1. Anthropologisches Institut and Institut für Informatik/MultiMedia Laboratorium Universität Zürich-Irchel, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
2. The authors contributed equally to this work

Correspondence to: Correspondence and requests for materials should be addressed to C.Z. (e-mail: Email: zolli@ifi.unizh.ch).

Abstract

Homo neanderthalensis has a unique combination of craniofacial features that are distinct from fossil and extant 'anatomically modern' Homo sapiens (modern humans). Morphological evidence, direct isotopic dates¹ and fossil mitochondrial DNA from three Neanderthals^{2, 3} indicate that the Neanderthals were a separate evolutionary lineage for at least 500,000 yr. However, it is unknown when and how Neanderthal craniofacial autapomorphies (unique, derived characters) emerged during ontogeny. Here we use computerized fossil reconstruction⁴ and geometric morphometrics^{5, 6} to show that characteristic differences in cranial and mandibular shape between Neanderthals and modern humans arose very early during development, possibly prenatally, and were maintained throughout postnatal ontogeny. Postnatal differences in cranial ontogeny between the two taxa are characterized primarily by heterochronic modifications of a common spatial pattern of development. Evidence for early ontogenetic divergence together with evolutionary stasis of taxon-specific patterns of ontogeny is consistent with separation of Neanderthals and modern humans at the species level.