A re-evaluation of the metric diversity within Homo erectus.

Previous work by several researchers has suggested that the cranial sample from Zhoukoudian possesses a unique metric pattern relative to the African and Asian specimens assigned to Homo erectus. The current study readdresses this issue with an expanded fossil sample and a larger and more comprehensive set of cranial measurements. To test the patterns present in the assemblage, canonical variates analysis was performed using a covariance matrix generated from the Howells data set. From this, interindividual Mahalanobis distances were computed for the fossils. Random expectation statistics were then used to measure statistical significance of the Mahalanobis distances. The results show that the Zhoukoudian hominids exhibit a unique metric pattern not shared by the African and Indonesian crania sampled. In these tests the Hexian calvaria resembled the African and Indonesian specimens and differed significantly from the craniometric pattern seen in the Zhoukoudian fossils. The Zhoukoudian specimens are characterized by a wide midvault and relatively narrow occipital and frontal bones, while the African and Indonesian crania (including Hexian) have relatively broad frontal and occipital dimensions compared to their midvaults. These results do not suggest that a multiple-species scenario is necessary to encompass the variation present in the sample. Based on the current evidence it is more probable that this variation reflects polytypism influenced by environmental adaptation and/or genetic drift.