Sacral Variability in Tailless Species: Homo sapiens and Ochotona princeps

Lumbarization and sacralization: Domains of their co-occurrence with other costal-vertebral transformations are not identical

OBJECTIVES

This study evaluates whether sacralization of a lumbar vertebra and lumbarization of a sacral vertebra are a paired duality but with opposite expressions; the former is associated with 23 presacral vertebrae (PSV) and the latter with 25 PSV. Are sacralization and lumbarization local phenomena, involving only vertebra (V) 24 and V25, or are they associated with other costal-vertebral transformations?

MATERIALS AND METHODS

Study sample is of skeletonized humans, 431 females and 1405 males, who were 20-49 years of age-at-death and who died in the United States in the 20th and 21st centuries. Data collected are numbers of PSV and sacral vertebrae, presence of rib of V7, position of diaphragmatic vertebra, and transverse process and rib lengths of V5-V9, V18-V19, and V21-V22.

RESULTS

Females and males differ significantly in numbers of PSV. Both sexes show significant differences among individuals with 23 PSV, 24 PSV, and 25 PSV: (1) individuals with 23 PSV have the shortest ribs, whereas those with 25 PSV have the longest ribs, of V18 and V19; and (2) individuals with 23 PSV have the highest frequency of 6 sacral vertebrae, whereas those with 25 PSV have the highest frequency of 5 sacral vertebrae.

DISCUSSION

Individuals with 23 PSV and 25 PSV show posterior and anterior homeotic transformation, respectively, of the thoracic-lumbar and lumbar-sacral boundaries, but only individuals with 25 PSV show transformation of the sacral-coccygeal boundary. As co-occurring costal-vertebral transformations differ between sacralization and lumbarization, inferentially the set of genes that influences these vertebrae also differs.

Active pelvic movements on a Swiss ball reduced labour duration, pain, fatigue and anxiety in parturient women: a randomised trial

QUESTION

How much do active pelvic movements on a Swiss ball during labour affect maternal and neonatal outcomes?

METHOD

A randomised trial with concealed allocation, blinded assessors and intention-to-treat analysis.

PARTICIPANTS

Two-hundred parturient women.

INTERVENTION

The experimental group performed pelvic anteversion and retroversion, lateral pelvic tilts and circular hip movements according to individual obstetric evaluation (foetal station and position, cervical dilatation and the presence of early pushing urge) on a Swiss ball. The control group received usual care. Both groups were permitted to walk and shower.

OUTCOME MEASURES

The primary outcome was the duration of the first stage of labour. The secondary outcomes were the duration of the second stage of labour, pain intensity, delivery mode, medication use, local swelling, fatigue, anxiety, satisfaction and neonatal outcomes.

RESULTS

The experimental intervention reduced the duration of labour by 179 minutes (95% CI 146 to 213) in stage one and 19 minutes (95% CI 13 to 25) in stage two. It decreased pain by approximately 2 points (95% CI 2 to 2) on a 0-to-10 scale at 30, 60 and 90 minutes. It reduced the risk of a caesarean section (ARR 0.14, 95% CI 0.03 to 0.25; NNT 7, 95% CI 4 to 32) and vulvar swelling (ARR 0.11, 95% CI 0.03 to 0.19; NNT 9, 95% CI 5 to 31). It reduced fatigue by 18 points (95% CI 16 to 21) on a 15-to-75-point scale and anxiety by 9 points (95% CI 8 to 11) on an 18-to-72-point scale. Other effects were negligible or unclear.

CONCLUSION

Active pelvic movements on a Swiss ball during labour reduced the duration of labour, pain intensity, and maternal fatigue and anxiety; they also lowered the risk of caesarean section and vulvar swelling. Several effects exceeded the smallest worthwhile effect.

REGISTRATION

NCT04124835.

Evolution of vertebral numbers in primates, with a focus on hominoids and the last common ancestor of hominins and panins

The primate vertebral column has been extensively studied, with a particular focus on hominoid primates and the last common ancestor of humans and chimpanzees. The number of vertebrae in hominoids-up to and including the last common ancestor of humans and chimpanzees-is subject to considerable debate. However, few formal ancestral state reconstructions exist, and none include a broad sample of primates or account for the correlated evolution of the vertebral column. Here, we conduct an ancestral state reconstruction using a model of evolution that accounts for both homeotic (changes of one type of vertebra to another) and meristic (addition or loss of a vertebra) changes. Our results suggest that ancestral primates were characterized by 29 precaudal vertebrae, with the most common formula being seven cervical, 13 thoracic, six lumbar, and three sacral vertebrae. Extant hominoids evolved tail loss and a reduced lumbar column via sacralization (homeotic transition at the last lumbar vertebra). Our results also indicate that the ancestral hylobatid had seven cervical, 13 thoracic, five lumbar, and four sacral vertebrae, and the ancestral hominid had seven cervical, 13 thoracic, four lumbar, and five sacral vertebrae. The last common ancestor of humans and chimpanzees likely either retained this ancestral hominid formula or was characterized by an additional sacral vertebra, possibly acquired through a homeotic shift at the sacrococcygeal border. Our results support the 'short-back' model of hominin vertebral evolution, which postulates that hominins evolved from an ancestor with an African ape-like numerical composition of the vertebral column.

The squirrel is in the detail: Anatomy and morphometry of the tail in Sciuromorpha (Rodentia, Mammalia)

In mammals, the caudal vertebrae are certainly among the least studied elements of their skeleton. However, the tail plays an important role in locomotion (e.g., balance, prehensility) and behavior (e.g., signaling). Previous studies largely focused on prehensile tails in Primates and Carnivora, in which certain osteological features were selected and used to define tail regions (proximal, transitional, distal). Interestingly, the distribution pattern of these anatomical characters and the relative proportions of the tail regions were similar in both orders. In order to test if such tail regionalization can be applied to Rodentia, we investigated the caudal vertebrae of 20 Sciuridae and six Gliridae species. Furthermore, we examined relationships between tail anatomy/morphometry and locomotion. The position of selected characters along the tail was recorded and their distribution was compared statistically using Spearman rank correlation. Vertebral body length (VBL) was measured to calculate the proportions of each tail region and to perform procrustes analysis on the shape of relative vertebral body length (rVBL) progressions. Our results show that tail regionalization, as defined for Primates and Carnivora, can be applied to almost all investigated squirrels, regardless of their locomotor category. Moreover, major locomotor categories can be distinguished by rVBL progression and tail region proportions. In particular, the small flying squirrels Glaucomys volans and Hylopetes sagitta show an extremely short transitional region. Likewise, several semifossorial taxa can be distinguished by their short distal region. Moreover, among flying squirrels, Petaurista petaurista shows differences with the small flying squirrels, mirroring previous observations on locomotory adaptations based on their inner ear morphometry. Our results show furthermore that the tail region proportions of P. petaurista, phylogenetically more basal than the small flying squirrels, are similar to those of bauplan-conservative arboreal squirrels.

Developmental origins of variability in pelvic dimensions: Evidence from nulliparous South Asian women in the United Kingdom

OBJECTIVES

Pelvic growth may be sensitive to early-life nutrition, with implications for maternal risk of obstructed labor. However, the "developmental origins" of adult pelvic variability require further investigation. We tested whether adult pelvic dimensions are associated with two components of height, indexing different periods of linear growth: tibia length, a proxy for early postnatal growth, and height-residual (height regressed on tibia length), a proxy for later growth. We also tested whether adult pelvic dimensions are associated with birth weight, a marker of nutritional investment in utero.

METHODS

In this cross-sectional study, data were obtained on 68 nulliparous young women of South Asian ancestry. Pelvic dimensions (bi-iliac and bi-acetabular breadth, anteroposterior pelvic inlet and outlet, interspinous and intertuberous diameter) were measured using magnetic resonance imaging. Height and tibia length were measured manually. Birth weight and gestational age were obtained by recall. Multivariable regression models were fitted with a given pelvic dimension regressed on height-residual, tibia, and birth weight, with the latter adjusted for gestational age.

RESULTS

Controlling for birth weight, height-residual was predictive of bi-acetabular breadth, bi-iliac breadth, and the pelvic inlet, while tibia length significantly predicted all dimensions except interspinous diameter. Controlling for the linear growth variables, birth weight was predictive of bi-iliac breadth only.

CONCLUSIONS

Markers of linear growth during both early and later development were associated with adult pelvic dimensions, whereas size at birth was poorly predictive. Efforts to reduce stunting in early life may facilitate the attainment of maximum potential growth for both height and the pelvis.

Proximate cause, anatomical correlates, and obstetrical implication of a supernumerary lumbar vertebra in humans

OBJECTIVES

Three issues are considered on variation in number of presacral vertebrae (PSV) in humans: (1) sexual difference in number of PSV, (2) inactivation of Hoxd-11 gene as etiology for a supernumerary lumbar vertebra, and (3) anatomical correlates of a supernumerary lumbar vertebra, including lumbar-sacral nearthrosis, and pelvic size.

MATERIALS AND METHODS

Sample was 407 skeletonized females and 1,318 males from United States; ages at death were 20 to 49 years. Two subsamples of males were used: (1) 98 with modal numbers of cervical, thoracic, lumbar, and sacral vertebrae (PSV = 24) and (2) 45 with a supernumerary lumbar vertebra but modal numbers for other vertebral segments (PSV = 25). Measurements were taken of ulna, second metacarpal, vertebrae, femur, and pelvis; presence of lumbar-sacral nearthrosis was observed.

RESULTS

Although 90% of females and males have 24 PSV, females have higher frequency of 23 PSV and males have higher frequency of 25 PSV. Compared to males with 24 PSV, males with 25 PSV and supernumerary lumbar vertebra show (1) no difference in anatomies associated with inactivation of Hoxd-11, and (2) higher frequency of lumbar-sacral nearthrosis and smaller pelvic inlet circumference.

DISCUSSION

Sexual difference in number of PSV may be due to tempo of somite formation and Hox gene activation. Hypothesis is not supported that a supernumerary lumbar vertebra is due to inactivation of Hoxd-11. The presence of a supernumerary lumbar vertebra is associated with small pelvic inlet circumference, which can be obstetrically disadvantageous.

Evolution of the Human Pelvis

No bone in the human postcranial skeleton differs more dramatically from its match in an ape skeleton than the pelvis. Humans have evolved a specialized pelvis, well-adapted for the rigors of bipedal locomotion. Precisely how this happened has been the subject of great interest and contention in the paleoanthropological literature. In part, this is because of the fragility of the pelvis and its resulting rarity in the human fossil record. However, new discoveries from Miocene hominoids and Plio-Pleistocene hominins have reenergized debates about human pelvic evolution and shed new light on the competing roles of bipedal locomotion and obstetrics in shaping pelvic anatomy. In this issue, 13 papers address the evolution of the human pelvis. Here, we summarize these new contributions to our understanding of pelvic evolution, and share our own thoughts on the progress the field has made, and the questions that still remain. Anat Rec, 300:789-797, 2017. © 2017 Wiley Periodicals, Inc.