A study of the sacrum and some aspects of presacral vertebrae in San (Bushmen) and Southern African and American Negroes
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Date
2015-02-20
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Abstract
The sacrum of the South African Negro and the San was investigated to
determine, firstly, whether the tribal sub-groups which comprise the
S.A. Negro sample (Natal Nguni, Cape Nguni and Sotho) could be
distinguished from one another on the basis of sacral metrical
characters; and secondly, the relationships between the S.A.
Negro and the San. In addition, the numbers of precoccygeal vertebrae
in the S.A. Negro (including the tribal sub-groups) and in the San are
analysed. The groups were further compared with the American Negro
vertebral columns.
The number of sacral vertebrae and transitional features at the
lumbo-sacral and sacrococcygeal junctions are correlated with
numerical spinal formulae and total precoccygeal vertebral number.
A developmental explanation is sought to explain the findings.
The S.A. Negro and San vertebral columns are drawn from the
R.A. Dart Collection of African Skeletons. The San sample is augmented
from other Collections in South africa. The American Negro vertebral
columns are derived from the R.J. Terry and Hamann-Todd Collections in
the United States of America.
The sacral metrical analysis reveals no major differences among the
S.A.'Negro tribal sub-groups which are pooled to provide a sample
representative of the S.A. Negro. Comparison of S.A. Negro and San
sacra reveals significant differences mainly of size between the two
groups. The sacral metrical analysis is based on comparisons of
individual mean metrical sacral characters and on the results of an
analysis of morphological divergence, Mahalanobis's Generalised
Distance Statistic, D2 .
There is an exceptionally high frequency of an increase in the
number of precoccygeal vertebrae (PCV) in San males, S.A. Negro males
and to a lesser extent, in American Negro males as compared with other
populations This trend is present, too, in females though female
spines are more likely to have a decreased number of PCV and males an
increased number of PCV. The tendency towards an increased number of
PCV seems to be a population or racial trend in these groups though
with sex-dependent variations in the penetrance of the trait.