Evolution of the auditory ossicles in extant hominids: metric variation in <scp>A</scp>frican apes and humans

Quam, Rolf; Coleman, Mark N.; Martínez, Inmaculada Penadés

doi:10.1111/joa.12197

Cited by 19 publications

(55 citation statements)

References 64 publications

(210 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent analyses have emphasized a distinctly derived morphology of the ossicles of AMHs compared with extant great apes (17,18), suggesting that the ossicles of extinct hominins may provide insights into the origin of the distinct auditory capacities of AMHs.…”

mentioning

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.

View full text Add to dashboard Cite

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...

show abstract

mentioning

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.

View full text Add to dashboard Cite

show abstract

“…Flohr et al () addressed this concern about positioning in their “Procedure 1” (one observer checking two images of each incus positioned twice, revealing a near‐statistically significant difference, P = 0.071). We doubt that not having sex information affected our findings, as there are no gender differences in auditory ossicles (Quam et al, ), nor a significant gender difference in adults' aerated mastoid size (Cinamon, ).…”

Section: Discussionmentioning

confidence: 80%

“…Reports of angles of incus axes in both the physical anthropology (Flohr et al, ; Quam et al, 2013; Quam et al, ; Quam and Rak, ) and medical literature (Kamrava et al, ) are few. Quam et al () discuss the malleus‐incus lever ratio (generally about 1.2–1.3 for humans) and assume the manubrium is oriented directly perpendicular to the rotational axis. Dobrev et al (), as have others, show that over the acoustic frequency spectrum useable by modern humans, that the physiologic axis of malleus‐incus rotation (hinged rotational motion) coincides with the anatomic axis of rotation for frequencies below 1.5 kHz.…”

Section: Discussionmentioning

confidence: 99%

“…). The definition of axes of incus was as written by both Flohr et al () and Quam et al (): x ‐axis (long process axis): “Defined by a line joining the tip of the long process to the most salient point along the superior border of the body.” y ‐axis (short process axis): “Defined by a line joining the tip of the short process to the most salient point along the anterior portion of the superior border of the body.” …”

Section: Methodsmentioning

confidence: 99%

“…The digital image is of a right ear's incus as viewed from the lateral aspect. The y ‐axis is from “the tip of the short process to the most salient point along the anterior portion of the superior border of the body.” The x ‐axis is from “the tip of the long process to the most salient point along the superior border of the body” (as written by Quam et al, and Flohr et al, ). The background 1 mm grid verifies that magnification is uniformly rectilinear.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Angles of Axes of Incudes

Specht

Todd

2019

The Anatomical Record

View full text Add to dashboard Cite

Incus angles of axes (the angle between "short process axis" and the "long process axis") are more open in humans than chimpanzees: 64.0 versus 55.7 degrees (Quam et al.: J Anat 225 (2014) 167-196). However, Flohr et al. (Anat Rec 293 (2010) 2094-2106) raise concern about interobserver agreement of the axes. The concern is important as phylogenetic relationships of mammals are inferred from the incus (and malleus and stapes). We sought to check (1) interobserver agreement; and (2) if the angles of the axes of incudes (incuses) exhibit bilateral symmetry, which is expected if the axes are genetically determined. We studied incudes from 41 modern adult crania with clinically normal temporal bones. Angles of axes were determined on rectilinear digital photographs of incudes in standard lateral orientation. Two observers independently drew the axes and measured the axes. Interobserver agreement was within 4 degrees for 24 of 34 left-sided incudes and for 27 of 35 right-sided incudes. The mean of the two observers' angle determinations were used. Left incudes' median was 67 degrees, range 60-73; right 67.5 degrees, range 58-77. Bilateral symmetry of angles of axes was found: r = 0.55, N = 31, 95% CI 0.24-0.75. Angles of axes of modern human incudes are probably genetically determined features, but are of doubtful physiologic or evolutionary advantage in modern humans. Interobserver agreement of angles of modern human axes is concerning and must be specified in reports. Consideration should be given to a convention to designate axes in ambiguous cases. Anat Rec, 302:1615-

show abstract

Morphometry of auditory ossicles in medieval human remains from Central Europe

Krenz‐Niedbała

Łukasik

Macudziński

et al. 2021

The Anatomical Record

View full text Add to dashboard Cite

Human auditory ossicles, the malleus, the incus, and the stapes, are located in the tympanic cavity in the temporal bone and through forming a chain for the sound transmission from the tympanic membrane to the cochlea, they play an important role in the hearing process. Despite their clinical, phylogenetic, and evolutionary significance, the morphometry of the human ear bones has not been examined systematically. The ear ossicles are the smallest bones of the human skeleton, attaining their final size and morphology already at birth. Initially, they have been found to exhibit minimal morphometric variation, but further studies brought the opposite results. The aim of this study was to examine the morphometric variation of human auditory ossicles recovered from medieval and postmedieval subadult skeletons from Poland, Central Europe.The analysis involved in a total of 166 ear bones. Their measurements were performed on microscopic images using CorelDraw x4, according to a protocol of Quam and Rak with modification of Flohr et al. and Wadhwa et al. Our study showed a significant metric variation in the measurements taken at areas of the greatest morphological variability of the ossicles. We found that greater linear dimensions were associated with lower values of angular measurements. These results reveal the inherent variation found in these supposed functionally constrained structures. Representation of even greater number of populations, time periods, and developmental stages are needed. Further study will expand our understanding of the global scope of variation found in ear ossicular morphology and its functional implications for paleoanthropology.

show abstract

Evolution of the auditory ossicles in extant hominids: metric variation in African apes and humans

Cited by 19 publications

References 64 publications

Morphology and function of Neandertal and modern human ear ossicles

Morphology and function of Neandertal and modern human ear ossicles

Angles of Axes of Incudes

Morphometry of auditory ossicles in medieval human remains from Central Europe

Contact Info

Product

Resources

About