The morphological distinctiveness of Homo sapiens and its recognition in the fossil record: Clarifying the problem

Abstract

AbstractSpecies are historically differentiated entities that, osteologically, may be differentiated to inconveniently varying extents. Living Homo sapiens is a distinctive morphological entity that is easily distinguished in both cranial and postcranial morphology from all other living hominoids and from the vast majority of its fossil relatives. In this contribution, we offer several apparent cranial apomorphies of the living species, while recognizing that it is reasonable to expect some degree of overlap in the ranges of variation of individual characters among closely related species such as those within the genus Homo. No one aspect of morphological detail may be considered totally diagnostic within very close‐knit groups of this sort or, conversely, be regarded as blurring the identities of their components. Overlap in morphological detail may even be expected in cases where striking Gestalt differences exist between closely related species due to major developmental reorganization. As a result, while the morphological and, by extension, historical distinction between such highly differentiated species pairs as Homo neanderthalensis and Homo sapiens is effectively unequivocal, in a nod to the intrinsic untidiness of biology the hominid fossil record does offer some instances that are much more difficult to interpret. In such cases, most, but not all, of the cranial apomorphies of living Homo sapiens, are present in individual fossil specimens or apparent populations. This is true, for example, of a set of variably dated and archeologically associated, as well as mostly incomplete, South African fossils (for example, Border Cave, Boskop, Fish Hoek, and most Klasies River Mouth specimens). These specimens very closely resemble living Homo sapiens in preserved overall cranial structure, but most conspicuously lack bipartite brows and fully developed human chin configurations. Whatever resolutions hominid systematists may reach in such cases, it is clear that to resort reflexively to such pernicious if convenient devices as “archaic Homo sapiens” only obscures any potential signals of systematic diversity in what is increasingly evidently a highly complex late Pleistocene hominid record.