Cranial Shape in Asian Homo erectus: Geographic, Anagenetic, and Size-Related Variation

Abstract

A strong focus on the morphological ­differences between African and Asian H. erectus has generally overshadowed variation among populations of Asian H. erectus. This study explored variation in Asian H. erectus using 3D geometric morphometric methods, examining the shape of the neurocranium, frontal bone, occipital bone and temporal base. Analyses focused on the elucidation of geographic, temporal and size-related patterns of cranial shape variation in a representative sample from Zhoukoudian, Sangiran, Ngandong, Sambungmacan and Ngawi. In regards to the neurocranium, geographic differences explained the greatest proportion of variation, followed by geochronological age (these two factors explained similar shape differences within the neurocranium) and size. The temporal base, frontal and occipital bones were strongly influenced by geography and size. Although the later Javanese and Zhoukoudian specimens were generally distinct, there was some overlap between Sangiran 2 and the northern Chinese specimens. This may suggest that isolation between the two regions did not occur until the Middle or Late Pleistocene or that the Sangiran hominins are morphologically close to the common ancestor of the Zhoukoudian and later Javanese H. erectus. The late Indonesian fossils did group together in the principal components analyses. Yet there were subtle shape differences between the Sambungmacan/Ngawi fossils and those from Ngandong, indicating the presence of two similar but slightly different potentially contemporaneous morphs. The Sambungmacan specimens do not appear to be morphological intermediaries between the Sangiran and Ngandong fossils in regards to overall cranial shape.