Frontal sinus size in South African Later Stone Age Holocene Khoe-San.

Frontal size variation is comparatively poorly sampled among sub-Saharan African populations. This study assessed frontal sinus size in a sample of Khoe-San skeletal remains from South African Later Stone Age contexts. Volumes were determined from CT scans of 102 adult crania; individual sex could be estimated in 82 cases. Sinus volume is not sexually dimorphic in this sample. The lack of frontal sinus aplasia is concordant with the low incidences recorded for other sub-Saharan African and most other global populations save those that inhabit high latitudes. There is considerable variation in frontal sinus size among global populations, and the Khoe-San possess among the smallest. The Khoe-San have rather diminutive sinuses compared to sub-Saharan Bantu-speaking populations but resemble a northern African (Sudanese) population. Genetic studies indicate the earliest population divergence within Homo sapiens to have been between the Khoe-San and all other living groups, and that this likely occurred in Africa during the span of Marine Isotope Stages 8-6. There is scant information on frontal sinus development among Late Quaternary African fossils that are likely either closely related or attributable to Homo sapiens. Among these, the MIS 3 cranium from Hofmeyr, South Africa, exhibits distinct Khoe-San cranial affinities and despite its large size has a very small frontal sinus. This raises the possibility that the small frontal sinuses of the Holocene South African Khoe-San might be a feature retained from an earlier MIS 3 population.

Variation, sexual dimorphism, and enlargement of the frontal sinus with age in adult South Africans.

OBJECTIVES: To document frontal sinus volume (FSV) in a sample of sub-Saharan Africans with a view to evaluating claims that such populations exhibit comparatively small sinuses. This study also addresses questions related to sexual dimorphism, incidence of sinus aplasia, and the possibility that FSV continues to increase through adulthood. MATERIALS AND METHODS: FSV was measured from CT scans of adult crania from the Dart Collection. Sex and age were known for each individual. Linear cranial dimensions were used to compute a geometric mean from which a scaled FSV was computed for each cranium. RESULTS: FSV does not differ significantly between sexes, but females exhibit a higher incidence of aplasia. There is considerable variation in FSV in this sample, with the average ranking among the higher means reported for other population samples. The incidence of FS aplasia falls within the range of values recorded for other population samples. Although our study is cross-sectional rather than longitudinal, there is strong evidence that FSV continues to increase with age throughout adulthood. DISCUSSION: The FSV mean of our sample contradicts the notion that sub-Saharan Africans possess small sinuses. In a global context, geography (climate and altitude) does not appear to be related to FSV. The absence of sexual dimorphism in our sample is unexpected, as significant dimorphism has been reported for most other population samples. Our results support other indications that the frontal sinus continues to expand throughout adulthood, especially in females, and that it is likely due to bone resorption.

Metopism in adult South Africans and its relationship to frontal sinus size.

This study documents the incidences of complete and partial metopism and their possible relationship to frontal sinus volume (FSV) in a sample of modern adult black South Africans with a view to evaluating the hypothesis that metopism affects frontal sinus hypoplasia. FSV was measured from CT scans and the incidence of metopism was recorded from direct observations of dried cadaveric crania. The sex of each individual was known. Four linear cranial dimensions were used to compute a geometric mean by which to scale FSV. The incidence of partial metopism (38%) is comparable to that reported for other population samples, although there is considerable variation among these global sample frequencies. It is significantly more common in male than female South Africans. FSV in individuals with complete metopism is smaller than average but not inordinately so. On the other hand, FSV is significantly larger in individuals with partial metopism than in those that do not present with this sutural remnant. The data on FSV in individuals with and without partial metopism contradict the hypothesis that there is a relationship between partial metopism and frontal sinus hypoplasia. As such, the metopic remnant evinced by the Late Pleistocene cranium from Hofmeyr, South Africa is unlikely to be related to its very small FSV.