August 12, 2006

Evolutionary distinctiveness of modern humans vs. Neandertals

Erik Trinkaus (see also Early Modern Humans) has an article on the distinctiveness of modern humans vs. Neandertals. By comparing modern humans and Neandertals with early Homo he found out that both Neandertals and modern humans possess several derived (evolved) features: some of them are shared by the two species, but modern humans have more such distinctive features than Neandertals; thus, they are more "different" from early Homo than Neandertals. His conclusion?
When these data on probable trait polarities are combined and one appropriately uses the available data from the entire skeleton and dentition, it is not the Neandertals who appear unusual, special, derived, autapomorphous. It is we.

Perhaps, rather than trying to document the deviant nature of the Neandertals, we should be more focused on understanding the complex evolutionary processes that led from Middle Pleistocene archaic members of the genus Homo to the emergence and eventual dispersal of people anatomically similar to ourselves. Some of this may be explainable in stochastic terms, and the distributions of a variety of the traits considered here should best be seen as influenced primarily by genetic drift and isolation-by-distance in a geographically widespread species. However, other traits may well have selective valences or, more likely, be reflections of selective forces on human biology. But as long as it is regional variants of archaic Homo that are considered in need of explanation and the emergence and subsequent domination of modern humans are taken as given, it is unlikely that the appropriate questions will be framed.

Current Anthropology, volume 47 (2006), pages 597–620

Modern Human versus Neandertal Evolutionary Distinctiveness

Erik Trinkaus

Considerations of morphological variation among later Pleistocene human groups have focused principally on the distinctiveness of the Neandertals of western Eurasia relative to their predecessors and to penecontemporaneous and recent modern humans. In this discussion, there has been a dearth of attention of the degree to which modern humans are derived relative to earlier members of the genus Homo. Of 75 cranial, mandibular, dental, axial, and appendicular traits in which the Neandertals and/or modern humans are derived relative to Early and Middle Pleistocene Homo, approximately one-quarter are shared among Neandertals and modern humans, a similar percentage largely unique to the Neandertals, and about half largely unique to modern humans. The results are similar whether the Neandertals are compared with the earliest modern humans or with their Late Pleistocene and more recent modern human successors. Even though these figures could shift modestly through variation in trait selection and/or as a result of a more complete earlier Pleistocene Homo fossil record, it is apparent that modern humans are morphologically more derived than the Neandertals. Our focus should therefore be at least as much on the evolutionary biology of early and recent modern humans as on that of the Neandertals.


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