The descended larynx is not uniquely human

Morphological modifications of vocal anatomy are widespread among vertebrates, and the investigation of the physiological mechanisms and adaptive functions of such variants is an important focus of research into the evolution of communication. The "descended larynx" of adult humans has traditionally been considered unique to our species, representing an adaptation for articulate speech, and debate concerning the position of the larynx in extinct hominids assumes that a lowered larynx is diagnostic of speech and language. Here, we use bioacoustic analyses of vocalizing animals, together with anatomical analyses of functional morphology, to document descended larynges in red and fallow deer. The resting position of the larynx in males of these species is similar to that in humans, and, during roaring, red-deer stags lower the larynx even further, to the sternum. These findings indicate that laryngeal descent is not uniquely human and has evolved at least twice in independent lineages. We suggest that laryngeal descent serves to elongate the vocal tract, allowing callers to exaggerate their perceived body size by decreasing vocal-tract resonant frequencies. Vocal-tract elongation is common in birds and is probably present in additional mammals. Size exaggeration provides a non-linguistic alternative hypothesis for the descent of the larynx in human evolution.     

The third metacarpal styloid process in humans: origin and functions

The development, mechanics, and pathology of the third carpometacarpal joint have been investigated in order to explain the unique presence in humans of a styloid process on the third metacarpal. Structure and functions of the joint are compared in a large series of Old World anthropoid hand skeletons, cadavers, and X-rays, and shown to differ in the three groups. Developmental anomalies reveal the source of the human styloid in a group of cells which fuse with the capitate in other Old World Anthropoidea. The absence of the process in Australopithecus afarensis and its presence in Neandertals suggest that an explanation for the evolution of the process may be sought in stresses on the hand in stone tool-use. Film analysis of stone tool-use shows that hammering and digging with hand-held stones direct forces on the palmar aspect of the metacarpal head. From a biomechanical analysis of these forces it may be seen that the styloid process prevents subluxation of the base. The effectiveness of the process in this function is reflected by the rarity of injury and arthritis in the region. Individuals lacking the process tend to undergo degeneration of bone at the joint. Since repetitive impulsive forces on joints are known to cause osteoarthritis, it is suggested that there may be a link between the increasing reliance of early hominids on manipulative behavior that stressed this region of the hand and the evolution of a structural pattern that protects the joint from these stresses.     

The attachments of the lateral and medial ends of the extensor retinaculum of the human wrist

The attachments of the lateral and medial ends of the extensor retinaculum of the human wrist were observed in 52 human upper limbs (from 26 cadavers) by dissection. In all the specimens used in this study, the lateral end of the retinaculum was found to be attached to the distal part of the anterior border of the radius and its medial end was attached to the styloid process of the ulna, the pisiform and the triquetrum.     

Palatal plane inclination on vertical growth pattern among Indians

The skeletal discrepancies in the vertical dimensions can either lead to a long face or a short face. The palatal plane inclination is one such contributing factor. The study sample comprised of 15 lateral cephalograms collected between the time period of June 2019 - March 2020 with 5 cephalograms belonging to skeletal Class I, II and III respectively. The inclination angle and mandibular plane angle were measured using the FACAD software. The obtained results were tabulated and statistically analysed using Pearson''s correlation test to determine the correlation between the two variables. There was a statistically significant negative correlation between the skeletal malocclusions with a p value of 0.011. Thus, palatal plane inclination is not a major contributing factor for vertical growth pattern and it is suggestive of a multifactorial influence.     

Comparative morphology of the hyo-laryngeal complex in anthropoids: two steps in the evolution of the descent of the larynx

The descent of the larynx is a key phenomenon not only in postnatal development, but also in the evolution of human speech. The positional change of the larynx is affected by the descent of the hyoid bone in relation to the mandible and cranial base, and that of the laryngeal framework in relation to the hyoid bone. The phylogeny of the spatial configuration of the hyo-laryngeal complex is one of the most important sources of information for elucidating the evolution of laryngeal descent. In the present study, the anatomy of the complex was examined in various species of anthropoids to compare the configuration, the shape of the basihyal and thyroid cartilage, and the length of the lateral thyrohyoid ligaments. Non-human hominoids share most features with humans, while cercopithecoids and ceboids have anatomical features that sharply contrast to humans, except for the form of the thyroid cartilage in ceboids. The laryngeal framework in hominoids is well separated from and assured of mobility independent of the hyoid. In cercopithecoids and ceboids, it is, by contrast, locked into and tied tightly with the hyoid so that the hyo-laryngeal complex acts as a functional unit. This spatial configuration is considered to be significantly related to the mechanism that prevents aspiration, including epiglottic movement and vestibular closure. Non-human hominoids are inferred to share the mechanism with human adults, not with cercopithecoids and ceboids, although their larynx is located as high as the latter. Consequently, it is hypothesized that the descent of the larynx evolved in two steps. The first step would have been descent of the thyroid in relation to the hyoid for the evolution of the mechanism preventing aspiration, which occurred in the common ancestor of hominoids. The second step, descent of the hyoid within the neck, occurred during hominid evolution for human speech. Electronic Publication     

Advances in understanding the relationship between the skull base and larynx with comments on the origins of speech

The position of upper respiratory structures, such as the larynx, has proven to be of great importance in determining an animal’s breathing, swallowing and vocalizing abilities. Studies on living mammals have also shown that the shape of the basicranium is related to the position of the larynx. This information has been of value in using the skull base as a means to reconstruct the upper respiratory tract of fossil hominids. Ongoing comparative and experimental studies of this region are adding new information on the mechanical relationship of the skull base to contiguous areas of the respiratory tract. For example, examination of the region in mammals disparate from humans, such as cetaceans, and experimental work on the region in rats, is adding new data on how the larynx and skull base may functionally interact.     

Measurements of postnatal growth of the skull of Pan troglodytes verus using lateral cephalograms

The postnatal growth of the viscerocranium in relation to the neurocranium of Pan troglodytes verus has been investigated using standardized lateral cephalograms. Sex and age were determined on the basis of cranial morphology and the skulls were divided into four age groups: infantile, juvenile, subadult and adult. The cephalograms were traced on transparencies and specific anatomical landmarks were identified for the measurement of lines angles and the area of the neurocranium and viscerocranium. The results showed that the skull of Pan troglodytes verus exhibits klinorhynchy. During postnatal growth it develops towards airorhynchy, but never shows true airorhynchy. In the infantile age group the measured area of the neurocranium is larger than that of the viscerocranium. The measured area of the viscerocranium increases until adulthood and is larger than that of the neurocranium in the subadult and adult group. From the results we conclude that in Pan troglodytes verus growth of the neurocranium seizes early in juvenile individuals, whereas the viscerocranium grows until adulthood. This may reflect an adaptation to the masticatory system.     

Descent of the hyoid in chimpanzees: evolution of face flattening and speech

The human supralaryngeal vocal tract develops to form a unique two-tube configuration with equally long horizontal and vertical cavities. This anatomy contributes greatly to the morphological foundations of human speech. It is believed to depend on the reduced growth of the palate and on the developmental descent of the larynx relative to the palate. Anatomically, the descent of the larynx is accomplished through both the descent of the laryngeal skeleton relative to the hyoid and the descent of the hyoid relative to the palate. We have studied the development of three living chimpanzees using magnetic resonance imaging. Our previous study showed that, as in humans, chimpanzees show rapid laryngeal descent, with changes in the relative proportion of the vocal tract during early infancy. However, this is not accompanied by the descent of the hyoid relative to the palate, although it is achieved with the descent of the laryngeal skeleton relative to the hyoid. Here, we show that subsequently the chimpanzee hyoid also descends to maintain the rapid descent of the larynx, similarly to humans. We argue that the descent of the larynx probably evolved in a common ancestor of extant hominoids, originally to confer an advantage via a function unrelated to speech. Thus, the descent of the larynx per se is not unique to humans, and facial flattening was probably the major factor that paved the way for speech in the human lineage.     

Increased breathing control: Another factor in the evolution of human language

Investigation into the evolution of human language has involved evidence of many different kinds and approaches from many different disciplines. For full modern language, humans must have evolved a range of physical abilities for the production of our complex speech sounds, as well as sophisticated cognitive abilities. Human speech involves free‐flowing, intricately varied, rapid sound sequences suitable for the fast transfer of complex, highly flexible communication. Some aspects of human speech, such as our ability to manipulate the vocal tract to produce a wide range of different types of sounds that form vowels and consonants, have attracted considerable attention from those interested in the evolution of language. 1 , 2 However, one very important contributory skill, the human ability to attain very fine control of breathing during speech, has been neglected. Here we present evidence of the importance of breathing control to human speech, as well as evidence that our capabilities greatly exceed those of nonhuman primates. Human speech breathing demands fine neurological control of the respiratory muscles, integrated with cognitive processes and other factors. Evidence from comparison of the vertebral canals of fossil hominids and those of extant primates suggests that a major increase in thoracic innervation evolved in later hominid evolution, providing enhanced breathing control. If that is so, then earlier hominids would have had quite restricted speech patterns, whereas more recent hominids, with human‐like breath control abilities, would have been capable of faster, more varied speech sequences.     

Approche paléontologique de l’évolution du langage : un état des lieux

One of the most influential paleoanthropological approaches to the question of language origins has been the attempt to reconstruct the supralaryngeal vocal tract (SVT) in fossil humans. In particular, the low placement of the larynx was considered to be a uniquely human feature and was interpreted as a specific adaptation to produce human speech. Nevertheless, based on the anatomy of the basicranium and the hyoid bone, various researchers reached different conclusions regarding the placement of the larynx in human fossils, especially in Neandertals. Further, the recent finding of a low placement of the larynx in chimpanzees, calls into question the basic premise on which much of this research has been based. To overcome this, we have proposed and developed a new line of research into the question of speech capabilities in fossil specimens which is focused not on the ability to produce the sounds of spoken language, but on the capacity to perceive them. The modern human auditory pattern is unique among primates in showing a relatively heightened sensitivity to the midrange frequencies between 2-4 kHz, a frequency range which coincides with that of spoken language. Our analysis shows that the preserved skeletal anatomy of the outer and middle ear in the Middle Pleistocene hominids from the site of the Sima de los Huesos is compatible with human-like auditory capacities, and is clearly different from chimpanzees in the midrange frequencies. These results strongly suggest that the anatomical structures which support the modern hum and pattern of intraspecific communication were already present in these human ancestors. Further, the presence of a common condition in both the modern human and Neandertal evolutionary lineages suggests this represents an ancient adaptation within the genus Homo.     

Hand and foot remains from the Gran Dolina Early Pleistocene site (Sierra de Atapuerca, Spain).

We report here the study of the 22 hand and foot remains from the Early Pleistocene level TD6 of the Gran Dolina site at Sierra de Atapuerca (Burgos, Spain) recovered from 1994 to 1996. These remains are paratypes of Homo antecessor. All of the elements are briefly described and compared with other fossil hominids. The capitate has a constricted neck, well developed head, strong attachment for the ligamentum interosseum trapezoid-capitate, a palmarly placed trapezoid facet with a distinctive small dorsal trapezoid facet, a highly curved and oblique orientation of the second metacarpal facet, and a transversally oriented dorsodistal border. A hamate with a moderately projecting and lightly built hamulus; an inferred reduced styloid process on the third metacarpal base; a wide second metacarpal head; and middle phalanges with well marked insertions for the flexor digitorum superficialis muscle and wide heads. The morphology and dimensions of the pedal remains from TD6 are very similar to modern humans; but the base, proximal articular surface and shafts of the proximal hallucal phalanges are more rounded and the midshaft of the proximal toe phalanx is wider.     

Longitudinal study of dental development in chimpanzees of known chronological age: Implications for understanding the age at death of Plio-Pleistocene hominids

Reconstruction of life history variables of fossil hominids on the basis of dental development requires understanding of and comparison with the pattern and timing of dental development among both living humans and pongids. Whether dental development among living apes or humans provides a better model for comparison with that of Plio-Pleistocene hominids of the genus Australopithecus remains a contentious point. This paper presents new data on chimpanzees documenting developmental differences in the dentitions of modern humans and apes and discusses their significance in light of recent controversies over the human or pongid nature of australopithecine dental development. Longitudinal analysis of 299 lateral head radiographs from 33 lab-reared chimpanzees (Pan troglodytes) of known chronological age allows estimation of means and standard deviations for the age at first appearance of 8 developmental stages in the mandibular molar dentition. Results are compared with published studies of dental development among apes and with published standards for humans. Chimpanzees are distinctly different from humans in two important aspects of dental development. Relative to humans, chimpanzees show advanced molar development vis a vis anterior tooth development, and chimpanzees are characterized by temporal overlap in the calcification of adjacent molar crowns, while humans show moderate to long temporal gaps between the calcification of adjacent molar crowns. In combination with recent work on enamel incremental markers and CAT scans of developing dentitions of Plio-Pleistocene hominids, this evidence supports an interpretation of a rapid, essentially “apelike” ontogeny among australopithecines. © 1996 Wiley-Liss, Inc.     

Axial and appendicular skeleton of Homo antecessor.

The human trunk and limb bones recovered from the Gran Dolina site, in the Sierra de Atapuerca (Burgos, Spain) are studied. All these fossils were excavated at the level called TD6 between 1994 and 1995 and have been dated in excess of 780,000 years ago. These remains have been recently attributed to a new Homo species named Homo antecessor. Axial (vertebrae and ribs) and part of the appendicular (clavicles, radii, femur and patellae) skeleton are studied here. Hand and foot bones have been studied elsewhere (Lorenzo et al., 1999). Four is the minimum number of individuals represented by the postcranial remains recovered up to now. All elements are briefly described anatomically, measured and compared with other fossil hominids and modern humans in order to establish, as far as possible, what postcranial morphology characterized this new species of our genus.The H. antecessor postcrania, generally, display a set of morphological traits that are more similar to modern humans than to the Middle and Upper Pleistocene European hominids. Our results do not contradict the previous phylogenetic analysis, i.e., that H. antecessor represents the last common ancestor for H. sapiens (modern humans) and H. neanderthalensis (Neandertals).     

Soft tissue facial profile of normal dental and skeletal subjects in Croatian population aged 12 to 15 years

This study was carried out on 40 lateral cephalograms of Croatian subjects aged 12 to 15 years with dental and skeletal class I. The purpose of this investigation was to determine the means and standard deviations of the soft tissue parameters in the sample of Croatian population exhibiting dental and skeletal class I and to find the correlations between investigated parameters. The investigation included a total of 11 variables of which 4 were angular and 7 linear. Linear and angular measurements were made to the nearest 0.5 mm or 0.5 degree with dial calipers and a standard protractor with 0.5 degree increments. Data from this investigation could serve to determine the norms of 11 soft tissue variables for Croatian population with dental and skeletal class I, and to define craniofacial morphology of the soft tissue profile in patients with normal occlusion. Significant correlations were found between thickness of upper and lower lip, and between the distance of upper and lower lip to the Ricketts esthetic line, and Holdaway angle.     

The basicranium of Plio-Pleistocene hominids as an indicator of their upper respiratory systems

Our analyses of extant primates have shown that a relationship exists between the degree of flexion of the basicranium and the location of upper respiratory structures such as the larynx and pharynx (Laitman et al., 1978). Based upon these relationships, we have previously used the basicrania of late Pleistocene hominids as a guide to the reconstruction of their upper respiratory anatomy (Laitman et al., 1979). This study continues our approach by examining the basicrania of Plio-Pleistocene hominids and reconstructing their upper respiratory systems. Nine Plio-Pleistocene hominids had basicrania complete enough to be used in this study. These included the originals of Sts 5, MLD 37/38, SK 47, SK 48, SK 83, Taung, KNM-ER 406, OH 24, and a cast of OH 5. Craniometric analysis of the basicrania of these specimens showed that they had marked similarities to those of extant pongids. These basicranial similarities between Plio-Pleistocene hominids and extant apes suggest that the upper respiratory systems of these groups were also alike in appearance. As with living nonhuman primates, the early hominids probably exhibited a larynx and pharynx positioned high in the neck. This high position would have permitted an intranarial epiglottis to be present during both normal respiration and the ingestion of a liquid bolus of food. The high position of the larynx would have also greatly restricted the supralaryngeal portion of the pharynx available to modify laryngeal sounds. It is thus possible that the Plio-Pleistocene hominids exhibited modes of breathing, swallowing and vocalizing similar to those of living apes.     

Dental size variation in the Atapuerca-SH Middle Pleistocene hominids

The Middle Pleistocene Atapuerca-Sima de los Huesos (SH) site in Spain has yielded the largest sample of fossil hominids so far found from a single site and belonging to the same biological population. The SH dental sample includes a total of 452 permanent and deciduous teeth, representing a minimum of 27 individuals. We present a study of the dental size variation in these hominids, based on the analysis of the mandibular permanent dentition: lateral incisors, n=29; canines, n=27; third premolars, n=30; fourth premolars, n=34; first molars, n=38; second molars, n=38. We have obtained the buccolingual diameter and the crown area (measured on occlusal photographs) of these teeth, and used the bootstrap method to assess the amount of variation in the SH sample compared with the variation of a modern human sample from the Museu Antropologico of the Universidade of Coimbra (Portugal). The SH hominids have, in general terms, a dental size variation higher than that of the modern human sample. The analysis is especially conclusive for the canines. Furthermore, we have estimated the degree of sexual dimorphism of the SH sample by obtaining male and female dental subsamples by means of sexing the large sample of SH mandibular specimens. We obtained the index of sexual dimorphism (ISD=male mean/female mean) and the values were compared with those obtained from the sexed modern human sample from Coimbra, and with data found in the literature concerning several recent human populations. In all tooth classes the ISD of the SH hominids was higher than that of modern humans, but the differences were generally modest, except for the canines, thus suggesting that canine size sexual dimorphism in Homo heidelbergensis was probably greater than that of modern humans. Since the approach of sexing fossil specimens has some obvious limitations, these results should be assessed with caution. Additional data from SH and other European Middle Pleistocene sites would be necessary to test this hypothesis.     

Trigeminal foraminal pattern in the face

The integration of the trigeminal nerve into the craniofacial skeleton was studied by examining cephalometrically the relationships of the openings of the branches of the trigeminal nerve to each other and to other structures. Lateral cephalograms were taken from 30 adult skulls; several linear and angular dimensions were measured from the cephalograms. The results suggest a relationship between nerve growth and bone growth in the craniofacial skeleton.     

The anatomy, physiology, acoustics and perception of speech: essential elements in analysis of the evolution of human speech

Inferences on the evolution of human speech based on anatomical data must take into account its physiology, acoustics and perception. Human speech is generated by the supralaryngeal vocal tract (SVT) acting as an acoustic filter on noise sources generated by turbulent airflow and quasi-periodic phonation generated by the activity of the larynx. The formant frequencies, which are major determinants of phonetic quality, are the frequencies at which relative energy maxima will pass through the SVT filter. Neither the articulatory gestures of the tongue nor their acoustic consequences can be fractionated into oral and pharyngeal cavity components. Moreover, the acoustic cues that specify individual consonants and vowels are “encoded”, i.e., melded together. Formant frequency encoding makes human speech a vehicle for rapid vocal communication. Non-human primates lack the anatomy that enables modern humans to produce sounds that enhance this process, as well as the neural mechanisms necessary for the voluntary control of speech articulation. The specific claims of Duchin (1990) are discussed.     

Neandertal capitate-metacarpal articular morphology

Neandertal capitate-metacarpal 2 and 3 articulations have been observed to differ in orientation and shape from those of more recent humans. To evaluate this, we tested for differences in capitate-metacarpal 2 (MC2) and MC2-capitate facet orientations and MC2 and MC3 robusticity indices, and for multivariate shape equivalence of the capitate-MC2/MC3 facets and the MC3 diaphysis and styloid process between samples of Neandertals and recent humans. Canonical discriminant functions of log size-and-shape and log shape transformed measurements were run on variables of the capitate-MC2 and MC3 facets, and these plus MC3 diaphysis and styloid process variables. The null hypothesis of shape equivalence is rejected for both variable sets. Modern human capitate-MC morphology results from nonallometric increases in distal capitate breadth and the projection of the MC3 styloid process, and reductions in MC2 facet height and MC3 facet breadth. These shape changes are associated with a significantly less parasagittal orientation of the capitate-MC2 facets in recent humans, but are only trivially correlated with MC 2 and 3 robusticity indices. The recent human capitate-MC 2 and 3 morphology may reflect a shift in habitual joint reaction forces from more axial to more oblique forces while maintaining similar pronation/supination of the MC2. However, the full behavioral implications of these contrasts remain unclear. Am J Phys Anthropol 103:219–233, 1997. © 1997 Wiley-Liss, Inc.