The late quaternary Hominins of Africa: The Skeletal evidence from MIS 6-2

Abstract

The late Quaternary African hominin fossil record provides a tantalizing glimpse into considerable temporal and geographic morphological diversity within the genus Homo. A total of 50 sites that can be constrained from MIS 6-2 have yielded specimens ranging from isolated teeth to nearly complete skeletons. However, only a dozen or so provide particularly informative or interesting evidence spanning this period of nearly 200 kyr. In addition to the rather paltry nature of the record, one of the seemingly more intractable problems that bedevil its interpretation is the nature of the chronometric record for many of the sites. The Late Pleistocene terrestrial climatic record for Africa is also rather patchy, making continent-wide generalizations difficult. Attempts to link large-scale environmental perturbations in Africa to patterns of human evolution and behavior are even more problematic. Although the African fossil (and archaeological) record is most often viewed from the perspective of a single lineage culminating in the appearance of Homo sapiens and thence modern humans, the degree of morphological diversity evident even in this meager assemblage can be rather striking. Some of this diversity may be related to geographic and/or temporal differences, but in other instances, there are noticeable differences among remains that are contemporaneous, or at least penecontemporaneous. The Late Pleistocene African hominin fossil record, despite its manifestly incomplete nature, finds consistency with an impressive array of genetic evidence that points to an African origin for our species, and it also has consilience with genetic data that indicate a coalescence of lineages to the common ancestor of Homo sapiens at around the beginning of MIS 6. Although multiple lines of genetic evidence indicate a deep separation of lineages, with the ancestors of the southern African Khoesan diverging early on from that which gave rise to all other groups, there is a notable paucity of human remains that predate MIS 2 that exhibit strong phenetic resemblance to recent African populations. A number of the human dental samples from Late Pleistocene South African sites possess morphological variants that characterize the teeth of the recent inhabitants of sub-Saharan Africa, but these similarities do not necessarily signify a close evolutionary relationship with any of these populations because they appear to be plesiomorphic.