Evolution of the zygomaticomaxillary region in the genus Homo and its relevance to the origin of modern humans

Abstract

Metrical and non-metrical analyses of the midfacial region of the genus Homo as viewed in norma frontalis reveal distinct geographical differences in cheek morphology which do not support a replacement model for the origin of modern humans. With the recovery of new Asian fossil hominids it is now clear that fossil Asian faces contrast markedly with many European and African contemporaries. Fossil Asians exhibit much smaller upper and lower midfaces with more horizontally oriented zygomatic bones, pronounced and more medially situated malar tubercles, a distinct incisura malaris, a more acute and inferiorly situated zygomaticomaxillary angle and a vertically shorter maxilla. In comparison with African and Eurasian populations, all these features are also found in higher frequencies in extant Mongoloid populations. European fossil hominids exhibit larger upper and lower facial areas, obliquely oriented zygomatic bones, vertically taller maxillae and zygomatic bones which lack a malar tubercle and incisura malaris. Both Europeans and Mongoloids diverge from the conditions seen in specimens of early Homo in Africa. Morphological traits previously restricted only to fossil Asians now occur in all populations of modern humans. However, their frequency remains higher in populations deriving from or occupying the Far East. The world-wide dissemination of morphological traits which first appeared in the Asian fossil record, suggest that at least some of the facial traits associated with the emergence of modern humans, resulted not from a single African origin, but from admixture and gene flow between different regions of the Old World.