Within-group human variation in the Asian Pleistocene: the three Upper Cave crania

Numerous studies on Pleistocene samples have shown that within-group cranial variation was greater than that seen today. The three anatomically modern Upper Cave crania (UC 101, UC 102, and UC 103) from Zhoukoudian, China provide one of the best samples available for addressing the issue of the antiquity of the modern pattern of within-group cranial variability because archaeological evidence indicates that they are spatially and temporally restricted. Research on the Upper Cave fossils usually only includes UC 101 and UC 103 because of postmortem damage to UC 102's cranial vault. However, the face of UC 102 is undamaged, allowing for most facial measurements to be performed accurately. In this study we use facial dimensions to compare all three Upper Cave specimens, and we evaluate whether the variation seen among them is larger than that observed in extant populations. Using a worldwide sample of modern populations to establish a baseline, the three Upper Cave crania were compared to each other. Since there is disagreement over the sex of UC 102, this specimen is treated alternately as a female and as a male. Results show that the Upper Cave specimens exhibit significantly more variation than do individuals within more recent human populations, especially if UC 102 is considered male. Furthermore, results indicate that the fossils never fall into the same modern human group, and that each specimen is significantly atypical of its nearest modern neighbor in multivariate space. We conclude that the three Upper Cave crania do not represent a family group but are representative of the larger contemporaneous heterogeneous Asian Pleistocene population. Our results support the contention that today's within-group homogeneity is a relatively recent phenomenon, and is likely the result of a Neolithic population expansion and its many effects.