Brain development after birth differs between Neanderthals and modern humans

Neanderthals had brain sizes comparable to modern humans, but their brain cases were elongated and not globular as in Homo sapiens [1,2]. It has, therefore, been suggested that modern humans and Neanderthals reached large brain sizes along different evolutionary pathways [2]. Here, we assess when during development these adult differences emerge. This is critical for understanding whether differences in the pattern of brain development might underlie potential cognitive differences between these two closely related groups. Previous comparisons of Neanderthal and modern human cranial development have shown that many morphological characteristics separating these two groups are already established at the time of birth [3-5], and that the subsequent developmental patterns of the face are similar, though not identical [6]. Here, we show that a globularization phase seen in the neurocranial development of modern humans after birth is absent from Neanderthals.