The ontogeny of occipital bone convexity in a longitudinal sample of extant humans
Notice bibliographique
Résumé
The occipital bun, a distinctive convexity of the occipital squama, is often considered to be a uniquely derived Neandertal trait. Some scholars, however, consider the occipital morphology found in some early modern and extant human crania (often described as “hemi-buns”) to be homologous with Neandertal occipital buns. A number of hypotheses have been proposed to explain occipital bun/hemi-bun development, including neck muscle function, head carriage, brain growth timing, and cranial base cartilage growth timing, as well as braincase and facial integration. The feature, however, has never before been metrically quantified in a large subadult sample or studied in a well-documented growth series. The primary goal of this dissertation, therefore, was to assess hemi-bun growth and development in a combined comparative sample of extant humans amassed from the following growth series: the University of Toronto Burlington Growth Study, the Iowa Facial Growth Study, the Oregon Growth Study, the University of Oklahoma Denver Growth Study, the Wright State University Fels Longitudinal Study, and the Michigan Growth Study.\nCephalograms from these studies facilitated the collection of longitudinal cranial growth and development data. In total, measurements were collected from 468 cephalograms representing 16 males and 10 females. Measured subjects represented the ends of the range of variation in adult midsagittal occipital bone shape, including subjects with defined hemi-buns, as well as subjects lacking all evidence of hemi-bun morphology. Frontal and lateral cephalograms were measured for each subject at 9 age points, spanning from 3.0 to 20.4 years of age. A total of 16 landmarks and 153 sliding semi-landmarks were digitized at each age point. Geometric morphometric analyses, including relative warps analysis and two-block partial least squares analysis, were conducted to assess patterns of cranial covariation and sexual dimorphism in occipital bone growth and possible attendant variation in occipital bun development or absence.\nIn both bunned and non-bunned subjects, midsagittal occipital shape was found to be established very early in ontogeny, and then to remain largely unchanged between 3 years of age and adulthood. This result contradicts previous developmental hypotheses, which posit that occipital bunning results from a pattern of late posteriorly-directed brain growth. No evidence of sexual dimorphism in hemi-bun shape was found to exist in this extant human sample; however, defined hemi-buns were found to covary significantly with an elongated and low midsagittal neurocranial vault in both sexes. Other aspects of cranial morphology, including cranial and basicranial breadth, midcoronal vault shape, and basicranial angle, did not covary significantly with occipital bun morphology at any of the sampled age points.\nThese results reveal that occipital bunning, at least in this sample, is not a discrete trait, but instead develops along a continuum in association with a distinct pattern of neurocranial elongation. Previous studies have suggested that Neandertal occipital buns are similarly associated with elongated cranial vaults. While more work must be done to quantify occipital bun morphology in fossil subadults, this study finds no evidence to disprove the developmental homology of the feature in modern humans and Neandertals, and therefore further undermines the idea that occipital bunning is a unique Neandertal trait.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,002 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».