Costal process of the first sacral vertebra: Sexual dimorphism and obstetrical adaptation

Tague, Robert G.

doi:10.1002/ajpa.20531

Cited by 35 publications

(57 citation statements)

References 62 publications

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“…The present study followed Erken et al's method (2002) and combined both sexes into a single sample for the analysis in Table 3. This is appropriate because though males are typically larger than females in lengths of the costal and transverse processes (results of this sexual dimorphism from this study are not presented; Tague, 2007), there is no significant difference in the frequencies of females and males in the two samples: with sacralization, 44 females and 56 males (44% and 56%, respectively); without sacralization, 84 females and 100 males (46% and 54%, respectively; chi-square test, v 2 ¼ 0.071, df ¼ 1, P ¼ 0.79). Results of the comparison of costal and transverse process lengths between those with and without sacralization show that the only significant differences are that individuals with sacralization have longer costal processes than those without sacralization for vertebra 24 and the last lumbar vertebra (last lumbar vertebra is vertebra 24 for some individuals and vertebra 25 for others; Table 3).…”

Section: Resultsmentioning

confidence: 94%

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Sacralization is not associated with elongated cervical costal process and cervical rib

Tague

2010

Clinical Anatomy

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Cervical rib/elongated costal process of the seventh cervical vertebra and sacralization of a lumbar vertebra are associated with clinical problems-neurological, vascular, and obstetrical. A previous study reported an association between these morphologies, and suggested that clinicians use presence of one trait to predict presence of the other. This study tested three hypotheses from this association: costal process length among individuals with sacralization differs from that among individuals without sacralization for: (1) only the seventh cervical vertebra, (2) only transitional presacral vertebrae-seventh cervical, twelfth thoracic, and fifth lumbar, and (3) presacral vertebrae in general. Skeletons of 961 individuals between ages 20 and 49 years from the United States were surveyed for sacralization. Costal process length was measured on 100 individuals with sacralization and 184 without sacralization for cervical vertebrae 3 to 7, thoracic vertebrae 11 and 12, and all lumbar vertebrae. Cervical rib was evaluated for 102 individuals with sacralization and 472 without sacralization. Results showed that 11% (105 of 961) of individuals have sacralization. Compared to individuals without sacralization, those with sacralization: (1) have significantly longer costal process for the last lumbar vertebra, but are nonsignificantly different for costal process lengths of other vertebrae, (2) are nonsignificantly different in prevalence of cervical rib-2.9% with sacralization and 0.4% without sacralization, and (3) are significantly more likely to have an extra presacral vertebra. Clinically, results suggest that sacralization is not a predicate for either cervical rib or elongated costal process of the seventh cervical vertebra.

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Section: Resultsmentioning

confidence: 94%

“…ences only for costal process length of vertebra 6 in females (whites larger than blacks) and transverse process lengths of vertebrae 3 in females and 4 in males (whites larger than blacks for both; results not presented; also see Tague, 2007). Therefore, combining blacks and whites into a single sample for analysis in Table 3 was appropriate.…”

Section: Resultsmentioning

confidence: 95%

Sacralization is not associated with elongated cervical costal process and cervical rib

Tague

2010

Clinical Anatomy

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“…Indeed, the present results, where the female os coxae appears consistently smaller than the male one, suggest that differences in the shape of the bones must be responsible for the relatively (and often absolutely) larger female pelvic cavity. Variation in the shape of the sacrum can also contribute to the size of the birth canal, although males have on average larger sacra (Tague, 2007).…”

Section: Discussionmentioning

confidence: 99%

Sexual dimorphism in the size and shape of the os coxae and the effects of microevolutionary processes

Betti

2013

American J Phys Anthropol

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Sexual dimorphism in the human pelvis has been studied widely for forensic purposes, but it is still unclear to what extent it varies among human populations. There is evidence that microevolutionary processes, both neutral (i.e., population history) and selective (e.g., thermoregulatory adaptation and size-related obstetrical constraints) contribute to explain pelvic variation among populations, but the extent to which these factors affect pelvic sexual dimorphism is unknown. In this study, I analyze sexual dimorphism of the os coxae in 20 globally distributed human populations, using 3D morphometric data to separate the size and shape components of sexual differences. After evaluating population differences in the degree and pattern of sexual dimorphism, I test for the effect of population history, climate, and body size in shaping global diversity. The results show that size and shape dimorphism follow different patterns. Coxal size dimorphism is generally quite consistent through populations, with males bigger than females, but it appears to be reduced in small-bodied populations, possibly in relation to obstetrically-related selective pressures for a spacious birth canal. Beyond a general species-wide pattern of shape dimorphism, commonly used for forensic sex determination, other aspects of sexual differences in coxal shape vary among human populations, reflecting the effects of neutral demographic processes and climatic adaptation.

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“…Solid lines are directly measured variables; dashed lines are computed variables. Figure 3A,C-E are reproduced or modified from Tague and Lovejoy (1998); Figure 3B,C are modified from Tague (2007). a Individuals with nonassimilated sacrum had the modal number of precoccygeal vertebrae: 7 cervicals, 12 thoracics, 5 lumbars, and 5 sacral (Standring, 2005).…”

Section: Methodsmentioning

confidence: 99%

High assimilation of the sacrum in a sample of American skeletons: Prevalence, pelvic size, and obstetrical and evolutionary implications

Tague

2008

American J Phys Anthropol

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High assimilation sacrum is fusion of the caudal-most lumbar vertebra to the first sacral vertebra. Previous studies have shown that high assimilation is associated with clinical problems, including obstetrical difficulty. This study used adult American males (n = 1,048) and females (n = 1,038) of the Hamann-Todd and Terry skeletal collections to determine the prevalence of high assimilation and its effect on pelvic size, and to consider the obstetrical and evolutionary implications of high assimilation. The prevalence of high assimilation in this sample is 6.3%, with males and females not differing significantly from one another in their prevalence. This prevalence is near the median for that reported in 41 other samples. In both males and females, individuals with high assimilation have significantly longer anteroposterior and posterior sagittal diameters of the inlet, and shorter sacrum compared to those with a nonassimilated sacrum. Females with high assimilation have a significantly narrower sacral angulation (i.e., reduced inclination of ventral axis of sacrum), and shorter posterior sagittal diameter of the outlet compared to those with a nonassimilated sacrum. A short posterior sagittal diameter of the outlet is associated with childbirth difficulty. As high assimilation is partial homeotic transformation of a lumbar vertebra, this study supports previous research that homeotic transformation of vertebrae is selectively disadvantageous.

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Costal process of the first sacral vertebra: Sexual dimorphism and obstetrical adaptation

Cited by 35 publications

References 62 publications

Sacralization is not associated with elongated cervical costal process and cervical rib

Sacralization is not associated with elongated cervical costal process and cervical rib

Sexual dimorphism in the size and shape of the os coxae and the effects of microevolutionary processes

High assimilation of the sacrum in a sample of American skeletons: Prevalence, pelvic size, and obstetrical and evolutionary implications

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