File Name: hiiemae kay 1974 jaw movement and tooth use in recent and fossil primates .zip
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Microscopic tooth wear studies on primates have largely focused on interspecific dietary comparisons, while few have addressed intraspecific variations, such as those among age groups. Here, we examined to what extent dietary shifts during ontogeny can be revealed from microscopic tooth wear in a western chimpanzee population using 3D surface texture 3DST analysis.
We expected to find an age-dependent increase in texture complexity resulting from the more frequent consumption of seeds and insects in older compared to younger individuals.
Furthermore, we expected the introduction of phytolith-producing plants to the diet of post-weaned individuals to result in many small and parallel-orientated 3DST features in juveniles, adolescents and adults compared to infants. We found that the 3DST pattern did not mirror the observed increase in dietary breadth from infants to adults. However, we found that age-dependent differences in the consumption of phytolith-producing plants were reflected to some extent in the 3DST pattern: infants and adolescents who spent more time feeding on phytolith-producing plants than older individuals had more parallel orientated 3DSTs with higher peaks, while adults had flatter and more randomly orientated 3DST features.
Our results suggest that phytoliths as small abrasive particles may be of greater importance for the 3DST formation than food categories, such as fruits, leaves or seeds. However, compared to the variation in the feeding data, 3DST results show only little variation among age groups. We conclude that 3DST does not explicitly reflect ontogenetic dietary changes in chimpanzees.
Rather, other factors, such as individual- or sex-based feeding habits as well as seasonal variation in dust accumulation, may be of greater importance for 3DST formation. The diet of chimpanzees Pan troglodytes includes mostly fruits, but also leaves, piths and other vegetative plant parts as well as animal resources e.
This dietary diversity partly arises from the fact that four subspecies of chimpanzees have been recognized Wilson and Reeder, ; Oates et al. While western chimpanzees P. Nigeria-Cameroon chimpanzees P. Other than the reported differences in fruit content in the diet among chimpanzee subspecies, several authors have reported age-related feeding preferences within populations as well e.
Such feeding preferences change throughout a chimpanzee's life, but they seem to be strongest early in life. Thus, infant chimpanzees introduce solid food to their diet at an age of around 4—5 months Hiraiwa-Hasegawa, a , which almost exclusively consists of ripe fruit Smith et al. At an age of around 1. This process is accompanied by dietary transitions, such as the introduction of new food items or changes in dietary proclivities. For example, infant eastern chimpanzees up to 5 years of age of the Mahale mountains Tanzania consume more young leaves and fewer matures leaves compared to their mothers Hiraiwa-Hasegawa, a , but in general they increase their feeding time on leaves between 2 and 3 years and again after 4 years of age Matsumoto, Infant eastern chimpanzees of the Kanyawara community in Kibale National Park Uganda have a narrower dietary breadth compared to adolescent and adult chimpanzees.
However, even after weaning is completed, at around 5 years of age Fahy et al. In western chimpanzees P. Furthermore, juvenile chimpanzees 5—10 years of age of the Kanyawara community were observed to feed more often on ripe fruits than their mothers Bray et al. In addition, a continuous increase in the feeding bouts on seed-rich Ficus fruits until an age of 10—13 years was documented Bray et al. In Mahale, adolescent male chimpanzees feed less often on piths than adult males Uehara, Additionally, certain feeding behaviors e.
It has been shown that the efficiency with which these foods can be accessed increases with age. For example, western chimpanzees begin to crack nuts efficiently at an age of 4 years Boesch and Boesch-Achermann, Moreover, hunting and meat consumption is mainly observed in adult male chimpanzees; they only reluctantly share meat with adult females and young individuals Boesch, ; Boesch and Boesch-Achermann, Gathering data about feeding behavior and dietary proclivities during ontogeny can provide knowledge about somatic development, cognitive abilities and life history events.
However, it is not always possible to obtain direct evidence, such as from focal observations or the analysis of food remains and fecal samples. An alternative approach to inferring the diet of an individual is dental microwear. This method is related to the examination of microscopic signatures on tooth wear facet surfaces that form and modify during an individual's life as the result of tooth use. Microwear signatures have traditionally been described two-dimensionally 2D as pits and scratches Gordon, ; Teaford and Robinson, Gordon analyzed 2D wear patterns in western chimpanzees and found that juveniles had a higher density of pits and scratches compared to adults.
She proposed that diet might be not the factor explaining these differences since the dietary variation within one species is supposed to be small. Rather, she speculated that a varying enamel hardness between younger and older individuals could have led to distinct pit and scratch densities among age groups Gordon, She proposed that the higher density of microwear features in juveniles might be linked to decreasing enamel hardness in older individuals, since longer exposure to wear might lead to softer inner enamel layers and microwear features are more easily erased or reworked.
The authors argued that these higher scratch densities in infants could be indicative of an abrasive diet, which is accompanied by early weaning. For example, the latter allows for the quantification of various geometric aspects, such as surface height, feature density, and surface complexity. Other than microwear signatures caused by internal dietary abrasives, external dust or grit ingested together with the diet may contribute to wear e. To that end, we compare data from feeding observations to 3DST analysis data measured on deciduous premolars dp4 and permanent molars M1 and M2.
While microwear studies frequently have concentrated on M1s and M2s it is unclear whether both permanent and deciduous teeth carry similar microwear signals.
However, combining teeth would not only contribute to an elevated sample size but also enable to include younger individuals to discover possible dietary transitions during early ontogeny. Furthermore, it has been shown that differences in microwear signals between facet types phase I vs. While in hard-object feeders the dietary signal is more pronounced on phase II facets, in primates with a versatile diet both phase II and phase I facets reflect the diet Krueger et al.
To test for the relationship of diet and 3DST data we use two sets of predictions. First, we predict that if the dietary composition, especially of more challenging food parts hard objects like seeds and insect cuticles Strait, ; Scott et al.
For example, fig fruits as a common part of a chimpanzee's diet are an assembly of drupes with a high amount of rather small seeds 1—2 mm per fruit, while other seeds, such as seeds of Calpocalyx sp. An increase in the amount of such hard objects in the diet has been shown to correlate with an increase in surface texture complexity Ramdarshan et al. Kaiser et al. Consequently, if juveniles fed mainly on soft ripe fruits and young leaves, we expect to observe less complex, voluminous and isotropic wear facet surfaces combined with shallower dales or valleys.
Furthermore, if the proportion of fig fruits including their small seeds and other large hard particles e. In addition to the above described millimeter-sized hard objects, there are micrometer-sized instrinsic abrasive particles in several monocotyledonous and dicotyledonous plant families, known as phytoliths Mercader et al. Therefore, we predict that if infants have a reduced ingestion of phytoliths, their surface texture should clearly differ from juveniles, adolescents and adults.
Thus, we expect the surface textures of infants to have less dales and valleys as well as more plateau-like features due to the reduced amount of small abrasive particles in the diet, while we expect to find the opposite in adolescents and adults.
We analyzed a total of 79 molars [upper and lower deciduous fourth premolars dp4 , permanent first M1 , and second molars M2 ] from 41 chimpanzees P. Feeding sequences were available for a period of up to 12 days prior to death of these individuals and fall within the range of the suggested duration of microwear formation for primates Teaford and Oyen, Raw data of adult chimpanzee feeding observations were taken from Schulz-Kornas et al.
We used two sets of food categorization to describe the feeding behavior. We distinguished between food categories with potential hard objects e. Second, we classified the plant parts consumed based on presence or absence of phytoliths Supplemental Data Table S2. For plants not included in the study by Power et al. Here, we only added plants to the phytolith-producing plant group if they were classified as a high-producing plant see Table 1.
We exclusively selected teeth which exhibited occlusal surfaces with slight to moderate wear, i. Moreover, selected wear facets were clearly delimited from neighboring wear facets. We analyzed 3DSTs on facet 9 which is the standard phase II facet for primate dietary reconstructions. This facet is located on the buccal and slightly posterior facing slope of the protocone of upper molars, and on the lingual facing slope of the hypoconulid of lower molars Kay and Hiiemae, ; Kay, ; Maier and Schneck, Additionally, we analyzed the buccal phase I facet 3, which is located on the lingual slope of the paracone, and the buccal and slightly mesial facing slope of the hypoconulid Kay and Hiiemae, ; Maier and Schneck, Following the procedure of Schulz et al.
For specimens with deciduous dentition we exclusively molded and analyzed the dp4 also known as the second deciduous molar , because of their similar morphology and facet location to permanent molars Swindler, The measurement routine was performed according to Schulz et al.
The resolution in x and y were 0. The statistical analyses were performed using the open-source software R 3. The test-statistics were conducted following the suggestions of Calandra et al.
According to Calandra et al. The WYT tests whether at least one of the groups infants, juveniles, adolescents or adults has a different mean than the other groups. Whenever a significant difference was found, a heteroscedastic pair-wise test was subsequently employed to reveal the source of difference. However, the p -values in this test are not controlled for the so-called family-wise error. Therefore, the heteroscedastic rank based test was performed to control for the family-wise error via Hochberg's method.
This test computes, for all pairs of groups, the probability that an observation from one group is smaller than from another group. The R packages xlsx version 0. Group-wise comparison was conducted to test for variation between tooth type deciduous vs. The tooth type comparison was only conducted on five juveniles, where both the dp4 and the M1 were fully erupted and present in the same specimen see Supplemental Data Table S1.
For the age group comparison we analyzed specimens that had died during wet and dry periods. Additionally, we selected 17 3DST parameters that fit our predictions but were not affected by seasonality in a previous study on 3DSTs in the same population Schulz-Kornas et al. Finally, we performed a Factor Analysis FA to compare the effect of facet type f9 vs. We selected the 13 3DST parameters due to following criteria: no missing values and approximately normal distribution.
For all analyses, upper and lower teeth were analyzed separately. Of the permanent molars, the first molar was the preferred tooth. If the first molar was not available, then the second permanent molar was used to increase the number of specimens.
The two major dietary classifications to describe the feeding behavior in each group are shown in Figure 1A for food categories and Figure 1B for phytolith production by different plants. Figure 1. Mean daily feeding duration on A food categories and B phytolith-producing plants among age groups.
In general, monocotyledons and animal resources were relatively rare in all age groups. Feeding on monocotyledons and animal resources mammals, insects was absent in infants. Individuals of all age groups spent most of their time feeding on dicotyledonous plants, which vary in the production of phytoliths Supplemental Data Table S2.
We analyzed upper dp4 and M1 in individuals with mixed dentition see Supplemental Data Table S1 to test for tooth type specific wear signatures.
The objective of this article was to describe the relationship between the movement of the interincisive point and the working temporomandibular joint condyle with regard to the horizontal plane during laterality movements. Clinical records of patients complaining of temporomandibular joint disorder for whom axiographic examination had been performed were searched and analyzed retrospectively at a private practice. Only patients showing an asymmetrical gothic arch with retrusive lateral excursion in an absolute sense with respect to the frontal plane or with respect to the contralateral laterality were selected. Sixty-six clinical records of patients who had undergone axiographic examination were found. A total of 37 patients met the inclusion criteria and were included in the study.
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Jaw movement and tooth use in recent and fossil Primates. March ; American Journal of Physical Anthropology 40(2) DOI: /ajpa. F. KAY. AND. K. M. HIIEMAE. sults on the slopes of cusps, behind the.Reply
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Microscopic tooth wear studies on primates have largely focused on interspecific dietary comparisons, while few have addressed intraspecific variations, such as those among age groups.Reply