Recent studies have shown that the Neandertals had far more sophisticated behavioral practices than we once gave them credit for. But were these beetle-browed hominids actually members of our own species? To date, this long-standing debate has focused on morphological data from fossils belonging to adult Neandertals (more recently, data from fossilized DNA has entered the picture as well). But a study published today in the journal Nature takes a different tack, using sophisticated computer imaging techniques to assess early Neandertal development, or ontogeny. According to this new analysis, the Neandertals' distinctive cranial features appeared early on, offering support to the idea that these archaic Europeans belonged to a species separate from Homo sapiens.

Starting with CT scans of crania belonging to immature and adult Neandertals, early modern humans, and living modern humans, Swiss researchers Marcia S. Ponce de Len and Christoph P. E. Zollikofer of the University of Zurich generated three-dimensional representations of the specimens. Subsequent analyses conducted using the so-called geometric morphometrics method revealed that the features distinguishing Neandertals and moderns were already present in toddlers. This find, the authors assert, indicates that the characteristic features emerged during early postnatal or prenatal development, instead of taking shape gradually through to adulthood. The team further notes that the Neandertal ontogenetic process occurred at a fast pace relative to that of modern humans.

The early appearance of diagnostic features, the maintenance of these distinctive traits throughout postnatal development, and the evolutionary stability of this pattern, Ponce de Len and Zollikofer conclude, support the theory that Neandertals and anatomically modern humans represent separate species. But whether a similar pattern of developmental diversification characterizes the other hominids, they add, remains to be seen.