American journal of physical anthropology最新文献

Urine marking has been neglected in prosimian primates. Captive studies showed that the Malagasy prosimian Lemur catta scent marks with urine, as well as via specialized depositions. L. catta urine mark, a multimodal signal, differs from simple urination in terms of different design features, including tail configuration: the tail is held up during marking (UT-up) and down during urination (UT-down). We explore economy and function of UT-up in the female dominant L. catta. We collected 240 h of observations on one group at Berenty (south Madagascar) during the nonmating period via all occurrences sampling. We gathered behavioral bouts/contexts (marking, traveling, feeding, resting, and fights) and recorded 191 UT-ups and 79 UT-downs. Via Global Positioning System we established the location of the places frequented i) by extragroup individuals and ii) by group members, in this case recording also behavioral context and time spent in each place. We found that L. catta UT-up is not an artifact of captivity. Moreover, UT-up in the nonmating period plays a role in territorial defense, which is mostly performed by females in L. catta society. Female UT-ups were the most investigated and UT-ups were performed/investigated more by females. Finally, signal use is parsimonious, in that urine is economically placed where and when detection probability by competitors is higher. UT-ups were performed in places most frequented by extragroup individuals and in presence of extragroup competitors (nonrandom topography and timing). In conclusion, we suggest that UT-up is an economical signal with a primarily territorial function.

In some primate species, pelage colorations at birth contrast with adult colorations. The intensity of natal coats and their phylogenetic distribution is highly variable within primates. Natal coat coloration seems to change to adult coloration in most species when infants become independent from their mothers, but an accepted functional explanation for natal coats is not available. Here we describe pelage coloration change in sexually dichromatic redfronted lemurs (Eulemur fulvus rufus) in Kirindy Forest, and propose a new functional hypothesis for this phenomenon. In this species, infants are born with adult male coloration and female infants subsequently undergo a change in coloration. Using digital pictures and behavioral data collected on eight mother-offspring dyads from birth until the end of the coloration change, we 1) described timing and pattern of pelage developmentin redfronted lemur infants and 2) examined behavioral developmental correlates of the coloration change. The color change took place between 7 and 17 weeks of age and coincided with advanced physical independence; a pattern also found in monochromatic primate species with natal coats. No behavioral differences between male and female infants were found. Hypotheses about the ultimate function of natal coats focusing on enhanced infant care or reduced infanticide risk did not explain the pelage change in redfronted lemurs. The natal pelage pattern in this species may instead serve as sexual mimicry. Accordingly, female infants may mimic males during the most vulnerable developmental phase to avoid sex-specific aggression by adult females in a species with intense female-female aggression and competition.

The purpose of this study was to investigate the impact of economic and cultural change on immune function and psychosocial stress in an indigenous Siberian population. We examined Epstein-Barr virus antibodies (EBV), an indirect biomarker of cell-mediated immune function, in venous whole blood samples collected from 143 Yakut (Sakha) herders (45 men and 98 women) in six communities using a cross-sectional study design. We modeled economic change through the analysis of lifestyle incongruity (LI), calculated as the disparity between socioeconomic status and material lifestyle, computed with two orthogonal scales: market and subsistence lifestyle. EBV antibody level was significantly negatively associated with both a market and a subsistence lifestyle, indicating higher cell-mediated immune function associated with higher material lifestyle scores. In contrast, LI was significantly positively associated with EBV antibodies indicating lower immune function, and suggesting higher psychosocial stress, among individuals with economic status in excess of material lifestyle. Individuals with lower incongruity scores (i.e., economic status at parity with material resources, or with material resources in excess of economic status) had significantly lower EBV antibodies. The findings suggest significant health impacts of changes in material well-being and shifting status and prestige markers on health during the transition to a market economy in Siberia. The findings also suggest that relative, as opposed to absolute, level of economic status or material wealth is more strongly related to stress in the Siberian context.

Developmental and structural affinities between modern human and Neanderthal dental remains continue to be a subject of debate as well as their utility for informing assessments of life history and taxonomy. Excavation of the Middle Paleolithic cave site Lakonis in southern Greece has yielded a lower third molar (LKH 1). Here, we detail the crown development and enamel thickness of the distal cusps of the LKH 1 specimen, which has been classified as a Neanderthal based on the presence of an anterior fovea and mid-trigonid crest. Crown formation was determined using standard histological techniques, and enamel thickness was measured from a virtual plane of section. Developmental differences include thinner cuspal enamel and a lower periodicity than modern humans. Crown formation in the LKH 1 hypoconid is estimated to be 2.6-2.7 years, which is shorter than modern human times. The LKH 1 hypoconid also shows a more rapid overall crown extension rate than modern humans. Relative enamel thickness was approximately half that of a modern human sample mean; enamel on the distal cusps of modern human third molars is extremely thick in absolute and relative terms. These findings are consistent with recent studies that demonstrate differences in crown development, tissue proportions, and enamel thickness between Neanderthals and modern humans. Although overlap in some developmental variables may be found, the results of this and other studies suggest that Neanderthal molars formed in shorter periods of time than modern humans, due in part to thinner enamel and faster crown extension rates.

Since its discovery in southeastern Uzbekistan in 1938, the Teshik-Tash child has been considered a Neandertal. Its affinity is important to studies of Late Pleistocene hominin growth and development as well as interpretations of the Central Asian Middle Paleolithic and the geographic distribution of Neandertals. A close examination of the original Russian monograph reveals the incompleteness of key morphologies associated with the cranial base and face and problems with the reconstruction of the Teshik-Tash cranium, making its Neandertal attribution less certain than previously assumed. This study reassesses the Neandertal status of Teshik-Tash 1 by comparing it to a sample of Neandertal, Middle and Upper Paleolithic modern humans, and recent human sub-adults. Separate examinations of the cranium and mandible are conducted using multinomial logistic regression and discriminant function analysis to assess group membership. Results of the cranial analysis group Teshik-Tash with Upper Paleolithic modern humans when variables are not size-standardized, while results of the mandibular analysis place the specimen with recent modern humans for both raw and size-standardized data. Although these results are influenced by limitations related to the incomplete nature of the comparative sample, they suggest that the morphology of Teshik-Tash 1 as expressed in craniometrics is equivocal. Although, further quantitative studies as well as additional sub-adult fossil finds from this region are needed to ascertain the morphological pattern of this specimen specifically, and Central Asian Middle Paleolithic hominins in general, these results challenge current characterizations of this territory as the eastern boundary of the Neandertal range during the Late Pleistocene.

Body size may be an important factor influencing the evolution of facial expression in anthropoid primates due to allometric constraints on the perception of facial movements. Given this hypothesis, I tested the prediction that observed facial mobility is positively correlated with body size in a comparative sample of nonhuman anthropoids. Facial mobility, or the variety of facial movements a species can produce, was estimated using a novel application of the Facial Action Coding System (FACS). I used FACS to estimate facial mobility in 12 nonhuman anthropoid species, based on video recordings of facial activity in zoo animals. Body mass data were taken from the literature. I used phylogenetic generalized least squares (PGLS) to perform a multiple regression analysis with facial mobility as the dependent variable and two independent variables: log body mass and dummy-coded infraorder. Together, body mass and infraorder explain 92% of the variance in facial mobility. However, the partial effect of body mass is much stronger than for infraorder. The results of my study suggest that allometry is an important constraint on the evolution of facial mobility, which may limit the complexity of facial expression in smaller species. More work is needed to clarify the perceptual bases of this allometric pattern.

The Homo habilis OH 62 partial skeleton has played an important, although controversial role in interpretations of early Homo locomotor behavior. Past interpretive problems stemmed from uncertain bone length estimates and comparisons using external bone breadth proportions, which do not clearly distinguish between modern humans and apes. Here, true cross-sectional bone strength measurements of the OH 62 femur and humerus are compared with those of modern humans and chimpanzees, as well as two early H. erectus specimens-KNM-WT 15000 and KNM-ER 1808. The comparative sections include two locations in the femur and two in the humerus in order to encompass the range of possible section positions in the OH 62 specimens. For each combination of section locations, femoral to humeral strength proportions of OH 62 fall below the 95% confidence interval of modern humans, and for most comparisons, within the 95% confidence interval of chimpanzees. In contrast, the two H. erectus specimens both fall within or even above the modern human distributions. This indicates that load distribution between the limbs, and by implication, locomotor behavior, was significantly different in H. habilis from that of H. erectus and modern humans. When considered with other postcranial evidence, the most likely interpretation is that H. habilis, although bipedal when terrestrial, still engaged in frequent arboreal behavior, while H. erectus was a completely committed terrestrial biped. This adds to the evidence that H. habilis (sensu stricto) and H. erectus represent ecologically distinct, parallel lineages during the early Pleistocene.

The Northern Talysh from Azerbaijan and the Southern Talysh from Iran self-identify as one ethnic group and speak a Northwestern Iranian language. However, the Northern and Southern Talysh dialects are so different that they may actually be separate languages. Does this linguistic differentiation reflect internal change due to isolation, or could contact-induced change have played a role? We analyzed mtDNA HVI sequences, 11 Y-chromosome bi-allelic markers, and 9 Y-STR loci in Northern and Southern Talysh and compared them with their neighboring groups. The mtDNA data show a close relatedness of both groups with each other and with neighboring groups, whereas the Northern Talysh Y-chromosome variation differs from that of neighboring groups, probably as a result of genetic drift. This genetic drift most likely reflects a founder event in the male gene pool of Northern Talysh: either fewer males than females migrated to Azerbaijan, or there was a higher degree of relatedness among the male migrants. Since we find no evidence of substantial genetic contact between either Northern or Southern Talysh and neighboring groups, we conclude that internal change, rather than contact-induced change, most likely explains the linguistic differentiation between Northern and Southern Talysh.

We examined thermoregulatory behaviors in a wild population of white-faced capuchins (Cebus capucinus) inhabiting a highly seasonal dry forest in Santa Rosa National Park (SRNP), Costa Rica. The dry season in SRNP lasts approximately 5 months and is characterized by high ambient temperatures regularly exceeding 37 degrees C, low relative humidity, and the near absence of precipitation. This study demonstrates that capuchins rest more and travel shorter distances during the hottest and driest hours of the day, and suggests that they extend their tongues to lower body temperature via evaporative cooling. Seasonal weather patterns and group movement data reported here are based on 940 h of observations on three social groups of capuchins (wet season: 370 h, dry season: 570 h). In the dry season, the proportion of time spent resting increased at higher temperatures whereas the proportion of time spent traveling decreased. Distance traveled between location points taken at half-hour intervals decreased significantly as temperature increased, although the correlation was not strong. Capuchins exposed their tongues during hot, dry, windy conditions, and this behavior was much more frequent in the dry season. Temperature was significantly higher and humidity significantly lower for "tongue-out" events than expected for a random event in the dry season. Finally, as surface water became scarce, home-range areas of heavy use became increasingly centered on the remaining permanent water sources. These results suggest that heat stress and water scarcity are significant influences on the behavior of capuchins in hot, dry conditions.