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Early hominin auditory capacities.

Quam R, Martínez I, Rosa M, Bonmatí A, Lorenzo C, de Ruiter DJ, Moggi-Cecchi J, Conde Valverde M, Jarabo P, Menter CG, Thackeray JF, Arsuaga JL - Sci Adv (2015)

Bottom Line: Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures.Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies.The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats.

View Article: PubMed Central - PubMed

Affiliation: Department of Anthropology, Binghamton University [State University of New York (SUNY)], Binghamton, NY 13902-6000, USA. ; Centro de Investigación (UCM-ISCIII) sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos, 5, 28029 Madrid, Spain. ; Division of Anthropology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA.

ABSTRACT
Studies of sensory capacities in past life forms have offered new insights into their adaptations and lifeways. Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures. We have studied the anatomy of the outer and middle ear in the early hominin taxa Australopithecus africanus and Paranthropus robustus and estimated their auditory capacities. Compared with chimpanzees, the early hominin taxa are derived toward modern humans in their slightly shorter and wider external auditory canal, smaller tympanic membrane, and lower malleus/incus lever ratio, but they remain primitive in the small size of their stapes footplate. Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies. The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats.

No MeSH data available.


Related in: MedlinePlus

Measurements of the middle and outer ear (A to C) and ear ossicles (D).(A), (B), (C1), (C2), and (D) are not drawn to the same scale. (A) to (C) are based on the 3D reconstruction of the left side of HTB 1769 (Pan troglodytes), showing the EAC (gray), the middle ear cavity (green), the aditus ad antrum (red), the mastoid antrum and connected mastoid air cells (blue), the inner ear (orange), and the temporal bone (yellow). P1, limit between the mastoid antrum and the connected mastoid air cells with the aditus ad antrum. P2, entrance to the aditus ad antrum from the middle ear cavity. P3, medial edge of the tympanic groove (sulcus tympanicus). P4, cross section perpendicular to the long axis of the EAC that meets the lateral end of the tympanic groove. (A) VMA, volume of the mastoid antrum and connected mastoid air cells, measured dorsal to P1; VMEC, volume of the middle ear cavity, bounded by P2 to P3. (B) LAD, length of the aditus ad antrum, measured as the distance from the center of P1 to the center of P2; AAD1, area of the exit of the aditus ad antrum to the mastoid antrum and connected mastoid air cells; AAD2, area of the entrance to the aditus ad antrum from the middle ear cavity. For modeling purposes, we have calculated the radius (RAD1 and RAD2; not shown), which would correspond to a circle with the given area for the exit (AAD1) and entrance (AAD2). (C1) LEAC, length of the EAC, measured from the most lateral extent of the tympanic groove (defined by P4) to the spina suprameatum. In Pan, the spina suprameatum is replaced by the superior-most point of the porus acusticus externus. (C2) RTM1, half of the measured greater diameter of the tympanic membrane, measured in P3; RTM2, half of the measured lesser diameter (perpendicular to RTM1) of the tympanic membrane, measured in P3; REAC1 and REAC2, half of the measured diameters of the two major perpendicular axes (superoinferior and mediolateral) of the EAC measured at P4. (D) is based on the profiles of the malleus and incus from the temporal bone AT-1907 and the stapes from Cranium 5. LM, functional length of the malleus, measured as the maximum length from the superior border of the lateral process to the inferior-most tip of the manubrium; LI, functional length of the incus, measured from the lateral-most point along the articular facet to the lowest point along the long crus in the rotational axis; AFP, measured area of the footplate of the stapes.
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Figure 1: Measurements of the middle and outer ear (A to C) and ear ossicles (D).(A), (B), (C1), (C2), and (D) are not drawn to the same scale. (A) to (C) are based on the 3D reconstruction of the left side of HTB 1769 (Pan troglodytes), showing the EAC (gray), the middle ear cavity (green), the aditus ad antrum (red), the mastoid antrum and connected mastoid air cells (blue), the inner ear (orange), and the temporal bone (yellow). P1, limit between the mastoid antrum and the connected mastoid air cells with the aditus ad antrum. P2, entrance to the aditus ad antrum from the middle ear cavity. P3, medial edge of the tympanic groove (sulcus tympanicus). P4, cross section perpendicular to the long axis of the EAC that meets the lateral end of the tympanic groove. (A) VMA, volume of the mastoid antrum and connected mastoid air cells, measured dorsal to P1; VMEC, volume of the middle ear cavity, bounded by P2 to P3. (B) LAD, length of the aditus ad antrum, measured as the distance from the center of P1 to the center of P2; AAD1, area of the exit of the aditus ad antrum to the mastoid antrum and connected mastoid air cells; AAD2, area of the entrance to the aditus ad antrum from the middle ear cavity. For modeling purposes, we have calculated the radius (RAD1 and RAD2; not shown), which would correspond to a circle with the given area for the exit (AAD1) and entrance (AAD2). (C1) LEAC, length of the EAC, measured from the most lateral extent of the tympanic groove (defined by P4) to the spina suprameatum. In Pan, the spina suprameatum is replaced by the superior-most point of the porus acusticus externus. (C2) RTM1, half of the measured greater diameter of the tympanic membrane, measured in P3; RTM2, half of the measured lesser diameter (perpendicular to RTM1) of the tympanic membrane, measured in P3; REAC1 and REAC2, half of the measured diameters of the two major perpendicular axes (superoinferior and mediolateral) of the EAC measured at P4. (D) is based on the profiles of the malleus and incus from the temporal bone AT-1907 and the stapes from Cranium 5. LM, functional length of the malleus, measured as the maximum length from the superior border of the lateral process to the inferior-most tip of the manubrium; LI, functional length of the incus, measured from the lateral-most point along the articular facet to the lowest point along the long crus in the rotational axis; AFP, measured area of the footplate of the stapes.

Mentions: To address this question more directly, we have studied the skeletal structures of the outer and middle ear and modeled the auditory capacities in several early hominin individuals, chimpanzees, and modern humans (see Materials and Methods and the Supplementary Materials). To measure the anatomical variables of the outer and middle ear (Fig. 1), we relied mainly on virtual [three-dimensional (3D) computed tomography (CT)] reconstructions, complemented by direct measurements on other specimens where these anatomical regions are exposed (see Materials and Methods and the Supplementary Materials; fig. S1). Subsequently, we modeled the pattern of sound power transmission through the outer and middle ear up to 5.0 kHz in several of the most complete early hominin individuals, as well as in chimpanzees and modern humans (see Materials and Methods and the Supplementary Materials; figs. S2 to S12 and tables S1 to S3). The model includes a number of skeletal variables (Fig. 1) that can be measured in fossil specimens and considers the function of each of the components of the outer and middle ear, their acoustic and mechanical properties, and the way in which they interact (30). The soft tissue variables that cannot be measured in fossil specimens were held constant in the model for all taxa.


Early hominin auditory capacities.

Quam R, Martínez I, Rosa M, Bonmatí A, Lorenzo C, de Ruiter DJ, Moggi-Cecchi J, Conde Valverde M, Jarabo P, Menter CG, Thackeray JF, Arsuaga JL - Sci Adv (2015)

Measurements of the middle and outer ear (A to C) and ear ossicles (D).(A), (B), (C1), (C2), and (D) are not drawn to the same scale. (A) to (C) are based on the 3D reconstruction of the left side of HTB 1769 (Pan troglodytes), showing the EAC (gray), the middle ear cavity (green), the aditus ad antrum (red), the mastoid antrum and connected mastoid air cells (blue), the inner ear (orange), and the temporal bone (yellow). P1, limit between the mastoid antrum and the connected mastoid air cells with the aditus ad antrum. P2, entrance to the aditus ad antrum from the middle ear cavity. P3, medial edge of the tympanic groove (sulcus tympanicus). P4, cross section perpendicular to the long axis of the EAC that meets the lateral end of the tympanic groove. (A) VMA, volume of the mastoid antrum and connected mastoid air cells, measured dorsal to P1; VMEC, volume of the middle ear cavity, bounded by P2 to P3. (B) LAD, length of the aditus ad antrum, measured as the distance from the center of P1 to the center of P2; AAD1, area of the exit of the aditus ad antrum to the mastoid antrum and connected mastoid air cells; AAD2, area of the entrance to the aditus ad antrum from the middle ear cavity. For modeling purposes, we have calculated the radius (RAD1 and RAD2; not shown), which would correspond to a circle with the given area for the exit (AAD1) and entrance (AAD2). (C1) LEAC, length of the EAC, measured from the most lateral extent of the tympanic groove (defined by P4) to the spina suprameatum. In Pan, the spina suprameatum is replaced by the superior-most point of the porus acusticus externus. (C2) RTM1, half of the measured greater diameter of the tympanic membrane, measured in P3; RTM2, half of the measured lesser diameter (perpendicular to RTM1) of the tympanic membrane, measured in P3; REAC1 and REAC2, half of the measured diameters of the two major perpendicular axes (superoinferior and mediolateral) of the EAC measured at P4. (D) is based on the profiles of the malleus and incus from the temporal bone AT-1907 and the stapes from Cranium 5. LM, functional length of the malleus, measured as the maximum length from the superior border of the lateral process to the inferior-most tip of the manubrium; LI, functional length of the incus, measured from the lateral-most point along the articular facet to the lowest point along the long crus in the rotational axis; AFP, measured area of the footplate of the stapes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 1: Measurements of the middle and outer ear (A to C) and ear ossicles (D).(A), (B), (C1), (C2), and (D) are not drawn to the same scale. (A) to (C) are based on the 3D reconstruction of the left side of HTB 1769 (Pan troglodytes), showing the EAC (gray), the middle ear cavity (green), the aditus ad antrum (red), the mastoid antrum and connected mastoid air cells (blue), the inner ear (orange), and the temporal bone (yellow). P1, limit between the mastoid antrum and the connected mastoid air cells with the aditus ad antrum. P2, entrance to the aditus ad antrum from the middle ear cavity. P3, medial edge of the tympanic groove (sulcus tympanicus). P4, cross section perpendicular to the long axis of the EAC that meets the lateral end of the tympanic groove. (A) VMA, volume of the mastoid antrum and connected mastoid air cells, measured dorsal to P1; VMEC, volume of the middle ear cavity, bounded by P2 to P3. (B) LAD, length of the aditus ad antrum, measured as the distance from the center of P1 to the center of P2; AAD1, area of the exit of the aditus ad antrum to the mastoid antrum and connected mastoid air cells; AAD2, area of the entrance to the aditus ad antrum from the middle ear cavity. For modeling purposes, we have calculated the radius (RAD1 and RAD2; not shown), which would correspond to a circle with the given area for the exit (AAD1) and entrance (AAD2). (C1) LEAC, length of the EAC, measured from the most lateral extent of the tympanic groove (defined by P4) to the spina suprameatum. In Pan, the spina suprameatum is replaced by the superior-most point of the porus acusticus externus. (C2) RTM1, half of the measured greater diameter of the tympanic membrane, measured in P3; RTM2, half of the measured lesser diameter (perpendicular to RTM1) of the tympanic membrane, measured in P3; REAC1 and REAC2, half of the measured diameters of the two major perpendicular axes (superoinferior and mediolateral) of the EAC measured at P4. (D) is based on the profiles of the malleus and incus from the temporal bone AT-1907 and the stapes from Cranium 5. LM, functional length of the malleus, measured as the maximum length from the superior border of the lateral process to the inferior-most tip of the manubrium; LI, functional length of the incus, measured from the lateral-most point along the articular facet to the lowest point along the long crus in the rotational axis; AFP, measured area of the footplate of the stapes.
Mentions: To address this question more directly, we have studied the skeletal structures of the outer and middle ear and modeled the auditory capacities in several early hominin individuals, chimpanzees, and modern humans (see Materials and Methods and the Supplementary Materials). To measure the anatomical variables of the outer and middle ear (Fig. 1), we relied mainly on virtual [three-dimensional (3D) computed tomography (CT)] reconstructions, complemented by direct measurements on other specimens where these anatomical regions are exposed (see Materials and Methods and the Supplementary Materials; fig. S1). Subsequently, we modeled the pattern of sound power transmission through the outer and middle ear up to 5.0 kHz in several of the most complete early hominin individuals, as well as in chimpanzees and modern humans (see Materials and Methods and the Supplementary Materials; figs. S2 to S12 and tables S1 to S3). The model includes a number of skeletal variables (Fig. 1) that can be measured in fossil specimens and considers the function of each of the components of the outer and middle ear, their acoustic and mechanical properties, and the way in which they interact (30). The soft tissue variables that cannot be measured in fossil specimens were held constant in the model for all taxa.

Bottom Line: Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures.Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies.The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats.

View Article: PubMed Central - PubMed

Affiliation: Department of Anthropology, Binghamton University [State University of New York (SUNY)], Binghamton, NY 13902-6000, USA. ; Centro de Investigación (UCM-ISCIII) sobre Evolución y Comportamiento Humanos, Avda. Monforte de Lemos, 5, 28029 Madrid, Spain. ; Division of Anthropology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA.

ABSTRACT
Studies of sensory capacities in past life forms have offered new insights into their adaptations and lifeways. Audition is particularly amenable to study in fossils because it is strongly related to physical properties that can be approached through their skeletal structures. We have studied the anatomy of the outer and middle ear in the early hominin taxa Australopithecus africanus and Paranthropus robustus and estimated their auditory capacities. Compared with chimpanzees, the early hominin taxa are derived toward modern humans in their slightly shorter and wider external auditory canal, smaller tympanic membrane, and lower malleus/incus lever ratio, but they remain primitive in the small size of their stapes footplate. Compared with chimpanzees, both early hominin taxa show a heightened sensitivity to frequencies between 1.5 and 3.5 kHz and an occupied band of maximum sensitivity that is shifted toward slightly higher frequencies. The results have implications for sensory ecology and communication, and suggest that the early hominin auditory pattern may have facilitated an increased emphasis on short-range vocal communication in open habitats.

No MeSH data available.


Related in: MedlinePlus