Geographic variation in human tooth enamel thickness does not support Neandertal involvement in the ancestry of modern Europeans

Neandertals are reportedly characterized by unusually thin molar enamel in comparison to other fossil and recent humans. This, together with other evidence for an accelerated rate of tooth crown formation and a concomitantly shorter period of somatic maturation, has been used to argue that the Neandertals represent a collateral branch of our evolutionary lineage that went extinct without Issue (the 'African Replacement' model of modern human origins). By contrast, it has also been claimed that Neandertals are encompassed by the modern human range of variation in enamel structure and thickness, and that their closest affinities in this regard are with modern Europeans among geographically diverse populations. The sharing of thin enamel by Neandertals and subsequent Europeans would be consistent with arguments to the effect that the former contributed to the ancestry of the latter (the 'Multiregional' model of modern human origins). Evaluation of this purported synapomorphy through an examination of the permanent molars of recent Europeans and Africans reveals that they are indistinguishable from one another in enamel thickness. Thus, modern Europeans do not share relatively thin molar enamel with Neandertals. Rather, thin tooth enamel would appear to represent an ostensibly autapomorphic feature by which they differ from modern as well as other fossil humans.