Introduction

There is a great deal of interest in the phylogenetic relationship between Neandertals and anatomically modern humans, and the taxonomic classification of Neandertals is of central importance in the discussion of the origins of anatomically modern humans. There are two prominent hypotheses about modern human origins that offer contrasting views of Neandertal taxonomic status: the recent African origin model posits that Neandertals (Homo neanderthalensis) and modern humans (Homo sapiens) were separate species (e.g., Stringer, 1989, 1992; Stringer & Andrews, 1988; Stringer et al., 1984); while the multiregional model proposes genetic continuity between Neandertals (Homo sapiens neanderthalensis) and early modern humans (Homo sapiens sapiens) in Eurasia (e.g., Wolpoff, 1989; Wolpoff et al., 1984); although less extreme models have also been presented (e.g., Bräuer, 1984; Relethford & Harpending, 1994; Smith, 1992; Smith et al., 1989). Historically, morphological comparisons of Neandertals and modern humans (such as those cited above) have focused almost entirely on adult morphology. However, the study of adult remains alone has failed to answer the question of whether or not Neandertals are a subspecies of Homo sapiens, or a separate species, Homo neanderthalensis.

There is growing awareness that developmental shifts are an important component of evolutionary change (for recent examples, see papers in Minugh-Purvis & McNamara, 2002; O'Higgins & Cohn, 2000). Therefore, the identification of growth processes that differentiate Neandertal and modern human craniofacial morphology is potentially informative about whether or not Neandertals and modern humans belong to the same or to different species, and several recent studies have investigated this idea.