The Neanderthal skull offers a unique window into the divergent evolutionary paths of the Homo genus. Neanderthals, an extinct group of archaic humans, possessed a cranial architecture notably distinct from modern Homo sapiens. Their head shape, characterized by a long, low braincase, reflects a different pattern of brain growth and organization. Analyzing these morphological differences helps paleoanthropologists understand the biology and potential cognition of our closest extinct relatives.
Defining the Distinctive Features
The Neanderthal skull is immediately recognizable by its elongated, football-like shape, contrasting sharply with the rounded form seen in modern humans. This long, flat cranial vault gives the head a low profile when viewed from the side. The most prominent feature above the face is the supraorbital torus, a heavy, rounded brow ridge that forms a pronounced shelf of bone over the eye sockets.
At the rear of the skull, Neanderthals exhibit a distinct bony projection known as the occipital bun, or chignon. This bulge contributes significantly to the elongated appearance of the cranium and is correlated with a flatter parietal profile. The Neanderthal face projects forward in the midline, a feature called mid-facial prognathism, particularly noticeable in the large, wide nasal opening and high, rounded eye orbits.
The overall structure results in what is sometimes described as an “en bombe” or bomb-like shape when viewed from the back. This combination of a projecting face, a low forehead, and a prominent occipital bun constitutes a specific anatomical adaptation that developed gradually in European populations during the Middle Pleistocene.
Developmental Basis of the Shape
The elongated Neanderthal cranium results from a fundamentally different process of postnatal development than that of modern humans. Both Neanderthal and modern human newborns initially possess elongated braincases at birth. The divergence in shape occurs significantly during the first year of life.
Modern humans undergo a distinct phase of development called “globularization,” where the braincase rounds out and becomes higher, a process absent in Neanderthals. The Neanderthal skull, conversely, continues to grow in a more elongated fashion, maintaining its long and low shape throughout development. This difference in early growth trajectories suggests that the final adult brain shape is rooted in distinct genetic and developmental mechanisms.
Neanderthal genetic variants found in present-day humans are associated with slightly less globular heads, revealing a genetic underpinning for this morphological difference. The specific genes involved are linked to neurogenesis and myelination, suggesting that subtle differences in the timing and pattern of brain development contributed to the adult cranial divergence.
Implications for Brain Organization
While Neanderthal brains were similar in size or even slightly larger than those of modern humans, their distinctive shape suggests differences in how the brain matter was organized. The elongated cranium resulted in flatter parietal lobes, a region associated with higher-order functions like spatial reasoning and visuospatial integration. Modern humans, with their globular skulls, show a vertical and anteroposterior expansion of the parietal lobes.
Neanderthals appear to have allocated proportionally more tissue to other areas. For example, they had significantly larger eye sockets, suggesting they possessed larger visual cortices in the back of the brain. This larger visual system may have been an adaptation to the lower light conditions found at the high latitudes of Ice Age Europe.
The increased neural investment in vision and the larger body size of Neanderthals meant that a greater proportion of their brain volume was dedicated to basic somatic and visual processing. This potentially left a smaller amount of neural tissue available for functions related to social cognition and complex social networking, which are often linked to the parietal and frontal lobes. Differences in the connectivity of specific brain regions have also been suggested based on the analysis of Neanderthal-derived DNA fragments in modern humans.
Contrasting with Modern Human Crania
The modern human skull is characterized by its high, vertical forehead, which rises sharply above the orbits. This contrasts with the low, sloping forehead seen in Neanderthals, which is overshadowed by the heavy supraorbital torus. Globularization in modern humans is accompanied by the near-total reduction or absence of the massive brow ridge.
The face of Homo sapiens is retracted beneath the forehead, meaning the face is tucked under the front of the cranium rather than projecting forward. Furthermore, the back of the modern human skull lacks the prominent occipital bun seen in Neanderthals.