and evolution of hominids in Asia.

The incisor teeth are large and robust in comparison with those in modern Homo sapiens. Tooth morphology and wear patterns indicate that they are from the same individual which is an unusual circumstance given the nature of the deposit. The incisors have a prominent basal tubercle on the lingual surface of the crown, with ridges extending from the tubercle to the incisive edge on the mesial and lateral sides. Between these ridges the surface appears scooped out, with fine projections extending from the tubercle into the scooped out surface. The overall effect is of a classic "shovel shaped" incisor tooth. The labial surface of the tooth is relatively flat, apart from some fine grooves. The tooth roots are robust and somewhat flattened antero-posteriorly. Part of the root for the right incisor is not preserved. While these teeth are similar to those described for Zhoukoudian Homo erectus this is not enough to indicate that they must be H. erectus teeth. For instance, an incisor tooth of similar size and morphology is present in the Xujiayo archaic H. sapiens maxilla, as well as Krapina Neandertals (see photograph below).

 Krapina Neandertal maxilla K, photograph © Milford Wolpoff

Recent research

In 2008 Zhu and colleagues reported paleomagnetic dates for the layer in which the Yuamou incisor teeth were found. They concluded, that the hominin-bearing layer resides in a reverse polarity magnetozone just above the upper boundary of the Olduvai subchron, yielding an estimated age of 1.7 Ma. The finding represents the age of the earliest documented presence of Homo, with affinities to Homo erectus, in mainland East Asia.

R.X. Zhu, R. Potts, Y.X. Pan, H.T. Yao, L.Q. Lü, X. Zhao, X. Gao, L.W. Chen, F. Gao, C.L. Deng. 2008. Early evidence of the genus Homo in East Asia. Journal of Human Evolution, 55: 1075-1085

http://humanorigins.si.edu/research/asian-research/earliest-humans-china

References

Cheng G, Li S, and Lin J (1977) Discussion of the age of Homo erectus yuanmouensis and the event of early Matuyama. Scientia Geologica Sinica 1:34-43.

Han D, and Xu C (1989) Quaternary mammalian faunas in south China. In R Wu, X Wu and S Zhang (eds.): Early humankind in China. Beijing: Science Press, pp. 338-391.

Hu C (1973) Ape-man teeth from Yuanmou, Yunnan. Acta Geologica Sinica 1:65-71.

Li P, Qian F, Ma X, Pu Q, Xing L, and Ju S (1979) A preliminary study of the age of Yuanmou Man by palaeomagnetic techniques. Scientia Sinica 6:579-591.

Liu T, and Ding M (1983) Discussion on the age of 'Yuanmou Man'. Acta Anthropologica Sinica 2:40-48.

Liu T, and Ding M (1984) A tentative chronological correlation of early fossil horizons in China with loess-deep sea records. Acta Anthropologica Sinica 3:93-101.

Pan Y, Li Q, Lin Y, and Jiang C (1991) Late Pleistocene fauna discovered in Yuanmou basin, Yunnan. Acta Anthropologica Sinica 10:167-175.

Qian F, Li Q, Wu P, Yuan S, Xing R, Chen H, and Zhang H (1991) Lower Pleistocene, Yuanmou Formation: Quarternary Geology and Paleoanthropology of Yuanmou, Yunnan, China. Beijing: Science Press, pp. 17-50.

Qing F (1985) On the age of "Yuanmou Man"-a discussion with Liu Tungsheng et al. Acta Anthropologica Sinica 4:324-332.

Zhou G, and Hu C (1979) Supplementary notes on the teeth of Yuanmou man with a discussion on morphological evolution of the mesial incisors in hominoids. Vertebrata PalAsiatica 17:149-162.