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This research was funded by the Spanish Ministry of Economy and Competitivity (no. CGL 2015-63648-P) to M.B. D.G.-M. was funded by IdEx University of Bordeaux Investments for the Future programme (no. ANR-10-IDEX-03-02) and the European Commission’s Research Infrastructure Action via the Synthesys Projects (nos. SE-TAF-6406, DE-TAF-6404, BE-TAF-5639). Financial support for M.H. was provided by the Swiss National Science Foundation (no. 31003A_176319/1) and the Mäxi Foundation. A.G.-O. received support from the Spanish FEDER/Ministerio de Ciencia e Innovación-AEI (project no. PGC2018-093925-B-C33) and Research Group (no. IT1418-19) from Eusko Jaurlaritza-Gobierno Vasco. A.G.-O. is funded by a Ramón y Cajal fellowship (no. RYC-2017-22558)., The tall and narrow body shape of anatomically modern humans (Homo sapiens) evolved via changes in the thorax, pelvis and limbs. It is debated, however, whether these modifications first evolved together in African Homo erectus, or whether H. erectus had a more primitive body shape that was distinct from both the more ape-like Australopithecus species and H. sapiens. Here we present the first quantitative three-dimensional reconstruction of the thorax of the juvenile H. erectus skeleton, KNM-WT 15000, from Nariokotome, Kenya, along with its estimated adult rib cage, for comparison with H. sapiens and the Kebara 2 Neanderthal. Our three-dimensional reconstruction demonstrates a short, mediolaterally wide and anteroposteriorly deep thorax in KNM-WT 15000 that differs considerably from the much shallower thorax of H. sapiens, pointing to a recent evolutionary origin of fully modern human body shape. The large respiratory capacity of KNM-WT 15000 is compatible with the relatively stocky, more primitive, body shape of H. erectus., Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

Objectives The human respiratory apparatus is characterized by sexual dimorphism, the cranial airways of males being larger (both absolutely and relatively) than those of females. These differences have been linked to sex-specific differences in body composition, bioenergetics, and respiratory function. However, whether morpho-functional variation in the thorax is also related to these features is less clear. We apply 3D geometric morphometrics to study these issues and their implications for respiratory function. Material and methods Four hundred two landmarks and semilandmarks were measured in CT-reconstructions of rib cages from adult healthy subjects (Nmale = 18; Nfemale = 24) in maximal inspiration (MI) and maximal expiration (ME). After Procrustes registration, size and shape data were analyzed by mean comparisons and regression analysis. Respiratory function was quantified through functional size, which is defined as the difference of rib cage size between MI and ME. Results Males showed significantly larger thorax size (p < .01) and functional size (p < .05) than females. In addition, the 3D-shape differed significantly between sexes (p < .01). Male rib cages were wider (particularly caudally) and shorter, with more horizontally oriented ribs when compared to females. While thorax widening and rib orientation were unrelated to allometry, thorax shortening showed a slight allometric signal. Conclusions Our findings are in line with previous research on sexual dimorphism of the respiratory system. However, we add that thorax shortening observed previously in males is the only feature caused by allometry. The more horizontally oriented ribs and the wider thorax of males may indicate a greater diaphragmatic contribution to rib cage kinematics than in females, and differences in functional size fit with the need for greater oxygen intake in males., Objetivos El aparato respiratorio humano se caracteriza por un dimorfismo sexual, siendo las vías respiratorias craneales de los machos más grandes (tanto absoluta como relativamente) que las de las hembras. Estas diferencias se han relacionado con diferencias específicas de cada sexo en la composición corporal, la bioenergética y la función respiratoria. Sin embargo, no está tan claro si la variación morfofuncional en el tórax también está relacionada con estas características. Aplicamos morfometría geométrica 3D para estudiar estas cuestiones y sus implicaciones para la función respiratoria. Material y métodos Se midieron cuatrocientos dos puntos de referencia y semipuntos de referencia en reconstrucciones por TC de cajas torácicas de sujetos adultos sanos (Nmale = 18; Nfemale = 24) en inspiración máxima (IM) y espiración máxima (EM). Después del registro de Procrustes, los datos de tamaño y forma se analizaron mediante comparaciones de medias y análisis de regresión. La función respiratoria se cuantificó a través del tamaño funcional, que se define como la diferencia del tamaño de la caja torácica entre IM y EM. Resultados Los machos mostraron un tamaño de tórax significativamente mayor (p <0.01) y un tamaño funcional (p <0.05) que las hembras. Además, la forma 3D difirió significativamente entre sexos (p < 0.01). Las cajas torácicas de los machos eran más anchas (particularmente caudalmente) y más cortas, con costillas más orientadas horizontalmente en comparación con las de las hembras. Mientras que el ensanchamiento del tórax y la orientación de las costillas no estaban relacionados con la alometría, el acortamiento del tórax mostró una ligera señal alométrica. Conclusiones Nuestros hallazgos están en línea con investigaciones previas sobre el dimorfismo sexual del sistema respiratorio. Sin embargo, agregamos que el acortamiento del tórax observado previamente en los machos es la única característica causada por la alometría. Las costillas más orientadas horiz, Ministerio de Economía y Competitividad (MINECO), Leakey Foundation, Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

This research was funded by the Spanish Ministry of Economy and Competitiveness (CGL2012-37279, MINECO), the Leakey Foundation, and PI10/02089 ( Fondo de Investigación Sanitaria) Ministry of Health, Spain., Chest size is important for reconstructing Neandertal paleobiology. The large size of the Neandertal skeletal thorax has been interpreted about cold adaptation, increased body mass, specific body shape, and increased activity levels (Franciscus and Churchill, 2002, Churchill, 2006, Gómez-Olivencia et al., 2009). Large Neandertal chests should also be expected because chest and lung sizes are correlated developmentally (Thurlbeck, 1982, Bastir et al., 2013a), because lung size scales isometrically with body mass across mammals (Stahl, 1967), and because body mass was larger in Neandertals than in modern humans (Ruff et al., 1997, Froehle and Churchill, 2009). The notion of large chests has recently been reinforced by Gómez-Olivencia et al. (2009), who measured the ribs of the Kebara 2 Neandertal male using arc lengths. Their study suggested that the upper ribs of Kebara 2 are within the range of modern humans, and the middle (ribs 4, 5, 7) and lower (ribs 8, 10) thoracic ribs exceed the range of modern human variation. Consequently, this predicts that the total thorax size (the sum of the sizes of each of the ribs) should be larger in Kebara than in modern humans. However, Gómez-Olivencia et al. (2009) also identified a problem in the original reconstruction of the 6th and 7th ribs of Kebara due to a misidentification of fragments fitted together by Arensburg (1991), who stated that the ribs of “Kebara man are quite similar in metric and morphological respects to those of ribs in present human populations” (Arensburg, 1991: 142). Nevertheless, misidentifications such as those identified by Gómez Olivencia et al. (2009) could affect size assessments. Bastir et al. (2012) measured the reconstruction of the Kebara rib cage (Sawyer and Maley, 2005) using 3D geometric morphometrics, and no evidence for such enlarged chest size was found, supporting Arensburg's (1991) opinion. Thus, the size of one of the best-preserved Neandertal male thoracic skeletons is currently uncle, Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

SCOPUS: ar.j, info:eu-repo/semantics/published

Rib internal anatomy and its cross-sectional morphology inform about important biomechanical or even evolutionary aspects. Classic histological studies require destructive techniques that are reprehensible depending on the case (e.g., fossils). In the last years, non-destructive CT-based methods are contributing to complementing previous knowledge without damaging the bone. Even though these methods have been proved to be useful to understand adult variation, we do not know whether these methods are useful to cover ontogenetic variation. This work compares classical histological methods with medical- and micro-CT to quantify the amount of mineral area at the rib midshaft (% Min. Ar.), a proxy for bone density. We compared cross-sections from an ontogenetic sample of 14 human first ribs ranging from perinates to adults using a) classical histology, b) HD (9–17 microns) and SD micro-CT (90 microns), and c) standard medical-CT (0.66 mm). We found that all the CT-based methods provide a larger % Min. Ar. compared to the histological techniques, but the HD micro-CT resolution is the only capable of producing results comparable to classical histology (p > 0.01), with the SD micro-CT and the medical-CT producing statistically larger results compared to classical histology (p < 0.01). In addition, it is important to state that the resolution of a standard medical-CT is not high enough to differentiate between mineral and non-mineral areas of the cross-sections for perinates and infants. These results could have important implications to avoid (when necessary) destructive techniques that are not appropriate in the case of highly valuable specimens such as fossils.

The tall and narrow body shape of anatomically modern humans (Homo sapiens) evolved via changes in the thorax, pelvis and limbs. It is debated, however, whether these modifications first evolved together in African Homo erectus, or whether H. erectus had a more primitive body shape that was distinct from both the more ape-like Australopithecus species and H. sapiens. Here we present the first quantitative three-dimensional reconstruction of the thorax of the juvenile H. erectus skeleton, KNM-WT 15000, from Nariokotome, Kenya, along with its estimated adult rib cage, for comparison with H. sapiens and the Kebara 2 Neanderthal. Our three-dimensional reconstruction demonstrates a short, mediolaterally wide and anteroposteriorly deep thorax in KNM-WT 15000 that differs considerably from the much shallower thorax of H. sapiens, pointing to a recent evolutionary origin of fully modern human body shape. The large respiratory capacity of KNM-WT 15000 is compatible with the relatively stocky, more primitive, body shape of H. erectus.

Sexual dimorphism is an important feature of adult thorax morphology, but when and how sex-related differences in the ribcage arise during ontogeny is poorly known. Previous research proposed that sex-related size differences in the nasal region arise during puberty. Therefore, we explore whether ribcage sexual dimorphism also arises at that time and whether this sexual dimorphism is maintained until old age. We measured 526 (semi)landmarks on 80 CT-based human ribcage reconstructions, on individuals ranging from 7 to 65 year-old. The 3D coordinates were submitted to the Procrustes superimposition and analyzed. Our results show that the trajectories of thorax size and shape between sexes diverge at around 12 years of age, and continue slightly diverging until old age. The differential ontogenetic trends cause adult male ribcages to become deeper, shorter, and wider than female. Our results are consistent with the evidence from the cranial respiratory system, with the development of sexual dimorphism probably related to changes in body composition during puberty combined with changes in the reproductive system.

The aim of the present study was to test the hypothesis that ribs shape changes in patients with OI are more relevant for respiratory function than thoracic spine shape. We used 3D geometric morphometrics to quantify rib cage morphology in OI patients and controls, and to investigate its relationship with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1), expressed as absolute value and as percentage of predicted value (% pred). Regression analyses on the full sample showed a significant relation between rib shape and FEV1, FVC and FVC % pred whereas thoracic spine shape was not related to any parameter. Subsequent regression analyses on OI patients confirmed significant relations between dynamic lung volumes and rib shape changes. Lower FVC and FEV1 values are identified in OI patients that present more horizontally aligned ribs, a greater antero-posterior depth due to extreme transverse curve at rib angles and a strong spine invagination, greater asymmetry, and a vertically short, thoraco-lumbar spine, which is relatively straight in at levels 1–8 and shows a marked kyphosis in the thoraco-lumbar transition. Our research seems to support that ribs shape is more relevant for ventilator mechanics in OI patients than the spine shape.

[Objectives]: Sexual dimorphism is an important biological factor underlying morphological variation in the human skeleton. Previous research found sex-related differences in the static ribcage, with males having more horizontally oriented ribs and a wider lower ribcage than females. Furthermore, a recent study found sex-related differences in the kinematics of the human lungs, with cranio-caudal movements of the caudal part of the lungs accounting for most of the differences between sexes. However, these movements cannot be quantified in the skeletal ribcage, so we do not know if the differences observed in the lungs are also reflected in sex differences in the motion of the skeletal thorax., [Materials and methods]: To address this issue, we quantified the morphological variation of 42 contemporary human ribcages (sex-balanced) in both maximal inspiration and expiration using 526 landmarks and semilandmarks. Thoracic centroid size differences between sexes were assessed using a t test, and shape differences were assessed using Procrustes shape coordinates, through mean comparisons and dummy regressions of shape on kinematic status. A principal components analysis was used to explore the full range of morphological variation., [Results]: Our results show significant size differences between males and females both in inspiration and expiration (p <.01) as well as significant shape differences, with males deforming more than females during inspiration, especially in the mediolateral dimension of the lower ribcage. Finally, dummy regressions of shape on kinematic status showed a small but statistically significant difference in vectors of breathing kinematics between males and females (14.78°; p <.01). [Discussion]: We support that sex-related differences in skeletal ribcage kinematics are discernible, even when soft tissues are not analyzed. We hypothesize that this differential breathing pattern is primarily a result of more pronounced diaphragmatic breathing in males, which might relate to differences in body composition, metabolism, and ultimately greater oxygen demand in males compared to females. Future research should further explore the links between ribcage morphological variation and basal metabolic rate.

Our most recent fossil relatives, the Neanderthals, had a large brain and a very heavy body compared to modern humans. This type of body requires high levels of energetic intake. While food (meat and fat consumption) is a source of energy, oxygen via respiration is also necessary for metabolism. We would therefore expect Neanderthals to have large respiratory capacities. Here we estimate the pulmonary capacities of Neanderthals, based on costal measurements and physiological data from a modern human comparative sample. The Kebara 2 male had a lung volume of about 9.04 l; Tabun C1, a female individual, a lung volume of 5.85 l; and a Neanderthal from the El Sidrón site, a lung volume of 9.03 l. These volumes are approximately 20% greater than the corresponding volumes of modern humans of the same body size and sex. These results show that the Neanderthal body was highly sensitive to energy supply.

Sexual dimorphism in the human respiratory system has been previously reported at the skeletal (cranial and thoracic) level, but also at the pulmonary level. Regarding lungs, foregoing studies have yielded sex‐related differences in pulmonary size as well as lung shape details, but different methodological approaches have led to discrepant results on differences in respiratory patterns between males and females. The purpose of this study is to analyse sexual dimorphism in human lungs during forced respiration using 3D geometric morphometrics. Eighty computed tomographies (19 males and 21 females) were taken in maximal forced inspiration (FI) and expiration (FE), and 415 (semi)landmarks were digitized on 80 virtual lung models for the 3D quantification of pulmonary size, shape and kinematic differences. We found that males showed larger lungs than females (P < 0.05), and significantly greater size and shape differences between FI and FE. Morphologically, males have pyramidal lung geometry, with greater lower lung width when comparing with the apices, in contrast to the prismatic lung shape and similar widths at upper and lower lungs of females. Multivariate regression analyses confirmed the effect of sex on lung size (36.26%; P < 0.05) and on lung shape (7.23%; P < 0.05), and yielded two kinematic vectors with a small but statistically significant angle between them (13.22°; P < 0.05) that confirms sex‐related differences in the respiratory patterns. Our 3D approach shows sexual dimorphism in human lungs likely due to a greater diaphragmatic action in males and a predominant intercostal muscle action in females during breathing. These size and shape differences would lead to different respiratory patterns between sexes, whose physiological implications need to be studied in future research.

The human ribcage expands and contracts during respiration as a result of the interaction between the morphology of the ribs, the costo-vertebral articulations and respiratory muscles. Variations in these factors are said to produce differences in the kinematics of the upper thorax and the lower thorax, but the extent and nature of any such differences and their functional implications have not yet been quantified. Applying geometric morphometrics we measured 402 three-dimensional (3D) landmarks and semilandmarks of 3D models built from computed tomographic scans of thoraces of 20 healthy adult subjects in maximal forced inspiration (FI) and expiration (FE). We addressed the hypothesis that upper and lower parts of the ribcage differ in kinematics and compared different models of functional compartmentalization. During inspiration the thorax superior to the level of the sixth ribs undergoes antero-posterior expansion that differs significantly from the medio-lateral expansion characteristic of the thorax below this level. This supports previous suggestions for dividing the thorax into a pulmonary and diaphragmatic part. While both compartments differed significantly in mean size and shape during FE and FI the size changes in the lower compartment were significantly larger. Additionally, for the same degree of kinematic shape change, the pulmonary thorax changes less in size than the diaphragmatic thorax. Therefore, variations in the form and function of the diaphragmatic thorax will have a strong impact on respiratory function. This has important implications for interpreting differences in thorax shape in terms of respiratory functional differences within and among recent humans and fossil hominins. Anat Rec, 300:255–264, 2017. © 2016 Wiley Periodicals, Inc.

Ever since the seminal papers of Keith and Schultz, hominoid primate ribcages have been described as either “funnel-” or “barrel-shaped.” Following this dichotomic typology, it is currently held that Homo sapiens and hylobatids (gibbons and siamangs) share a barrel-shaped ribcage and that they are more similar to each other than to the funnel-shaped thoraces of great apes (Gorilla, Pan, and Pongo). Other researchers hypothesized that thoracic width and the invagination of the thoracic spine into the thorax are related to allometry. However, analyses that take into account the complex three-dimensional (3D) shape of the ribcage are lacking. Here, we address hypotheses about thorax shape and evolution using 3D morphometrics of thoraces in anatomical connection obtained by computed tomography scans of 23 hominoid cadavers and 10 humans and examining thorax compartments composed of seven ribs (1–7 thorax) and of 11 ribs (1–11 thorax). In the 1–7 thorax analyses, the human thorax is uniquely flat because of torsion of the upper and central ribs, differing from all non-human hominoids including hylobatids. In the 1–11 thorax analyses, humans are markedly different from African great apes, with hylobatids and orangutans intermediate. In full shape space analyses, affinities between orangutans and humans on the one hand and between hylobatids and African great apes on the other are evident. Therefore, we reject the hypothesis that humans and hylobatids bear any special affinities in overall 3D thorax shape to each other. We find that larger thoraces are wider and flatter, with a more invaginated spine, supporting the allometric hypothesis. Hominoid thorax variation shows complex interactions between allometry, rib curves, torsion, and declination, and the morphology of the costo-vertebral joint and the thoracic vertebral column. When considering functional specializations alongside phylogenetic relationships, an overly simplistic dichotomy between funnel-shaped and barrel-s

Objectives: The human respiratory apparatus is characterized by sexual dimorphism, the cranial airways of males being larger (both absolutely and relatively) than those of females. These differences have been linked to sex-specific differences in body composition, bioenergetics, and respiratory function. However, whether morpho-functional variation in the thorax is also related to these features is less clear. We apply 3D geometric morphometrics to study these issues and their implications for respiratory function. Material and methods: Four hundred two landmarks and semilandmarks were measured in CT-reconstructions of rib cages from adult healthy subjects (N = 18; N = 24) in maximal inspiration (MI) and maximal expiration (ME). After Procrustes registration, size and shape data were analyzed by mean comparisons and regression analysis. Respiratory function was quantified through functional size, which is defined as the difference of rib cage size between MI and ME. Results: Males showed significantly larger thorax size (p <.01) and functional size (p <.05) than females. In addition, the 3D-shape differed significantly between sexes (p <.01). Male rib cages were wider (particularly caudally) and shorter, with more horizontally oriented ribs when compared to females. While thorax widening and rib orientation were unrelated to allometry, thorax shortening showed a slight allometric signal. Conclusions: Our findings are in line with previous research on sexual dimorphism of the respiratory system. However, we add that thorax shortening observed previously in males is the only feature caused by allometry. The more horizontally oriented ribs and the wider thorax of males may indicate a greater diaphragmatic contribution to rib cage kinematics than in females, and differences in functional size fit with the need for greater oxygen intake in males.

Despite the importance of the thorax for human biology, its 3D morphological variability associated to eco-geographical variation is poorly understood. Allen´s and bergmann´s eco-geographic rules link body size and shape to climate conditions in homoeothermic mammals.