Post by Admin on Oct 9, 2020 21:31:37 GMT
RESULTS
Final reconstructions of the four Neanderthal ribcages are shown in Fig. 1 and text S1.
Fig. 1 Final virtual reconstruction of the four Neanderthal individuals studied here.
Bones that are preserved in the original specimen are shown in red, whereas mirror images are shown in blue and statistical estimations in gray (only for D1 specimen).
MH and Neanderthal thorax size and growth patterns during early postnatal ontogeny
The ribcage of MH shows a rapid growth during the first ca. 100 days of life, which changes to a slower growth rate afterward (Fig. 2). For Neanderthals, we measured the centroid size (CS; see Materials and Methods) directly from the thorax reconstruction in D1 and using the costal size and thorax CS correlation (double-checked in the latter 3D reconstruction) in the rest of the individuals (Table 1 and text S1). When plotted with respect to their estimated age (or age ranges), the perinatal M1 individual fits well within MH size variation; the infant D1 is within this variation but above the MH regression line. For the two other Neanderthals, their current age-at-death ranges are wide but consistent with growth patterns observed for M1 and D1. The growth trajectory based on the mean Neanderthal age-at-death estimates roughly overlaps with that of MH during the first ca. 100 days but then diverges, with the Neanderthals’ growth being slightly faster. This overall pattern, using CS as a proxy for thoracic size, is also present on the tubercle-ventral chord (TVC) of individual ribs (text S2), a classic measurement for evaluating costal size (22, 25).
Fig. 2 Logarithmic growth trajectories for MH [y = 136.81ln(x) + 709.07; r2 = 0.86] and Neanderthals.
For the latter, we plotted minimum (triangles), average (squares), and maximum (circles) ages proposed in the literature. The growth trajectories of MH and Neanderthals are displayed in blue and red color, respectively, and Neanderthal trajectories representing minimum and maximum ages are displayed as dotted lines. Note that individuals with very similar CS are overlapped, e.g., the case of Ind27 and Ind29.
When compared to MH of the same CS (as a proxy of volume), the four Neanderthal reconstructions showed metric differences that were consistent in all of them regardless of their age at death (text S3). All the Neanderthals had a craniocaudally shorter thoracic spine and a deeper thorax anterior-posteriorly when compared to MH of equivalent CS. However, the thorax width of the Neanderthals exceeded that of MH only in the oldest individuals (D1 and RdM), but not in the youngest ones (M1 and LM2; Table 2 and text S3).
Table 2 Selected metric measurements (in millimeters) in the 3D reconstructed ribcages of fossil specimens compared with standardized MHs for the CS of each fossil specimen.
Thorax width was quantified at the level of rib 7, thorax depth is at the level of T5 from the spinous process to the distal end of rib 5 (average of both sides), and anterior spine length is quantified as the distance between the anterior-superior–most point of T1 body and the anterior-inferior–most point of the T12 body. Standardized values of MHs were calculated on the basis of linear regression of classic measurements on full thorax CS (text S4). Smaller Neanderthal values are labeled with the symbol *, whereas larger values are labeled by the symbol #.
Developmental changes in the ribcage during early postnatal ontogeny in MH and Neanderthals
During early postnatal ontogeny, MH changes from a ribcage that is relatively narrow in the cranial part and extremely wide in the caudal part toward a ribcage that is volumetrically expanded in the cranial part and still wide in the caudal part (text S4). Perinatal Neanderthals (M1 and LM2) also have an upper ribcage that is relatively narrower than in older specimens (D1 and RdM), who have a more globular ribcage with similar widths at the upper and lower thorax (Fig. 1). In addition, the exploration of the 3D warps associated with standardized CS in Neanderthals and MH shows consistent interspecific morphological differences throughout the postnatal ontogeny studied here (Fig. 3). The Neanderthal thoracic spine is relatively shorter, and from the third rib onward, the ribcage of the Neanderthals is relatively deeper than in MH. In the most complete individual (D1), it is also possible to observe that its spine is more invaginated within the thorax than in MH (text S5). In this individual, the mid-lower ribs are relatively longer than the uppermost and lowermost ones, when compared to MH of the same CS.
Fig. 3 Neanderthal ribcages (red) compared to MH (blue) of their respective same CS in Procrustes superimposition observed in different views.
To better visualize the morphological differences between species, we warped a complete MH infant thorax 3D model into the coordinates of the fossil specimens using EVAN Toolbox software. Human standardizations were calculated using a multivariate regression of shape on the size of the 29 individuals from the comparative human sample. Perinatal Neanderthals (M1 and LM2) have an upper ribcage that is relatively narrower than in older specimens (D1 and RdM), who have a more globular ribcage, with similar widths at the upper and lower thorax (Fig. 1). Besides, the Neanderthal thoracic spine is relatively shorter, and from the third rib onward, the ribcage of the Neanderthals is relatively deeper than in MH. In the most complete individual (D1), it is possible to observe that this spine is more invaginated into the thorax than in MH. In this individual, it is also possible to assess that, when compared to MH of the same CS, the mid-lower ribs are relatively larger than the uppermost and lowermost ones. Regarding the orientation of the ribs in the sagittal plane, different declination can be observed at different rib levels, with the upper Neanderthal ribs (from 1st to 6th) more declined than in MH and the lower ribs (from 10th to 12th) more horizontally oriented. Rib torsion also contributes to interspecific differences because Neanderthal central ribs (from 6th to 8th) of early individuals have a stronger torsion (understood as spiraling) than in MH.
Regarding the orientation of the ribs in the sagittal plane, a different declination can be observed at different rib levels, with the upper Neanderthal ribs (from 1st to 6th) being more declined than in MH and the lower ribs (from 10th to 12th) more horizontally oriented. Rib torsion also contributes to interspecific differences because Neanderthal central ribs (from 6th to 8th) of early individuals have a stronger torsion (understood as spiraling along the rib axis) than in MH. Last, other minor differences can also be observed in Fig. 3. For example, both the upper (from 1st to 5th) and very lower (from 10th to 12th) regions of the Neanderthal ribcage are slightly wider than in MH, and their first ribs are less curved than in MH (see details in text S5).
Final reconstructions of the four Neanderthal ribcages are shown in Fig. 1 and text S1.
Fig. 1 Final virtual reconstruction of the four Neanderthal individuals studied here.
Bones that are preserved in the original specimen are shown in red, whereas mirror images are shown in blue and statistical estimations in gray (only for D1 specimen).
MH and Neanderthal thorax size and growth patterns during early postnatal ontogeny
The ribcage of MH shows a rapid growth during the first ca. 100 days of life, which changes to a slower growth rate afterward (Fig. 2). For Neanderthals, we measured the centroid size (CS; see Materials and Methods) directly from the thorax reconstruction in D1 and using the costal size and thorax CS correlation (double-checked in the latter 3D reconstruction) in the rest of the individuals (Table 1 and text S1). When plotted with respect to their estimated age (or age ranges), the perinatal M1 individual fits well within MH size variation; the infant D1 is within this variation but above the MH regression line. For the two other Neanderthals, their current age-at-death ranges are wide but consistent with growth patterns observed for M1 and D1. The growth trajectory based on the mean Neanderthal age-at-death estimates roughly overlaps with that of MH during the first ca. 100 days but then diverges, with the Neanderthals’ growth being slightly faster. This overall pattern, using CS as a proxy for thoracic size, is also present on the tubercle-ventral chord (TVC) of individual ribs (text S2), a classic measurement for evaluating costal size (22, 25).
Fig. 2 Logarithmic growth trajectories for MH [y = 136.81ln(x) + 709.07; r2 = 0.86] and Neanderthals.
For the latter, we plotted minimum (triangles), average (squares), and maximum (circles) ages proposed in the literature. The growth trajectories of MH and Neanderthals are displayed in blue and red color, respectively, and Neanderthal trajectories representing minimum and maximum ages are displayed as dotted lines. Note that individuals with very similar CS are overlapped, e.g., the case of Ind27 and Ind29.
When compared to MH of the same CS (as a proxy of volume), the four Neanderthal reconstructions showed metric differences that were consistent in all of them regardless of their age at death (text S3). All the Neanderthals had a craniocaudally shorter thoracic spine and a deeper thorax anterior-posteriorly when compared to MH of equivalent CS. However, the thorax width of the Neanderthals exceeded that of MH only in the oldest individuals (D1 and RdM), but not in the youngest ones (M1 and LM2; Table 2 and text S3).
Table 2 Selected metric measurements (in millimeters) in the 3D reconstructed ribcages of fossil specimens compared with standardized MHs for the CS of each fossil specimen.
Anterior spine
length Thorax depth Thorax width
M1 74.63* 69.17# 86.19*
MH CS = 943.95 79.08 66.81 86.61
LM2 87.82* 81.23# 102.86*
MH
CS = 1115.28 92.94 78.77 103.22
D1 130.46* 120.79# 158.36#
MH
CS = 1675.93 138.29 117.90
Thorax width was quantified at the level of rib 7, thorax depth is at the level of T5 from the spinous process to the distal end of rib 5 (average of both sides), and anterior spine length is quantified as the distance between the anterior-superior–most point of T1 body and the anterior-inferior–most point of the T12 body. Standardized values of MHs were calculated on the basis of linear regression of classic measurements on full thorax CS (text S4). Smaller Neanderthal values are labeled with the symbol *, whereas larger values are labeled by the symbol #.
Developmental changes in the ribcage during early postnatal ontogeny in MH and Neanderthals
During early postnatal ontogeny, MH changes from a ribcage that is relatively narrow in the cranial part and extremely wide in the caudal part toward a ribcage that is volumetrically expanded in the cranial part and still wide in the caudal part (text S4). Perinatal Neanderthals (M1 and LM2) also have an upper ribcage that is relatively narrower than in older specimens (D1 and RdM), who have a more globular ribcage with similar widths at the upper and lower thorax (Fig. 1). In addition, the exploration of the 3D warps associated with standardized CS in Neanderthals and MH shows consistent interspecific morphological differences throughout the postnatal ontogeny studied here (Fig. 3). The Neanderthal thoracic spine is relatively shorter, and from the third rib onward, the ribcage of the Neanderthals is relatively deeper than in MH. In the most complete individual (D1), it is also possible to observe that its spine is more invaginated within the thorax than in MH (text S5). In this individual, the mid-lower ribs are relatively longer than the uppermost and lowermost ones, when compared to MH of the same CS.
Fig. 3 Neanderthal ribcages (red) compared to MH (blue) of their respective same CS in Procrustes superimposition observed in different views.
To better visualize the morphological differences between species, we warped a complete MH infant thorax 3D model into the coordinates of the fossil specimens using EVAN Toolbox software. Human standardizations were calculated using a multivariate regression of shape on the size of the 29 individuals from the comparative human sample. Perinatal Neanderthals (M1 and LM2) have an upper ribcage that is relatively narrower than in older specimens (D1 and RdM), who have a more globular ribcage, with similar widths at the upper and lower thorax (Fig. 1). Besides, the Neanderthal thoracic spine is relatively shorter, and from the third rib onward, the ribcage of the Neanderthals is relatively deeper than in MH. In the most complete individual (D1), it is possible to observe that this spine is more invaginated into the thorax than in MH. In this individual, it is also possible to assess that, when compared to MH of the same CS, the mid-lower ribs are relatively larger than the uppermost and lowermost ones. Regarding the orientation of the ribs in the sagittal plane, different declination can be observed at different rib levels, with the upper Neanderthal ribs (from 1st to 6th) more declined than in MH and the lower ribs (from 10th to 12th) more horizontally oriented. Rib torsion also contributes to interspecific differences because Neanderthal central ribs (from 6th to 8th) of early individuals have a stronger torsion (understood as spiraling) than in MH.
Regarding the orientation of the ribs in the sagittal plane, a different declination can be observed at different rib levels, with the upper Neanderthal ribs (from 1st to 6th) being more declined than in MH and the lower ribs (from 10th to 12th) more horizontally oriented. Rib torsion also contributes to interspecific differences because Neanderthal central ribs (from 6th to 8th) of early individuals have a stronger torsion (understood as spiraling along the rib axis) than in MH. Last, other minor differences can also be observed in Fig. 3. For example, both the upper (from 1st to 5th) and very lower (from 10th to 12th) regions of the Neanderthal ribcage are slightly wider than in MH, and their first ribs are less curved than in MH (see details in text S5).