The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


The developmental and evolutionary significance of occipital bunning: A comparative morphometric study

MIRANDA E. UTZINGER1, ROBERT G. FRANCISCUS1 and THOMAS E. SOUTHARD2.

1Anthropology, University of Iowa, Iowa City, IA, 2Orthodontics, University of Iowa, Iowa City, IA

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The occipital bun has long been cited as a diagnostic Neandertal trait, but a degree of bunning can also be found on some anatomically modern human crania. Scholars have proposed many explanations for the development and significance of occipital bunning, including hypotheses about variation in nuchal musculature attachment, posterior brain growth mode and tempo, and aspects of craniofacial integration. Because occipital bunning corresponds, at least in part, to underlying growth in the occipital lobe of the brain, this feature may provide insight into brain growth and development in past populations.

This study incorporates both fossil and extant human comparisons in order to better understand the timing and significance of occipital bun development. Morphometric data were obtained from Neandertal, early modern human, and recent modern human crania. Major landmark points and data streaming measurements of the occipital region were taken to capture surface curve data. Cranial capacity and cranial base measurements were also taken to assess cranial integration hypotheses. These morphometric data show a clear differentiation between Neandertal and modern human bun morphology.

Posterior cranial shape in extant modern humans was also assessed using cranial radiographs from the Iowa Growth Study, allowing a true longitudinal study of occipital bone growth. Preliminary analysis of these radiographs shows that bun morphology, when present, appears early in childhood, becoming more defined with age. Evidence of a posterior cerebral growth spurt is not supported by these data. Instead, bun development in extant humans appears to be a slow, uniform process occurring into late adolescence.

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