Developmental age and taxonomic affinity of the Mojokerto child, Java, Indonesia

Abstract

An increasing number of claims place hominids outside Africa and deep in Southeast Asia at about the same time that Homo erectus first appears in Africa. The most complete of the early specimens is the partial child's calvaria from Mojokerto (Perning I), Java, Indonesia. Discovered in 1936, the child has been assigned to Australopithecus and multiple species of Homo, including H. modjokertensis, and given developmental ages ranging from 1-8 years. This study systematically assesses Mojokerto relative to modern human and fossil hominid growth series and relative to adult fossil hominids. Cranial base and vault comparisons between Mojokerto and H. sapiens sapiens (Hss) (n = 56), Neandertal (n = 4), and H. erectus (n = 4) juveniles suggest a developmental age range between 4 and 6 years. This range is based in part on new standards for assessing the relative development of the glenoid fossa. Regression analyses of vault arcs and chords indicate that H. erectus juveniles have more rounded frontals and less angulated occipitals than their adult counterparts, whereas Hss juveniles do not show these differences relative to adults. The growth of the cranial superstructures and face appear critical to creating differences in vault contours between H. erectus and Hss. In comparison with adult H. erectus and early Homo (n = 27) and adult Hss (n = 179), the Mojokerto child is best considered a juvenile H. erectus on the basis of synapomorphies of the cranial vault, particularly a metopic eminence and occipital torus, as well as a suite of characters that describe but do not define H. erectus, including obelion depression, supratoral gutter, postorbital constriction, mastoid fissure, lack of sphenoid contribution to glenoid fossa, and length and breadth ratios of the temporomandibular joint. Mojokerto is similar to other juvenile H. erectus in the degree of development of its cranial superstructures and its vault contours relative to adult Indonesian specimens. The synapomorphies which Mojokerto shares with H. erectus are often considered autapomorphies of Asian H. erectus and confirm the early establishment and long-term continuity of the Asian H. erectus bauplan. This continuity does not, however, necessarily reflect on the pattern of origin of modern humans in the region.

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