Although studies of population affinity based on nonmetric traits have achieved remarkable successes, most of these studies seem to present a methodological problem. Since evidence indicates a threshold model for most nonmetric traits, the use of individual counts in studies would seem to have wasted a considerable amount of useful information to produce less reliable results. A review of relevant articles suggests that the use of this baseless methodology has persisted by neglecting an inconvenient truth. To improve the situation, the author proposes a generalized theory based on the assumption of constant within-individual instabilities, which covers both the standard threshold model and the single-genotype model. The proposed theory proves the general validity of Ossenberg’s proposals, i.e. the use of side counts for threshold traits and an examination of etiology by correlating the proportion of asymmetry and the trait frequency. The data of 28 nonmetric traits collected by Ossenberg were examined using the theory. The proportion of asymmetry was negatively correlated with side counts in all the traits with statistical significance. The threshold model exhibited higher goodness of fit than the single-genotype model for 25 traits. The loss of information caused by using individual counts for threshold traits instead of side counts is estimated to be equivalent to a considerable decrease (16–40%) in sample size. The use of both sides improves the reliability of the tetrachoric estimation of inter-trait correlation comparable to a 1.6- to 2.6-fold increase in the sample size by enabling the use of their four combinations. It was also shown that the theory makes it possible to estimate the penetrance rate of congenital anomalies and tumors from the proportion of asymmetry.
The olfactory receptor (OR) gene family is comprised of hundreds of intact and disrupted genes in humans. The compositions and copy number variation (CNV) of disrupted and intact OR genes among individuals is expected to cause variation in olfactory perception. However, little is known about OR genetic variation in many human populations. In this study, we used targeted capture enrichment and massive parallel short-read sequencing methods to examine genetic variation of OR genes, as well as of neutral genome regions as references, for 69 anonymized unrelated Japanese individuals. The capture probes were designed for 398 intact OR genes in the human reference genome hg38, and 85 neutral references. Probes were also designed for four unannotated and 99 ‘nearly-intact’ (hg38-pseudo) OR genes in hg38 and 53 chimpanzee OR genes in the Pantro3.0 genome database with no orthologs in hg38. All the hg38 OR genes and one Pantro 3.0 OR gene were retrieved. The mean sequencing depth was significantly higher than that of the 1000 Genomes Project. A total of 30 OR genes from hg38-intact and hg38-pseudo categories were newly found to be segregating pseudogenes. One hg38-pseudo OR gene was intact in all individuals. CNV was detected in 63 OR genes. Tajima’s D analysis for OR genes and neutral references was consistent with balancing selection to maintain allelic differences in intact OR genes. These results demonstrate that the targeted capture by probes with diversity-oriented design is far more effective than a whole-genome approach to retrieve OR genes and achieve high-depth sequencing and thus to reveal polymorphisms for the OR multigene family. The composition of OR genes in the human reference genome hg38 does not necessarily represent those in many humans, implying higher perceptual variation than previously thought. The current study inspires further investigation with a similar approach at a global scale.
The recurrent branch of the ophthalmic artery which originates from the internal carotid artery, or the recurrent meningeal artery (RMA), often extends to the parietal meninges in non-human haplorrhines. The RMA usually enters the cranial cavity via the superior orbital fissure (SOF) in modern humans and generally via the cranio-orbital foramen (COF) in non-human haplorrhines. The present study aimed to clarify how often the RMA extends its territory to the parietal meninges and via which pathway it enters the cranial cavity in Indonesian Homo erectus. This study also aimed to enhance our knowledge of cranial vascular traces in modern humans. The caliber of the COF and the associated vascular trajectories were examined in 156 sides of 78 modern Japanese crania and 12 sides of eight Indonesian H. erectus specimens. The results showed that two Indonesian H. erectus crania (Sambungmacan 4 and Ngawi) had a large COF unilaterally, via which the RMA probably extended its territory to the parietal region. The prevalence of RMA reaching the parietal region in Indonesian H. erectus (16.7%) was not as high as that in the extant great apes, but significantly higher than that in Homo sapiens (0.6% in this study; 3% at most in general). These results suggest that the SOF-related RMA became predominant in H. sapiens or the ancestor sometime in the Pleistocene, while the middle meningeal artery (MMA) arising from the external carotid–maxillary artery might not have been so enhanced in H. erectus and their ancestral hominins versus modern humans. The possible Influence of encephalization and other factors on the evolutionary changes of the RMA and MMA can be hypothesized based on ontogenetic and hemodynamic assumptions.
Although early Neolithic Anatolia is a key region for the development of sedentary society by modern humans, osteological studies are limited to specimens from the later period or from other regions such as southern Levant. We examined nearly 100 human skeletal remains from Hasankeyf Höyük, a Pre-Pottery Neolithic A (PPNA) site in southeastern Anatolia, which were uncovered during an excavation between 2011 and 2015. A total of 124 individuals were identified as belonging to the Neolithic period. The adult/subadult ratio was close to 1:1, and the sex proportion was skewed towards an abundance in males. A few stature estimates fell within the variation range for Natufian and Neolithic peoples in the southern Levant and Anatolia. The estimated life expectancy was below 30, from 27 to 30 years old, based on age criteria related to dental wear stage. On the basis of dentognathic evidence, the skeletons exhibited heavy occlusal wear for their age, with a lot of obliquely slanted occlusal surfaces and enamel chipping. The observed oral health and dental abrasion patterns are discussed with regards to the people’s biological/behavioral adaptations to the environment, such as the nutritional quality of their diet, alimentary customs, or any indications that the teeth were used as a ‘third hand.’ The Hasankeyf Höyük people are considered to represent very early sedentary villagers in southeast Anatolia who would not have initiated the domestication of plants and animals.
The objective of this study was to analyze the degree of sexual dimorphism of the crania found in room 127 (tomb TT34, Thebes) and to estimate the role of morphometric dimensions in sexual dimorphism. We studied 43 female and 41 male crania. Forty-four metric measurements were taken and 31 indices were calculated. Differences were evaluated using chi-square and Student’s t-tests. A stepwise discriminant analysis with cross-validation was applied. The Sexual Dimorphism Index (SDI) indicates that the values of all variables are higher in males except for the minimum width of the nasal bones and the facial angle. The highest SDI values are observed in the bizygomatic width and in the variables that measure the size of the maxilla (palatal area). In the indices, the biggest differences are found in the craniofacial index (P < 0.001). Using variables of the neurocranium and splanchnocranium, several highly reliable discriminant functions have been obtained. The most dimorphic variables are related to regions where the cranium connects to the muscles that keep the head upright and allow tilting and rotating movements in relation to the trunk. The bizygomatic width and the external biorbital width are the most dimorphic of the facial region, differences that are justified by a greater convexity of the zygomatic arch which could be related to a hypertrophy of the temporal muscle. The width of the zygomatic arch, its robustness, and the resulting degree of sexual dimorphism may be due to dietary and/or cultural habits related to chewing and the use of the mouth as a tool.
Scientific literature frequently reports that age-at-death estimation standards developed on European and North American populations are less effective when used on genetically distant populations. Ultimately, this paper aims to inform forensic anthropologists and bioarchaeologists of the most appropriate methods to use on Southeast Asian skeletal remains by evaluating studies that have tested the replicability and accuracy of adult age estimation methods on Thai target samples. Results show that methods using the pelvis recorded the highest accuracy of up to 93%, but only when broad age ranges are used (±2 SD). Most methods produced the least bias and inaccuracy in young adults but considerably underaged older adults. Overall biases and inaccuracies tended to be lower for males than females. The sternal rib end method showed the weakest correlation with chronological age. Methods that produced age prediction developed with regression analyses derived from the Thai samples produced standard errors ranging from 9.5 to 13.9 years (using vertebrae and femora). Most of these methods were deemed too imprecise to be useful in Thai forensic cases. The best way forward to understand the wide range of morphological variation is for future studies to evaluate the influence of body size, activity patterns, socioeconomic status, nutrition, and health on skeletal aging and how it differs between Thai and geographically distant populations.
Diarrhea is among the most common causes of death in children under five years of age. Infants are particularly at risk of ingesting pathogens directly or indirectly because of their frequent oral contact with a variety of objects. In hunter-gatherer societies, the widespread use of alloparenting, in which the infant is cared for by someone other than the biological parents, may play an important role in reducing the risk of infection from oral contact in infants. This study explored the relationship between infant oral contact behavior and diarrhea as well as the effects of alloparenting on infant oral contact behavior and diarrhea in hunter-gatherer societies. We conducted an interview on infant diarrhea and a 6-hour direct observation focused on oral contact and alloparenting of 6 infants (2–28 months) and 29 caregivers (≥4 years). During the observation period, the infants had frequent contact with objects with high risk of infection, with a median of 10.5 events (range, 0–49 events), and 50% (n = 3) had diarrhea. In addition, infants mainly ate with their hands or from the hands of their caregivers, and there was no hand-washing behavior before eating, suggesting that hand-feeding may increase the risk of transmission of pathogens. Our results also showed that the number of caregivers prevented diarrhea in infants. Furthermore, alloparenting of the unique child-rearing patterns of hunter-gatherers contributed to blocking the infants’ contact with objects with high risk of infection. These study findings suggest that alloparenting may play a significant role in reducing the risks of infant diarrhea and infection by oral contact behavior, even when the risk of transmission of pathogens through oral contact among infants may be high, such as in hunter-gatherer societies.