Sexual dimorphism in the vertebral wedging of the human lumbar vertebrae and its importance as a comparative framework for understanding the wedging pattern of Neanderthals

García‐Martínez, Daniel; Martelli, S.; Torres-Tamayo, Nicole; Jiménez‐Arenas, Juan Manuel; Martín, Armando González; Campo, Manuel Domingo D'Angelo del; Cambra‐Moo, Óscar; Lois-Zlolniski, Stephanie; Nalla, Shahed; Sanchis‐Gimeno, Juan A.; Bastir, Markus

doi:10.1016/j.quaint.2020.05.054

Cited by 9 publications

(12 citation statements)

References 68 publications

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“…Yet, the most recent reconstruction of the La Chapelle aux Saints Neandertal suggests vertebral curvatures similar to modern humans 14 and this indicates that a better fossil documentation of lumbar spine anatomy in Neandertals is needed. Importantly, a recent study accounting for a wide range of population variability in modern humans, identified consistently and significantly more pronounced lordotic wedging in Neandertal L5 of Kebara 2, Shanidar 3, and La Chapelle aux Saints 41 together with a more hypo-lordotic wedging in upper lumbar vertebra. Accordingly, this could suggest a completely different position of the lumbar spine within the trunk, with yet unclear biomechanical implications.…”

Section: Discussionmentioning

confidence: 97%

“…Lumbar lordosis varies considerably in human populations 12,[39][40][41] and affects locomotor capacities. It has been shown that greater lordosis facilitates shock absorption, for example, when running 34 , while weaker lordosis produces a more forwards orientation of the pelvis, which is beneficial for leg return during sprinting 31 .…”

Section: Evolutionary Anatomical Changesmentioning

confidence: 99%

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Variation in human 3D trunk shape and its functional implications in hominin evolution

Bastir

Ruiz

Rueda

et al. 2022

Sci Rep

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This study investigates the contribution of external trunk morphology and posture to running performance in an evolutionary framework. It has been proposed that the evolution from primitive to derived features of torso shape involved changes from a mediolaterally wider into a narrower, and antero-posteriorly deeper into a shallower, more lightly built external trunk configuration, possibly in relation to habitat-related changes in locomotor and running behaviour. In this context we produced experimental data to address the hypothesis that medio-laterally narrow and antero-posteriorly shallow torso morphologies favour endurance running capacities. We used 3D geometric morphometrics to relate external 3D trunk shape of trained, young male volunteers (N = 27) to variation in running velocities during different workloads determined at 45–50%, 70% and 85% of heart rate reserve (HRR) and maximum velocity. Below 85% HRR no relationship existed between torso shape and running velocity. However, at 85% HRR and, more clearly, at maximum velocity, we found highly statistically significant relations between external torso shape and running performance. Among all trained subjects those with a relatively narrow, flat torso, a small thoracic kyphosis and a more pronounced lumbar lordosis achieved significantly higher running velocities. These results support the hypothesis that external trunk morphology relates to running performance. Low thoracic kyphosis with a flatter ribcage may affect positively respiratory biomechanics, while increased lordosis affects trunk posture and may be beneficial for lower limb biomechanics related to leg return. Assuming that running workload at 45–50% HRR occurs within aerobic metabolism, our results may imply that external torso shape is unrelated to the evolution of endurance running performance.

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Section: Discussionmentioning

confidence: 97%

Section: Evolutionary Anatomical Changesmentioning

confidence: 99%

Variation in human 3D trunk shape and its functional implications in hominin evolution

Bastir

Ruiz

Rueda

et al. 2022

Sci Rep

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show abstract

“…These spinopelvic relationships also shed light on the human sex differences in lumbar lordosis and vertebral wedging, which tend to be greater in females than in males 47,52,53 . Whitcome et al 47 proposed that this dimorphism, which was already present in early Homo and partly even in Australopithecus, evolved as an adaptation to mitigate the shearing forces generated by foetal load.…”

Section: Discussionmentioning

confidence: 88%

The evolution of pelvic canal shape and rotational birth in humans

Stansfield

Fischer

Mitterœcker

2021

Preprint

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The human foetus needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part, or outlet, of the birth canal has a pronounced anteroposteriorly oval shape. Here we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability. This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that upright stance limits the anteroposterior dimension of the inlet. A deeper inlet requires greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements on the pelvic inlet and outlet have led to the complex shape of the human pelvic canal and to the evolution of rotational birth.

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“…These spinopelvic relationships also shed light on the human sex differences in lumbar lordosis and vertebral wedging, which tend to be greater in females than in males [ 58 , 74 , 75 ]. Whitcome et al [ 58 ] proposed that this dimorphism, which was already present in early Homo and partly even in Australopithecus , evolved as an adaptation to mitigate the shearing forces generated by foetal load.…”

Section: Discussionmentioning

confidence: 99%

The evolution of pelvic canal shape and rotational birth in humans

et al. 2021

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Background The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pronounced anteroposteriorly oval shape. Results Here, we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist the pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress, and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability. Conclusions This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that the mediolateral elongation has evolved because of the limits on the anteroposterior diameter imposed by upright posture. We show that an anteroposteriorly deeper inlet would require greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements of the pelvic inlet and outlet likely have led to the complex shape of the pelvic canal and to the evolution of rotational birth characteristic of humans.

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Sexual dimorphism in the vertebral wedging of the human lumbar vertebrae and its importance as a comparative framework for understanding the wedging pattern of Neanderthals

Cited by 9 publications

References 68 publications

Variation in human 3D trunk shape and its functional implications in hominin evolution

Variation in human 3D trunk shape and its functional implications in hominin evolution

The evolution of pelvic canal shape and rotational birth in humans

The evolution of pelvic canal shape and rotational birth in humans

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