Evolution of the base of the brain in highly encephalized human species

Bastir, Markus; Rosas, Antonio; Gunz, Philipp; Peña-Melián, Ángel; Manzi, Giorgio; Harvati, Katerina; Kruszynski, Robert; Stringer, Chris; Hublin, Jean‐Jacques

doi:10.1038/ncomms1593

Cited by 155 publications

(118 citation statements)

References 54 publications

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“…Changes in cranial base morphology are thought to be associated with changes in relative brain size (50,51). Hence, distinct differences in middle ear architecture of AMHs and Neandertals may well reflect brain expansion that occurred separately in the two lineages (52,53).…”

Section: Discussionmentioning

confidence: 99%

Morphology and function of Neandertal and modern human ear ossicles

Stoessel

David

Gunz

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The diminutive middle ear ossicles (malleus, incus, stapes) housed in the tympanic cavity of the temporal bone play an important role in audition. The few known ossicles of Neandertals are distinctly different from those of anatomically modern humans (AMHs), despite the close relationship between both human species. Although not mutually exclusive, these differences may affect hearing capacity or could reflect covariation with the surrounding temporal bone. Until now, detailed comparisons were hampered by the small sample of Neandertal ossicles and the unavailability of methods combining analyses of ossicles with surrounding structures. Here, we present an analysis of the largest sample of Neandertal ossicles to date, including many previously unknown specimens, covering a wide geographic and temporal range. Microcomputed tomography scans and 3D geometric morphometrics were used to quantify shape and functional properties of the ossicles and the tympanic cavity and make comparisons with recent and extinct AMHs as well as African apes. We find striking morphological differences between ossicles of AMHs and Neandertals. Ossicles of both Neandertals and AMHs appear derived compared with the inferred ancestral morphology, albeit in different ways. Brain size increase evolved separately in AMHs and Neandertals, leading to differences in the tympanic cavity and, consequently, the shape and spatial configuration of the ossicles. Despite these different evolutionary trajectories, functional properties of the middle ear of AMHs and Neandertals are largely similar. The relevance of these functionally equivalent solutions is likely to conserve a similar auditory sensitivity level inherited from their last common ancestor.middle ear | homo | 3D shape | covariation T he hominin fossil record can only provide indirect information about auditory capacities of our extinct relatives. Inferences about the evolution of the human sense of hearing require understanding of the interplay between form and function in extant species. When auditory capacities are visualized as audiograms, plotting the sensitivity for different frequencies, anatomically modern humans (AMHs) differ from the W-shaped pattern found in most anthropoid primates. AMHs are characterized by a drastically lowered high-frequency cutoff and maintaining high sensitivity in the low to midfrequencies, resulting in a U-shaped audiogram (1-7). In primates, such hearing variability is assumed to be partly related to forms of vocalization and habitat acoustics (8-10). Diverse hearing capabilities are also related to the morphology of the diminutive middle ear ossicles housed in the tympanic cavity (11, 12). The malleus, incus, and stapes form the ossicular chain that connects the tympanic membrane to the oval window of the inner ear. These bones play an important role in audition by amplifying and regulating the sound waves transmitted to the cochlea (11,(13)(14)(15). In particular, the middle ear acts as a transformer that matches the impedances between the air and the pe...

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Section: Discussionmentioning

confidence: 99%

Morphology and function of Neandertal and modern human ear ossicles

Stoessel

David

Gunz

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Semilandmarks were slid to the GPA average to minimize bending energy between each specimen and the GPAconsensus. Missing data were few and estimated using the thin-plates spline approach available to 3D semilandmark techniques (Gunz et al, 2009;Bastir et al, 2011;Bastir et al, 2013c). Size was measured as centroid size and shape as Procrustes shape coordinates (O'Higgins, 2000).…”

Section: Geometric Morphometric Analysesmentioning

confidence: 99%

The relevance of the first ribs of the El Sidrón site (Asturias, Spain) for the understanding of the Neandertal thorax

Bastir

García‐Martínez

Estalrrich

et al. 2015

Journal of Human Evolution

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The paleobiological significance of the rib cage in Neanderthal ranges from functional anatomy, energetics to the general evolution of human body shape. However, despite this importance there is still debate as to the nature and extent of variations in size and shape of the Neanderthal thorax.The El Sidrón Neanderthals can contribute to this debate providing new thoracic remains (N=245) ranging from fully preserved and undistorted ribs to highly fragmented elements.

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“…By contrast, modern humans developed a more globular shape of the brain primarily resulting from a bulging in the parietal areas and a ventral flexion ( figure 3). In addition, modern humans display a proportionally larger cerebellum, larger olfactory bulbs and temporal lobe poles, and a wider orbitofrontal cortex [118]. As the skull develops and evolves as a tightly integrated structure [119], it is currently not well understood to what extent endocranial shape differences primarily result from variation in brain structure, or correlate with species differences in facial and mandibular size and shape.…”

Section: Large-brained Late Pleistocene Homininsmentioning

confidence: 99%

Brain ontogeny and life history in Pleistocene hominins

Hublin

Neubauer

Gunz

2015

Phil. Trans. R. Soc. B

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A high level of encephalization is critical to the human adaptive niche and emerged among hominins over the course of the past 2 Myr. Evolving larger brains required important adaptive adjustments, in particular regarding energy allocation and life history. These adaptations included a relatively small brain at birth and a protracted growth of highly dependent offspring within a complex social environment. In turn, the extended period of growth and delayed maturation of the brain structures of humans contribute to their cognitive complexity. The current palaeoanthropological evidence shows that, regarding life history and brain ontogeny, the Pleistocene hominin taxa display different patterns and that one cannot simply contrast an 'ape-model' to a 'human-model'. Large-brained hominins such as Upper Pleistocene Neandertals have evolved along their own evolutionary pathway and can be distinguished from modern humans in terms of growth pattern and brain development. The life-history pattern and brain ontogeny of extant humans emerged only recently in the course of human evolution.

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Evolution of the base of the brain in highly encephalized human species

Cited by 155 publications

References 54 publications

Morphology and function of Neandertal and modern human ear ossicles

Morphology and function of Neandertal and modern human ear ossicles

The relevance of the first ribs of the El Sidrón site (Asturias, Spain) for the understanding of the Neandertal thorax

Brain ontogeny and life history in Pleistocene hominins

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