Twinning frequency in catarrhine primates

It has been repeatedly suggested that twinning frequency in most catarrhine primates is approximately the same as in humans, whereas the frequency in the chimpanzee and the gorilla might be higher. This study presents a re-evaluation of the evidence from the pertinent literature. It can be demonstrated that most data on twinning frequency in Old World monkeys and apes should not be used because of their small sample size. A lower limit of 1500 pregnancies is suggested here. If all frequency estimates taken from smaller samples are rejected, only four estimates forMacaca mulatta andPapio hamadryas remain. The estimates range from 0.19 to 0.35% and are in fact lower than the frequencies of most (but necessarily all) human populations. The published birth samples for apes are, however, relatively small, and the resulting twinning rates may not be reliable.     

Relative growth of the limbs and trunk in the African apes

Examination of relative growth and allometry is important for our understanding of the African apes, as they represent a closely related group of species of increasing body size. This study presents a comparison of ontogenetic relative growth patterns of some postcranial dimensions in Pan paniscus, Pantroglodytes, and Gorilla gorilla. Interspecific proportion differences among the three species are also analyzed. It is stressed that reliable ontogenetic information can only be obtained if subadults are examined-growth data cannot be inferred from static adult scaling. Results indicate that some postcranial relative growth patterns are very similar in the three species, suggesting differential extrapolation of a common growth pattern, whereas for other proportion comparisons the growth trends differ markedly among the species, producing distinct shape differences in the adults Interspecific shape changes among the three species are characterized by positive allometry of chest girth and negative allometry of body height and leg length. It is suggested that relative decrease of leg length with increasing body size among the African pongids might be expected on biomechanical grounds, in order to maintain similar locomotor abilities of climbing arborealism and quadrupedal terrestrialism. Relative to body weight or trunk length, the limbs of the bonobo (Pan paniscus) are longer than in the common chimpanzee or the gorilla, with a lower intermembral index. This may most closely resemble the primitive condition for the African apes.     

Are social media reports useful for assessing small ape occurrence? A pilot study from Peninsular Malaysia

Citizen science-based research has been used effectively to estimate animal abundance and breeding patterns, to monitor animal movement, and for biodiversity conservation and education. Here, we evaluate the feasibility of using social media observations to assess the distribution of small apes in Peninsular Malaysia. We searched for reports of small ape observations in Peninsular Malaysia on social media (e.g., blogs, Facebook, Instagram, Twitter, YouTube, iNaturalist, etc.), and also used online, radio, print messaging, and word of mouth to invite citizen scientists such as birders, amateur naturalists, hikers, and other members of the public to provide information about small ape observations made during their activities. These reports provided new information about the occurrence of all three species of small apes (Hylobates agilis, Hylobates lar, and Symphalangus syndactylus) in Peninsular Malaysia. Social media users reported observations of small apes in almost every state. Despite the fact that small apes are believed to occur primarily in the interior of large forested areas, most observations were from fairly small (<100 km²) forests near areas of high traffic and high human population (roads and urban areas). This suggests that most outdoor enthusiasts primarily visit well-traveled and easily accessible areas, which results in biased sampling if only incidental observations reported on social media are used. A more targeted approach specifically soliciting reports from citizen scientists visiting large, less-accessible forests may result in better sampling in these habitats. Social media reports indicated the presence of small apes in at least six habitats where they had not been previously reported. We verified the reported data based on whether reports included a date, location, and uploaded photographs, videos and/or audio recordings. Well-publicized citizen science programs may also build awareness and enthusiasm about the conservation of vulnerable wildlife species.     

Observed frequency of monozygotic twinning in Holstein dairy cattle

Bonnier's equation is used to mathematically estimate the frequency of monozygotic (MZ) twinning in epidemiologic studies of twinning in dairy cattle; however, no empirical determination of MZ twinning has been reported in the literature. Our objectives were to empirically determine the frequency of MZ twinning in lactating Holstein cows and to compare this result with published estimates predicted using Bonnier's equation. Ear biopsies were collected from 107 sets of Holstein twins from six Wisconsin dairies resulting in 40 opposite-sex twins, 29 same-sex male twins, and 38 same-sex female twins. To empirically determine the frequency of MZ twinning, DNA extracted from ear biopsies collected from the 67 same-sex twins was PCR amplified using primers for a minimum of 5 polymorphic microsatellite DNA markers. Opposite-sex twins were classified as dizygotic (DZ) as well as same-sex twins differing in at least one microsatellite DNA marker. Same-sex twins were classified as MZ when all genotypes for a minimum of five markers were identical. Of the 67 same-sex twins, 62 were classified as DZ and 5 MZ resulting in a MZ twinning frequency of 7.5% of same-sex twins and 4.7% of all twins. The estimated frequency of MZ twinning in this population of twin calves using Bonnier's equation was 39.5% of same-sex twins and 24.7% of all twins. We concluded that MZ twinning occurred infrequently in Holstein cattle and perhaps less frequently than that reported in studies using Bonnier's equation to estimate MZ twinning.     

Morphometric analysis of hominoid lower molars from Yuanmou of Yunnan Province, China

Shape analyses of cross-sectional mandibular molar morphology, using Euclidean Distance Matrix Analysis, were performed on 79 late Miocene hominoid lower molars from Yuanmou of Yunnan Province, China. These molars were compared to samples of chimpanzee, gorilla, orangutan,Lufengpithecus lufengensis, Sivapithecus, Australopithecus afarensis, and human mandibular molars. Our results indicate that the cross-sectional shape of Yuanmou hominoid lower molars is more similar to the great apes that to humans. There are few differences between the Yuanmou,L. lufengensis, andSivapithecus molars in cross-sectional morphology, demonstrating strong affinities between these three late Miocene hominoids. All three of the fossil samples show strong similarities to orangutans. From this, we conclude that these late Miocene hominoids are more closely related to orangutants than to either the African great apes or humans.     

Phyletic size change and brain/body allometry: A consideration based on the African pongids and other primates

A problematic aspect of brain/body allometry is the frequency of interspecific series which exhibit allometry coefficients of approximately 0.33. This coefficient is significantly lower than the 0.66 value which is usually taken to be the interspecific norm. A number of explanations have been forwarded to account for this finding. These include (1) intraspecificallometry explanations, (2) nonallometric explanations, and (3) Jerison’s “extraneurons” hypothesis, among others. The African apes, which exhibit a lowered interspecific allometry coefficient, are used here to consider previous explanations. These are found to be inadequate in a number of ways, and an alternative explanation is proposed. This explanation is based on patterns of brain and body size change during ontogeny and phytogeny. It is argued that the interspecific allometry coefficient in African apes parallels the intraspecific one because similar ontogenetic modifications of body growth separate large and small forms along each curve. In both cases, body size differences are produced primarily by growth in later postnatal periods, during which little brain growth occurs. Data on body growth, neonatal scaling, and various lifehistory traits support this explanation. This work extends previous warnings that sizecorrected estimates of relative brain size may not correspond very closely to our understanding of the behavioral capacities of certain species in lineages characterized by rapid change in body size.     

When can noninvasive samples provide sufficient information in conservation genetics studies?

Noninvasive sampling, of faeces and hair for example, has enabled many genetic studies of wildlife populations. However, two prevailing problems common to these studies are small sample sizes and high genotyping errors. The first problem stems from the difficulty in collecting noninvasive samples, particularly from populations of rare or elusive species, and the second is caused by the low quantity and quality of DNA extracted from a noninvasive sample. A common question is therefore whether noninvasive sampling provides sufficient information for the analyses commonly conducted in conservation genetics studies. Here, we conducted a simulation study to investigate the effect of small sample sizes and genotyping errors on the precision and accuracy of the most commonly estimated genetic parameters. Our results indicate that small sample sizes cause little bias in measures of expected heterozygosity, pairwise F_ST and population structure, but a large downward bias in estimates of allelic diversity. Allelic dropouts and false alleles had a much smaller effect than missing data, which effectively reduces sample size further. Overall, reasonable estimates of genetic variation and population subdivision are obtainable from noninvasive samples as long as error rates are kept below a frequency of 0.2. Similarly, unbiased estimates of population clustering can be made with genotyping error rates below 0.5 when the populations are highly differentiated. These results provide a useful guide for researchers faced with studying the conservation genetics of small, endangered populations from noninvasive samples.     

Body weight prediction in early fossil hominids: Towards a taxon-“independent” approach

The choice of a model taxon is crucial when investigating fossil hominids that clearly do not resemble any extant species (such as Australopithecus) or show significant differences from modern human proportions (such as Homo habilis OH 62). An “interhominoid” combination is not adequate either, as scaling with body weight is strongly divergent in African apes and humans for most skeletal predictors investigated here. Therefore, in relation to a study of seven long bone dimensions, a new taxon-“independent” approach is suggested. For a given predictor, its taxonomic “independence” is restricted to the size range over which the body weight-predictor relationship for African apes and humans converges. Different predictors produce converging body weight estimates (BWEs) for different size ranges: taxon-“independent” estimates can be calculated for small- and medium-sized hominids (e. g., for weights below 50 kg) using femoral and tibial dimensions, whereas upper limb bones provide converging results for large hominids (above 50 kg). If the remains of Australopithecus afarensis really belong to one species, the relationship of male (above 60 kg) to female body weight (approximately 30 kg) does not fall within the observed range of modern hominoids. Considering Sts 14 (22 kg) to represent a small-sized Australopithecus africanus, the level of encephalization lies well above that of extant apes. If OH 62 (approximately 25 kg), with limb proportions less human-like than those of australopithecines, indeed represents Homo habilis (which has been questioned previously), an increase in relative brain size would have occurred well before full bipedality, an assumption running counter to current assumptions concerning early human evolution. © 1993 Wiley-Liss, Inc.     

Enamel hypoplasia in the deciduous teeth of great apes: variation in prevalence and timing of defects

The prevalence of enamel hypoplasia in the deciduous teeth of great apes has the potential to reveal episodes of physiological stress in early stages of ontogenetic development. However, little is known about enamel defects of deciduous teeth in great apes. Unresolved questions addressed in this study are: Do hypoplastic enamel defects occur with equal frequency in different groups of great apes? Are enamel hypoplasias more prevalent in the deciduous teeth of male or female apes? During what phase of dental development do enamel defects tend to form? And, what part of the dental crown is most commonly affected? To answer these questions, infant and juvenile skulls of two sympatric genera of great apes (Gorilla and Pan) were examined for dental enamel hypoplasias. Specimens from the Powell‐Cotton Museum (Quex Park, UK; n = 107) are reported here, and compared with prior findings based on my examination of juvenile apes at the Cleveland Museum of Natural History (Hamman‐Todd Collection; n = 100) and Smithsonian Institution (National Museum of Natural History; n = 36). All deciduous teeth were examined by the author with a ×10 hand lens, in oblique incandescent light. Defects were classified using Fédération Dentaire International (FDI)/Defects of Dental Enamel (DDE) standards; defect size and location on the tooth crown were measured and marked on dental outline charts. Enamel defects of ape deciduous teeth are most common on the labial surface of canine teeth. While deciduous incisor and molar teeth consistently exhibit similar defects with prevalences of ～10%, canines average between 70–75%. Position of enamel defects on the canine crown was analyzed by dividing it into three zones (apical, middle, and cervical) and calculating defect prevalence by zone. Among gorillas, enamel hypoplasia prevalence increases progressively from the apical zone (low) to the middle zone to the cervical zone (highest), in both maxillary and mandibular canine teeth. Results from all three study collections reveal that among the great apes, gorillas (87–92%) and orangutans (91%) have a significantly higher prevalence of canine enamel defects than chimpanzees (22–48%). Sex differences in canine enamel hypoplasia are small and not statistically significant in any great ape. Factors influencing intergroup variation in prevalence of enamel defects and their distribution on the canine crown, including physiological stress and interspecific dento‐gnathic morphological variation, are evaluated. Am J Phys Anthropol 116:199–208, 2001. © 2001 Wiley‐Liss, Inc.     

Positional behavior in the Hominoidea

Quantitative studies on the positional behavior of members of the Hominoidea are compared in order (1) to identify consistencies across the superfamily, (2) to contrast ape positional behavior with that of Old World monkeys (forest-livingPapio anubis were chosen for study to reduce body size effects), and (3) to identify distinctive behaviors in each of the ape taxa. Differences in the way behaviors were sampled in the various studies necessitated considering posture and locomotion separately. Unimanual arm-hanging and vertical climbing were the most distinctive shared postural and locomotor modes among the apes (the gorilla excepted), constituting ≥5.0% and ≥4.9% of all behavior in each species. Arm-hanging and brachiation (sensu stricto) frequencies were the highest by far in hylobatids. Hand-foot hanging, bipedal posture, and clambering, an orthograde suspensory locomotion assisted by the hindlimbs, were more common in orangutans than in any other hominoid. Sitting and walking were observed in the highest frequencies in the African apes but were no more common than in the baboon. Relatively high frequencies of brachiation (sensu stricto) were reported for all apes except chimpanzees and gorillas. Brachiation and arm-hanging were kinematically different in apes and baboons, involving complete humeral abduction only in the former, whereas vertical climbing appeared to be kinematically similar in apes and baboons. It is concluded that the morphological specializations of the apes may be adaptations to (1) the unique physical demands of arm-hanging and (2) less kinematically distinct, but still quantitatively significant, frequencies of vertical climbing.     

A correction for allele frequency estimates derived from isofemale lines

Isofemale lines are commonly used inDrosophila and other genera for the purpose of assaying genetic variation. Isofemale lines can be kept in the laboratory for many generations before genetic work is carried out, and permit the confirmation of newly discovered alleles. A problem not realized by many workers is that the commonly used estimate of allele frequency from these lines is biased. This estimation bias occurs at all times after the first laboratory generation, regardless of whether single individuals or pooled samples are used in each well of an electrophoretic gel. This bias can potentially affect the estimation of population genetic parameters, and in the case of rare allele analysis it can cause gross overestimates of gene flow. This paper provides a correction for allele frequency estimates derived from isofemale lines for any time after the lines are established in the laboratory. When pooled samples are used, this estimator performs better than the standard estimator at all times after the first generation. The estimator is also insensitive to multiple inseminations. After the lines have drifted oneN _e generations, multiple inseminations actually make the new estimator perform better than it does in singly inseminated females. Simulations show that estimates made using either estimator after the lines have drifted to fixation have a much greater error associated with their use than do those estimates made earlier in time using the correction. In general it is better to use corrected estimates of gene frequency soon after lines are established than to use uncorrected estimates made after the first laboratory generation. This work was supported by an NSERC fellowship to A.D.L.     

Spatial and temporal genetic differentiation and effective population size of brown trout (<Emphasis Type="Italic">Salmo trutta</Emphasis>, L.) in small Danish rivers

The spatial and temporal genetic structure of brown trout populations from three small tributaries of Lake Hald, Denmark, was studied using analysis of variation at eight microsatellite loci. From two of the populations temporal samples were available, separated by up to 13 years (3.7 generations). Significant genetic differentiation was observed among all samples, however, hierarchical analysis of molecular variance (AMOVA) showed that differentiation among populations accounted for a non-significant amount of the genetic differentiation, whereas differentiation among temporal samples within populations was highly significant (0.0244, P<0.001). Estimates of effective population size (N _e) using a maximum-likelihood based implementation of the temporal method, yielded small values (N _e ranging from 33 to 79). When a model was applied that allows for migration among populations, N _e estimates were even lower (24–54), and migration rates were suggested to be high (0.13–0.36). All samples displayed a clear signal of a recent bottleneck, probably stemming from a period of unfavourable conditions due to organic pollution in the 1970–1980’s. By comparison to other estimates of N _e in brown trout, Lake Hald trout represent a system of small populations linked by extensive gene flow, whereas other populations in larger rivers exhibit much higher N _e values and experience lower levels of immigration. We suggest that management considerations for systems like Lake Hald brown trout should focus both on a regional scale and at the level of individual populations, as the future persistence of populations depends both on maintaining individual populations and ensuring sufficient migration links among these populations.     

AN ELECTROPHORETIC INVESTIGATION OF INTRAGAMETOPHYTIC SELFING IN EQUISETUM ARVENSE

Because homosporous pteridophytes (Psilotophyta, Arthrophyta, most Microphyllophyta and Pteridophyta) produce bisexual gametophytes, it was maintained that high levels of inbreeding would characterize these plants. Electrophoretic evidence was used to estimate the frequency of intragametophytic selfing in Equisetum arvense (Arthrophyta). A total of 669 samples from 17 populations was examined from western North America. Although some populations exhibited as many as seven or eight genotypes, 10 populations were each characterized by only a single genotype; eight of these populations were heterozygous for one or more loci. For most populations, estimates of intragametophytic self-fertilization are 0.000, indicating that virtually all matings involve different gametophytes. Genetic data corroborate predictions based on earlier field and laboratory investigations of Equisetum gametophytes. These detailed studies demonstrated that in many species, including E. arvense, gametophytes are initially either male or female; only later and in the absence of fertilization do some gametophytes become bisexual. Our findings join a growing electrophoretic data base which demonstrates that homosporous pteridophytes are not highly inbreeding as previously suggested.     

A solution to the human paradox: fundamental ontogenies and heterochronies

Solving the human paradox means explaining how a genetic difference of a mere 1% can be consistent with 5 million years of anatomical transformation from great apes to present-dayHomo sapiens. The solution proposed here is that of the internal history of ontogenetic change. A concept of “fundamental ontogeny” is developed and deduced from comparison between living and fossil primates. The fossil human lineage can be summarized into five fundamental ontogenies corresponding to successive skull plans (bauplans) resulting from five major phases of craniofacial contraction: prosimians (adapiforms), monkey apes (propliopithecidae), great apes (dryopithecidae), australopithecines andHomo. The morphological areas defined by these skull plans include more-or-less numerous species. This concept leads to renewed debate about (i) the relationship between speciation and bauplans, and (ii) the mechanisms involved in the successive steps of cranio-facial contraction and the correlated morphological changes. It is suggested that, from great apes to modern man, numerous heterochronies (hypermorphosis, hypomorphosis and post-displacements) have occurred during ontogeny, allowing the acquisition of permanent bipedalism inAustralopithecus andHomo, the increased cranial capacity of primitive forms ofHomo, and the disappearance of simian characters associated with renewed increase in cranial capacity inH. sapiens.     

Heel contact as a function of substrate type and speed in primates

In this report we provide detailed data on the patterns and frequency of heel contact with terrestrial and arboreal supports in primates. These data can help resolve the question of whether African apes and humans are uniquely “plantigrade” (Gebo [1992] Am. J. Phys. Anthropol. 89:29–58; Gebo [1993a] Am. J. Phys. Anthropol. 97:382–385; Gebo [1993b] Postcranial Adaptation in Nonhuman Primates), or if plantigrady is common in other primates (Meldrum [1993] Am. J. Phys. Anthropol. 91:379–381). Using biplanar and uniplanar videotapes, we recorded the frequency and timing of heel contact for a variety of primates (32 species) walking on the ground and on simulated arboreal supports at a range of natural speeds. Our results indicate that Pongo as well as the African apes exhibit a “heel-strike” at the end of swing phase. Ateles and Hylobates make heel contact on all supports shortly after mid-foot contact, although spider monkeys do so only at slow or moderate speeds. Data available from uniplanar videotapes suggest that this pattern occurs in Alouatta and Lagothrix as well. No other New or Old World monkey or prosimian in this study made heel contact during quadrupedalism on any substrate. Thus, heel contact occurs in all apes and atelines, but only the great apes exhibit a heel-strike. We suggest that heel contact with the substrate is a by-product of an active posterior weight-shift mechanism involving highly protracted hindlimbs at touchdown. Force plate studies indicate that this mechanism is most extreme in arboreally adapted primate quadrupeds walking on arboreal supports. Although heel contact and heel-strike may have no evolutionary link, it is possible that both patterns are the result of a similar weight shift mechanism. Therefore, the regular occurrence of heel contact in a variety of arboreal primates, and the absence of a true biomechanical link between limb elongation, heel contact, and terrestriality, calls into question the claim that hominid foot posture was necessarily derived from a quadrupedal terrestrial ancestor. © 1995 Wiley-Liss, Inc.     

Knuckle-walking and the evolution of hominoid hands

Knuckle-walking is a pattern of digitigrade locomotion unique to African apes among Primates. Only chimpanzees and gorillas are specially adapted for supporting weight on the dorsal aspects of middle phalanges of flexed hand digits II–V. When forced to the ground, most orangutans assume one of a variety of flexed hand postures, but they cannot knuckle-walk. Some orangutans place their hands in palmigrade postures which are impossible to African apes. The knuckle-walking hands and plantigrade feet of African apes are both morphologically and adaptively distinct from those of Pongo, their nearest relative among extant apes. These features are associated with a common adaptive shift to terrestrial locomotion and support placing chimpanzees and gorillas in the same genus Pan. It is further suggested than Pan comprises the subgenera (a) Pan, including P. troglodytes and pygmy chimpanzees, and (b) Gorilla, including mountain and lowland populations of P. gorilla. African apes probably diverged from ancestral pongids that were specially adapted for distributing their weight in terminal branches of the forest canopy. Early adjustments to terrestrial locomotion may have involved fist-walking which later evolved into knuckle-walking. Orangutans continued to adapt to feeding and locomotion in the forest canopy and their hands and feet became highly specialized for four-digit prehension. Although chimpanzees retained arboreal feeding and nesting habits, they moved from tree to tree by terrestrial routes and became less restricted in habitat. While adapting to a diet of ground plants gorillas increased in size to the point that arboreal nesting is less frequent among them than among chimpanzees and orangutans. Early hominids probably diverged from pongids that had not developed prospective adaptations to knuckle-walking, and therefore did not evolve through a knuckle-walking stage. Initial adjustments to terrestrial quadrupedal locomotion and resting stance probably included palmigrade hand posturing. Their thumbs may have been already well developed as an adaptation for grasping during arboreal climbing. A combination of selection pressures for efficient terrestrial locomotor support and for object manipulation further advanced early hominid hands toward modern human configuration.     

Standardization of the twinning rate

There is a great interest in comparing twinning rates. These comparisons can be performed between different time periods for a specific population, between different regions within the same country, and between different populations. However, there are several factors (maternal age, parity, urbanization, etc.) that influence the twinning rate. The most dominant one is maternal age, and because the age distribution of the mother varies, it is necessary to standardize the data to make these comparisons. If we want to compare the twinning rates in different countries, we have to face the problem that the composition of the data from different countries may differ to a great extent. The applicable method is determined by the data of the lowest quality. Often the available data do not allow the traditional (direct and/or indirect) methods of standardization. Under such circumstances other methods have to be used. Earlier, Fellman and Eriksson (1987) proposed and successfully applied a new method. In this article we discuss the standardization problem in more detail. We suggest different methods and apply them to different data on twinning from Australia, Finland, and Baden-Württemberg (West Germany). The new standardization methods give standardized twinning rates similar to the rates obtained by traditional methods. It is noted that, irrespective of standardization method, changes in maternal age alone cannot explain temporal or regional variations in the twinning rate. Other factors that may raise or lower the twinning rate are decreasing parity, sociodemographic changes with increased communication, which causes the breakup of isolates, and deteriorating physical condition of mothers as a result of increased industrialization and urbanization.     

Subacromial Space in African Great Apes and Subacromial Impingement Syndrome in Humans

The subacromial space is the anatomical region limited superiorly by the acromion and the coracoacromial ligament and inferiorly by the glenoid fossa and the humeral head. In humans, the main tissues that form it and that can be affected by subacromial impingement syndrome are the subacromial bursa and the supraspinatus tendon. The syndrome is the most common degenerative pathology affecting the human shoulder, and it is characterized by an uncertain etiopathogenesis. We compared different anatomical parameters of the scapula related to the subacromial impingement syndrome in humans, between modern humans and 2 species of African apes (Pan troglodytes and Gorilla gorilla). The 3 species we studied are orthograde primates and they present a similar structural pattern of the scapula and subacromial space, but anatomical differences exist owing to different types of locomotion used. The main differences indicate that African apes present a more curved and tilted acromion than humans, which does not, however, imply a difference in the relative size of the subacromial space among the 3 species studied. Humans also have a lower value of the relative size of the supraspinatus fossa than African great apes, and in human females have a relative lower value than males. We studied the anatomical structures of the shoulder in African apes that researchers have related to subacromial syndrome in humans to achieve a better understanding of the etiopathogenesis of the syndrome.     

Revisiting dental fluctuating asymmetry in neandertals and modern humans

Previous studies have suggested that Neandertals experienced greater physiological stress and/or were less capable of mitigating stress than most prehistoric modern human populations. The current study compares estimates of dental fluctuating asymmetry (DFA) for prehistoric Inupiat from Point Hope Alaska, the Late Archaic, and Protohistoric periods from Ohio and West Virginia, and a modern sample from Ohio to Neandertals from Europe and Southwest Asia. DFA results from developmental perturbation during crown formation and is thus an indicator of developmental stress, which previous studies have found to be higher in Neandertals than in several modern human populations. Here, we use recent methodological improvements in the analysis of fluctuating asymmetry suggested by Palmer and Strobeck (Annu Rev Ecol Syst 17 ( 1986 ) 391–421, Developmental instability: causes and consequences ( 2003a ) v.1–v.36, Developmental instability: causes and consequences ( 2003b ) 279–319) and compare the fit of Neandertal DFA Index values with those of modern humans. DFA estimates for each of the modern population samples exceeded measurement error, with the Inupiat exhibiting the highest levels of DFA for most tooth positions. All significant Neandertal z‐scores were positive, exceeding the estimates for each of the modern prehistoric groups. Neandertals exhibited the fewest significant differences from the Inupiat (9.2% of values are significant at P < 0.05), while for the other modern prehistoric groups more than 10% of the Neandertal z‐scores are significant at P < 0.05, more than 90% of these significant scores at P < 0.01. These results suggest that the Inupiat experienced greater developmental stress than the other prehistoric population samples, and that Neandertals were under greater developmental stress than all other prehistoric modern human samples. Am J Phys Anthropol 149:193–204, 2012. © 2012 Wiley Periodicals, Inc.     

Enamel hypoplasia in deciduous teeth of great apes: do differences in defect prevalence imply differential levels of physiological stress?

This paper presents new data on enamel hypoplasia in the deciduous canine teeth of great apes. The enamel defect under consideration is known as localized hypoplasia of primary canines (LHPC), and is characterized by an area of thin or missing enamel on the labial surface of deciduous canine teeth (Skinner [1986a] Am. J. Phys. Anthropol. 69:59-69). Goals of this study are: 1) to determine if significant differences in the frequency of LHPC occur among three genera of great apes, and 2) to evaluate variation in LHPC prevalence among great apes as evidence of differential physiological stress. Infant and juvenile apes with deciduous teeth were examined at the Cleveland Museum of Natural History (n = 100) and at the Smithsonian Institution, National Museum of Natural History (n = 36). Deciduous teeth were observed under oblique incandescent light, with the naked eye and with a 10x hand lens. Enamel hypoplasia was scored using Federation Dentaire International (FDI)-Defects of Dental Enamel (DDE) standards. Hypoplasias were recorded by drawing defect location and size on a dental chart, and by measuring defect size and location with Helios needlepoint dial calipers. The prevalence of LHPC is reported by genus and sex, using two approaches: 1) the frequency of affected individuals-those having one or more deciduous canine teeth scored positive for LHPC; and 2) the number of canine teeth scored positive for LHPC as a percentage of all canine teeth observed. Variation in defect size and location will be described elsewhere. Localized hypoplasia of primary canine teeth was found in 62.5% of 128 individual apes, and in 45.5% of 398 great ape deciduous canines. As in humans, LHPC is the most common form of enamel hypoplasia in deciduous teeth of great apes, while LEH is rare or absent. The distribution and pattern of expression of LHPC in great apes is similar to that described in humans: side differences are not significant, but mandibular canines exhibit the defect two to five times more often than maxillary canine teeth. Differences in LHPC prevalence by sex are small and not significant. Intergeneric differences are large and non-random: chimpanzees (Pan) exhibit a significantly lower frequency of LHPC (22%, n = 50) by individual count, than either the orangutan (Pongo, 88.0%, n = 25) or the gorilla (Gorilla, 88.7%, n = 53). Tooth count prevalences exhibit a similar pattern of variation and are also statistically significant. These findings suggest that large bodied great apes (gorilla and orangutan) may be under greater physiological stress during perinatal and early postnatal development than the chimpanzee. The size, position, and timing of LHPC lesions are currently under analysis and may yield more insight into the etiological origin of this enamel defect.