The ear ossicles and the evolution of the primate ear: A biomechanical approach

From a morphometric viewpoint the variability of human and other primate ear ossicles appears to be suitable for the study of taxonomic and phylogenetic distinction among Primates. It may also be of interest to determine whether they are useful to show differences in the perception of sound from the environment and from conspecifics. The energy transmitted through the ossicles is mantained by the action of different leverages. These modify the action of the ossicles from relatively wide, low energy, movements of the hammer to the smaller, high energy, movements of the stirrup. It seems that the pongid type of ossicle leverage combination saves more energy, possibly with a certain loss of subtle information, but this may be more useful in the wild than decoding voice modulation. The human type leverage, being less demultiplied, may produce a major loss of energy but, perhaps, a more precise conservation of sound information useful for speech communication.     

Morphometrics of human auditory ossicles from Antinoe Necropolis (Egypt)

Historical evidence suggests that the Christian Coptic population of Antinoe necropolis, probable descendants of Dynastic Egyptians, may reflect admixture from Greek and Roman populations. Within the anthropological surveys on Antinoe skeletal remains (A.D. 300–600), a sample of auditory ossicles was compared with a Dynastic Egyptian sample (“G. Marro” osteological collection), from Asiut and Gebelen Univariate and multivariate statistical analyses were applied, to this end. The auditory ossicles are generally larger in the Coptic group; in both groups shape measurements have a high variability, while size measurements are relatively invariable. Univariate variances are homogeneous but the means are significantly different. This suggests genetic changes, but identical patterns of variation. The stepwise discriminant functions analysis and the Generalized Distance, suggesting a biological heterogeneity in the Antinoe sample in spite of some similarity of the two groups, tend to support this. Further analyses of the auditory ossicles in Greek and Roman populations are however needed to confirm the gene flow hypothesis in the Antinoe population, suggested by historical data.     

The origin of modern humans: A cytogenetic model

A new model of the origin of man is proposed on the basis of recent studies on cytogenetics of chromosomal Q-heterochromatin regions (Q-HRs) in man and other higher primates. This model is based on the following facts: a) chromosomal Q-HRs were found in the genome of only three higher primates (man, the chimpanzee and the gorilla); b) chromosomal Q-HRs in the human genome, unlike those in apes, exhibit considerable quantitative variability; c) the number of human chromosomal Q-HRs in the genome has a selective value in the adaptation of human populations to various environmental conditions. According to this model, the three major morphofunctional distinctions of man—great physiological flexibility, characteristic morphological structure, and conceptual thinking—arose as a result of the capacity of our remote ancestors to broadly change their genome mass owing to features of chromosomal Q-HRs that are only intrinsic to man. We feel that genome-mass variability through chromosomal Q-HRs allowed man to adapt himself to various environments over such a short period of time.     

Two-year-old children copy more reliably and more often than nonhuman great apes in multiple observational learning tasks

Individuals observing a proficient model can potentially benefit by copying at least one of the following three elements: motor movements (i.e., actions), goals, and results. Although several studies have investigated this issue in human infants, there are still very few studies that have systematically examined great apes’ ability to spontaneously copy each of these three elements (particularly in comparison with human infants). We tested great apes and human children with eight two-target puzzle boxes—with varying levels of difficulty—to isolate the aspects that the various species may be more prone to copying. We found first trial evidence for observational learning of actions, goals, and results in children. Some copying was found for apes as well, but only if their performance was averaged across trials.     

Age-independent constancy of mineral contents in human vertebra and auditory ossicle

To elucidate age-related changes of mineral contents in human bones, element contents of human vertebrae and auditory ossicles were determined by inductively coupled plasma atomic-emission spectrometry. The cervical, thoracic, and lumbar vertebrae were removed from 12 vertebral columns. The mallei of auditory ossicle were removed from 27 cadavers. It was found that average relative contents (RCs) of calcium and phosphorus in cervical, thoracic, and lumbar vertebrae remained almost constant within ages ranging from 46 to 99 y. In addition, it was found that the RCs of calcium and phosphorus in men’s and women’s mallei remained constant within ages ranging from 40 to 98 yr. These results support the view that there is no significant agedependent change of mineral contents in human bones.     

Potentialities of temporal bone computed tomography in the identification of causes of hypoacusis of postinflammatory genesis

Temporal bone computed tomography (CT) was used to examine 64 patients with impaired hearing due to inflammatory diseases of the middle year. In 21 patients, the pathological process was bilateral. A total of 85 series of temporal bone CT scans were analyzed. The patients' age ranged from 2 to 66 years. CT verified adhesive otitis media in 62 cases, otosclerosis in 7, local malformation of the auditory ossicles and/or the labyrinthine fenestrae in 11. No CT changes were revealed in 5 cases. The CT symptoms of adhesive otitis media were identified. These included soft tissue bands and/or soft tissue-density portions that fix the auditory ossicles or block the niches of the labyrinthine fenestrae (31 temporal bones); sclerosis or ossification of the ligaments and tendons of the middle ear (7 temporal bones); calcification foci in the tympanic cavity (9 cases); osteosclerotic changes in the epitympanus (2 cases); cicatricial changes in the tympanic membrane (24 cases); destructive changes in the auditory ossicles (19 temporal bones). There has been evidence that CT may be used for the differential diagnosis of adhesive otitis media from otosclerosis and congenital malformations of the structures of the middle ear.     

Fluorescent heterochromatin staining in primate chromosomes

Recently, in addition to quinacrine staining, fluorochrome techniques have been developed which brilliantly stain other heterochromatic regions. Two of these staining techniques are Distamycin/DAPI (DA/DAPI) and D287/170. We stained the chromosomes of all species of great apes and 14 species of primates (48 individuals) using these three fluorochrome techniques. Only african apes and man show brilliant quinacrine staining while, man and all the great apes show brilliant DA/DAPI staining and only species belonging to the hominoidea (including the siamang) showed bright D287/170 staining. In the lower primates a medium level of DA/DAPI fluorescence was found in some species with large amount of pericentromeric heterochromatin. Brilliant DA/DAPI staining could represent a derived trait linking all great apes and humans, while D287/170 may link all hominoidea. Fluorochrome staining is believed to be correlated with some satellite DNA sequences. However, data available on the chromosome location of satellite DNAs in non-human primates were derived from buoyant density fractions resulting in cross hybridization and now are not considered reliable. Before making any correlation between fluorochrome staining and satellite DNAs in non human primates there is need of data onin situ hybridization with cloned DNA sequences on primate chromosomes. These data would help clarify the evolution and relationship of satellite DNAs and heterochromatin in primates.     

Development of the Laryngeal Air Sac in Chimpanzees

Though many nonhuman primates possess a laryngeal sac, the great apes are unique in their great size. Though an enlarged sac probably arose in their common ancestor, its functional adaptations remain a matter of debate. Its development in extant great apes is likely to provide valuable information to clarify the issue. We used magnetic resonance imaging to examine the development of the laryngeal sac in 3 living chimpanzees, age 4 mo–5 yr, and identified 2 distinct growth phases of the sac. A gradual growth of the sac in early infancy results in a configuration so that it occupies the ventral region of the neck; many adult nonhominoid primates having a sac show the configuration. The subsequent rapid expansion of the sac in late infancy causes the final configuration in chimpanzees, wherein the sac expands into the pectoral, clavicular, and axillary regions. The latter phase possibly arose at latest in the last common ancestor of extant great apes and contributed to the evolution of the enlarged sac, despite the later evolutionary diversification in adult sac anatomy and growth. As many studies have advocated, the enlarged sac probably plays a role in vocalization in adults. However, physiological modifications in the laryngeal region during infancy are likely to provide valuable information to evaluate the functional adaptations of the enlarged sac in the great apes.     

Skeletal studies of the people of Sicily: An update on research into human remains from archaeological contexts

Human skeletal remains, commonly at the focus of the archaeological investigations of cemeteries, recently have become of increasing importance in reconstructing the culture history of Sicily. A review of the history of osteological investigations on Sicily, including note of recent studies, demonstrates the considerable progress made in recent years and provides future researchers with indications of directions that are available to be taken. This list provides an update to an earlier study (Becker 1995–96). We now have a more useful indication of the extent of human skeletal material now available from Sicilian archaeological sites, from all periods, that may be used in comparative studies.     

Correlations between auditory structures and hearing sensitivity in non‐human primates

Primates show distinctions in hearing sensitivity and auditory morphology that generally follow phylogenetic patterns. However, few previous studies have attempted to investigate how differences in primate hearing are directly related to differences in ear morphology. This research helps fill this void by exploring the form‐to‐function relationships of the auditory system in a phylogenetically broad sample of non‐human primates. Numerous structures from the outer, middle, and inner ears were measured in taxa with known hearing capabilities. The structures investigated include the overall size and shape of the pinna, the areas of the tympanic membrane and stapedial footplate, the masses and lever arm lengths of the ossicles, the volumes of the middle ear cavities, and the length of the cochlea. The results demonstrate that a variety of auditory structures show significant correlations with certain aspects of hearing (particularly low‐frequency sensitivity). Although the majority of these relationships agree with expectations from auditory theory, some traditional (and possibly outdated) ideas were not supported. For example, the common misconception that higher middle ear transformer ratios (e.g., impedance transformer ratio) result in increased hearing sensitivity was not supported. Although simple correlations between form and function do not necessarily imply causality, the relationships defined in this study not only increase our understanding of auditory patterns in extant taxa but also lay the foundation to begin investigating the hearing in fossil primates. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Origin of the human hand

A means of determining the phylogenetic implications of similarities between the hands of man and non-human primates is proposed. The only traits shared by man and non-human primates accepted as evidence of our ancestral hand structure and functions are those which are incompatible or out of keeping with current behavior of the human hand. They may be assumed to remain only as relics of adaptations to former habits of locomotion and feeding. The relics found through this analysis are all traits that are present in the apes (some of them only in African apes) and probably related to functions of the hand in suspension of the body, fist-walking, and knuckle-walking. The presence of these traits in man implies that human ancestors similarly used the hand to suspend the body in the trees and to support it on the back of the flexed fingers.     

Higher rate of evolution of X chromosome alpha-repeat DNA in human than in the great apes.

The rate of introduction of neutral mutations is lower in man than in other primates, including the chimpanzee. This species is generally regarded as our closest relative among the great apes. We present here an analysis of sequences of X chromosomal alphoid repetitive DNA from man and the great apes, which supports the closer relationship between man and chimpanzee and indicates a considerably increased rate of recombination in the human repeat DNA. These results indicate that the 'molecular clock' is running more quickly in man.     

Comparative anatomy and histology of xenarthran osteoderms

Reconstruction of soft tissues in fossil vertebrates is an enduring challenge for paleontologists. Because inferences must be based on evidence from hard tissues (typically bones or teeth), even the most complete fossils provide only limited information about certain organ systems. Osteoderms ("dermal armor") are integumentary bones with high fossilization potential that hold information about the anatomy of the skin in many extant and fossil amniotes. Their importance for functional morphology and phylogenetic research has recently been recognized, but studies have focused largely upon reptiles, in which osteoderms are most common. Among mammals, osteoderms occur only in members of the clade Xenarthra, which includes armadillos and their extinct relatives: glyptodonts, pampatheres, and, more distantly, ground sloths. Here, I present new information on the comparative morphology and histology of osteoderms and their associated soft tissues in 11 extant and fossil xenarthrans. Extinct mylodontid sloths possessed simple, isolated ossicles, the presence of which is likely plesiomorphic for Xenarthra. More highly derived osteoderms of glyptodonts, pampatheres, and armadillos feature complex articulations and surface ornamentation. Osteoderms of modern armadillos are physically associated with a variety of soft tissues, including nerve, muscle, gland, and connective tissue. In some cases, similar osteological features may be caused by two or more different tissue types, rendering soft-tissue inferences for fossil osteoderms equivocal. Certain osteological structures, however, are consistently associated with specific soft-tissue complexes and therefore represent a relatively robust foundation upon which to base soft-tissue reconstructions of extinct xenarthrans.     

In search of the last common ancestor: new findings on wild chimpanzees

Modelling the behaviour of extinct hominins is essential in order to devise useful hypotheses of our species'' evolutionary origins for testing in the palaeontological and archaeological records. One approach is to model the last common ancestor (LCA) of living apes and humans, based on current ethological and ecological knowledge of our closest living relations. Such referential modelling is based on rigorous, ongoing field studies of the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus). This paper reviews recent findings from nature, focusing on those with direct implications for hominin evolution, e.g. apes, using elementary technology to access basic resources such as food and water, or sheltering in caves or bathing as thermoregulatory adaptations. I give preference to studies that directly address key issues, such as whether stone artefacts are detectible before the Oldowan, based on the percussive technology of hammer and anvil use by living apes. Detailed comparative studies of chimpanzees living in varied habitats, from rainforest to savannah, reveal that some behavioural patterns are universal (e.g. shelter construction), while others show marked (e.g. extractive foraging) or nuanced (e.g. courtship) cross-populational variation. These findings allow us to distinguish between retained, primitive traits of the LCA versus derived ones in the human lineage.     

An evolutionary conserved early replicating segment on the sex chromosomes of man and the great apes

Replication studies on prometaphase chromosomes of man, the chimpanzee, the pygmy chimpanzee, the gorilla, and the orangutan reveal great interspecific homologies between the autosomes. The early replicating X chromosomes clearly show a high degree of conservation of both the pattern and the time course of replication. An early replicating segment on the short arm of the X chromosomes of man (Xp22.3) which escapes inactivation can be found on the X chromosomes of the great apes as well. Furthermore, the most early replicating segment on the Y chromosomes of all species tested appears to be homologous to this segment on the X chromosomes. Therefore, these early replicating segments in the great apes may correspond to the pseudoautosomal segment proposed to exist in man. From further cytogenetic characterization of the Y chromosomes it is evident that structural alterations have resulted in an extreme divergence in both the euchromatic and heterochromatic parts. It is assumed, therefore, that, in contrast to the X chromosomes, the Y chromosomes have undergone a rapid evolution within the higher primates.     

A case of spontaneous acquisition of a human sound by an orangutan

The capacity of nonhuman primates to actively modify the acoustic structure of existing sounds or vocalizations in their repertoire appears limited. Several studies have reported population or community differences in the acoustical structure of nonhuman primate long distance calls and have suggested vocal learning as a mechanism for explaining such variation. In addition, recent studies on great apes have indicated that there are repertoire differences between populations. Some populations have sounds in their repertoire that others have not. These differences have also been suggested to be the result of vocal learning. On yet another level great apes can, after extensive human training, also learn some species atypical vocalizations. Here we show a new aspect of great ape vocal learning by providing data that an orangutan has spontaneously (without any training) acquired a human whistle and can modulate the duration and number of whistles to copy a human model. This might indicate that the learning capacities of great apes in the auditory domain might be more flexible than hitherto assumed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Licking of the Neonate and Duration of Labor in Great Apes and Man

An hypothesis recently advanced by Montagu relates the cutaneous stimulation of prolonged labor in great apes and man to the proper functioning of the newborn. These exceptional primates, according to Montagu, do not therefore stimulate the newborn by licking, as is the case for mammals in which labor is of short duration. Though man is believed to differ from other primates, especially the apes, in duration and difficulty of labor, we present data to show that the case at present rests on unstandardized measures of durations and on incomplete anatomical arguments. Until more objective criteria for charting the progress of labor are developed, there is no way of knowing if the assumption of a significant difference is correct. In any case, there seems to be no valid basis for linking differences in labor among primates with different forms of postpartum care, of which licking is but one example.     

Effects of different kinds of cranial deformation on the incidence of wormian bones

Researchers have debated whether the presence and frequency of wormian bones (sutural bones, supernumerary bones, and ossicles) are attributable to genetic factors, environmental factors, or both. This research examines the effects of many different kinds of cranial deformation on the incidence of wormian bones. A sample of 127 deformed and undeformed crania from New World archaeological sites was examined. An undeformed cranial sample (n=35) was compared to the following cranially deformed groups: 1) occipital, 2) lambdoid, 3) annular, 4) fronto-vertico-occipital, 5) parallelo-fronto-occipital, and 6) sagittal synostosis. Three levels of degree of cultural cranial deformation were qualitatively determined. Type and number of wormian bones along each major suture were recorded for each cranium. Group means were analyzed using Kruskal-Wallis one-way ANOVA statistical tests to test the null hypothesis that cranial deformation does not have an effect on wormian bone incidence. Results indicate that all forms of cranial deformation affect the frequency of some types of wormian bones. In particular, all cranially deformed groups exhibited significantly greater frequencies of lambdoid ossicles. Apical, parieto-mastoid, and occipito-mastoid wormian bones also appeared with greater frequency in some groups of culturally deformed crania. Further, varying degrees of cultural deformation all had more lambdoid wormian bones than the undeformed group. These results suggest that wormian bone development in posteriorly placed sutures may be affected more by environmental forces than are their anteriorly placed counterparts.     

Morphometric affinities of the human shoulder

To analyze differences between apes and monkeys and the affinities of man, we have studied the shoulder girdle of 327 specimens of anthropoid primates. The scapula, clavicle and humerus are viewed as an integrated functional complex on the basis of 18 measurements. Several varieties of multivariate analysis show that man is clearly closer to other hominoids than to the included monkey taxa (whether terrestrial or arboreal, Old World or New World). The marked shoulder differences between apes and monkeys and similarities between apes and man correlate with the muscular anatomy, which in hominoids allows the motions involved in their locomotion and feeding behavior. As the hominid-pongid correspondence in shoulder morphology is especially detailed regarding the functionally important joint surfaces, it is consistent with a fairly recent period of common ancestry and behavior. No hypothetical evolutionary pathway or ancestral form of the human shoulder need look far beyond the model afforded by extant pongids. In contrast with previous studies on the primate shoulder, these results agree with information accumulating from other systems—comparative anatomy, primate behavior, and molecular biology — in suggesting very close relationship between man and extant African pongids.     

Plantigrady and foot adaptation in African apes: implications for hominid origins.

In living primates, except the great apes and humans, the foot is placed in a heel-elevated or semi-plantigrade position when these animals move upon arboreal or terrestrial substrates. Heel placement and bone positions in the non-great ape primate foot are designed to increase mobility and flexibility in the arboreal environment. Orangutans have further enhanced foot mobility by adapting their feet for suspension and thus similarly utilize foot positions where the heel does not touch the substrate. Chimpanzees and gorillas represent an alternative pattern (plantigrady), in which the heel contacts the surface of the support at the end of swing phase, especially during terrestrial locomotion. Thus, chimpanzees and gorillas possess feet adapted for both arboreal and terrestrial substrates. African apes also share several osteological features related to plantigrady and terrestrial locomotion with early hominids. From this analysis, it is apparent that hominid locomotor evolution passed through a quadrupedal terrestrial phase.