Formation of the permanent dentition in Arikara Indians: timing differences that affect dental age assessments

This report concerns one problem encountered with application of American white dental formation standards to age assessment of sub-adults of archaeological context. Dental ages for eight mandibular permanent teeth and maxillary central and lateral incisors of Arikara Indian immature skeletons were determined according to degree of crown or root mineralization. Ages assigned to the various teeth of the same individual were compared. They showed similarities as well as patterned differences. First premolar, second premolar, and mandibular incisor ages closely approximated one another. In relation to this complex, dental ages for maxillary incisors and mandibular second molars were older by 0.5 to 1.1 years. Developmental ages assigned to individuals on the basis of third molars showed relative advancement by more than 2 years. The systematic occurrence of these observations reflects more than just individual variability; it shows the presence of population differences in tooth-formation timing. Timing differences complicate assessment of dental ages needed for growth or demographic studies.     

Comparison of two histological techniques for age determination in small cetaceans

Age estimation in odontocetes is based on counts of growth layer groups (GLGs) deposited in recording structures such as teeth. Generally, tooth sections are obtained using a cryostat microtome. However, some researchers prefer obtaining thin sections using a traditional paraffin microtome. Little information is available on the application of this technique to dolphin teeth. Our main aim was to investigate if the paraffin technique can be a viable alternative. We considered whether estimated age would be affected by preparation technique, staining method, and section thickness, while controlling for effects of species, body length, and sex. We also analyzed whether the staining method would affect readability of GLGs and age reading variability. Teeth from 86 individuals (representing seven species) were used, but not all were prepared using both techniques because sufficient teeth were not available in all cases. Although the staining method had significant effects on the estimated age using both techniques, the variability of GLG counts was small and appeared to be similar for both techniques. Using Mayer's hematoxylin stained sections of 8 μm thickness, good agreement of ages was obtained from both techniques, with more preparations classified as "good quality" for the paraffin technique. Mayer's hematoxylin provided the best contrast of the GLGs when using the paraffin technique. We conclude that the paraffin technique is viable and represents a cost-effective alternative to a cryostat microtome when preparing cetacean teeth for age determination.     

Further evaluation of physical fitness age versus physiological age in women

The present study was conducted to examine further whether adult women who are in a state of high physical fitness possess high physiological functions, and also to investigate whether those who exercise regularly are able to maintain a high quality of various physiological functions. The subjects of this study were 249 healthy Japanese adult women (aged 20–70 years). Of these subjects 30 had jogged or walked regularly for more than 3 years. The physiological ages (PA) and physical fitness ages (FA) of the individuals were estimated from 17 physiological function tests and 5 physical fitness tests, respectively, by principal components analyses. The results indicated that there was a significant correlation between PA and FA (r = 0.76, P < 0.01). To examine this relationship in more detail, the subjects were classified into three physical fitness groups (high, normal and low) based on the deviation from the regression line of FA. Comparison of the mean PA among three physical fitness groups revealed that the high physical fitness groups demonstrated a much lower PA (physiologically younger), while the low physical fitness groups showed a relatively higher PA (physiologically older) in spite of their equivalent chronological ages. From this series of studies, a new concept is proposed where different individuals have different peak physiological capacities, but that these capacities change with age at similar rates. It is suggested that interventions such as exercise and a proper diet for promoting health could increase peak functional capacity but have little effect on the rate of decline. Accepted: 3 March 1998     

Age determination by back length for African savanna elephants: extending age assessment techniques for aerial-based surveys

Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.     

Validation of scale-reading estimates of age and growth in a brown trout Salmo trutta population

In this study, we validated a scale-reading method estimating age and growth in brown trout Salmo trutta in wild, landlocked, stream-dwelling populations from mountain headwaters in the Elbe catchment area of the Czech Republic. The values estimated from scale reading were compared with measured values, collected using a mark-recapture program over eight consecutive years. The age-corrected absolute percentage error was 10.71%, primarily because the ages of the oldest individuals according to scale reading were underestimated, and the ages of juvenile individuals were slightly overestimated. The back-calculated length was slightly underestimated (the mean error was ?4.60 mm), but it was not significantly different from the real measured length. This study suggests that in cold mountain headwaters, scale reading is a sufficiently accurate method for age and growth estimation in juvenile brown trout; however, the results for adult individuals must be taken with caution.     

That awkward age for butterflies: insights from the age of the butterfly subfamily Nymphalinae (Lepidoptera: Nymphalidae)

The study of the historical biogeography of butterflies has been hampered by a lack of well-resolved phylogenies and a good estimate of the temporal span over which butterflies have evolved. Recently there has been surge of phylogenetic hypotheses for various butterfly groups, but estimating ages of divergence is still in its infancy for this group of insects. The main problem has been the sparse fossil record for butterflies. In this study I have used a surprisingly good fossil record for the subfamily Nymphalinae (Lepidoptera: Nymphalidae) to estimate the ages of diversification of major lineages using Bayesian relaxed clock methods. I have investigated the effects of varying priors on posterior estimates in the analyses. For this data set, it is clear that the prior of the rate of molecular evolution at the ingroup node had the largest effect on the results. Taking this into account, I have been able to arrive at a plausible history of lineage splits, which appears to be correlated with known paleogeological events. The subfamily appears to have diversified soon after the K/T event about 65 million years ago. Several splits are coincident with major paleogeological events, such as the connection of the African and Asian continents about 21 million years ago and the presence of a peninsula of land connecting the current Greater Antilles to the South American continent 35 to 33 million years ago. My results suggest that the age of Nymphalidae is older than the 70 million years speculated to be the age of butterflies as a whole.     

Incremental lines of dental cementum in biological age estimation

The aim of this study is to evaluate the use of counting incremental lines of dental root cementum for biological age determination, and to compare it with alternative methods. Two samples were taken: 51 teeth from 49 individuals of known age obtained at the Stomatological Clinic, Vilnius University, as well as the canine teeth from the remains of 48 individuals from the mass graves of Tuskulenai in Vilnius (inhumed 1944-47). In the latter sample, the chronological age of 43 individuals was known through personal identification. Undecalcified teeth were sectioned with the Leica SP 1600 microtome diamond saw, and incremental line count as a blind test was made on sections of 35 to 100 microns thickness. Incremental line count was possible in 82-86 percent of cases. The results of three independent counts showed that intra-observer bias has no significant impact. Biological age was estimated by adding incremental line number to the average age of tooth eruption. It was found that mean absolute error was 6.46 years for the 1st sample, 6.27 years for the 2nd sample, and in some cases exceeded 10 years. For the 2nd sample, the results were compared to those of other methods such as endocranial suture ossification, pubic symphysis morphology and the "combined" method of Nemeskéri. All four methods yield a similar correlation in regard to an individual's chronological age. The highest correlation was found for the combined method, and the lowest one for public symphysis morphology. All correlations had a similar standard error. Thus our assessment is less enthusiastic than in some past studies; it is suggested that the incremental lines rather have a similar use as other methods.     

Accuracy of dental age estimation charts: Schour and Massler,Ubelaker and the London Atlas

Dental age estimation charts are frequently used to assess maturity and estimate age. The aim of this study was to assess the accuracy of estimating age of three dental development charts (Schour and Massler, Ubelaker, and the London Atlas). The test sample was skeletal remains and dental radiographs of known‐age individuals (N = 1,506, prenatal to 23.94 years). Dental age was estimated using charts of Schour and Massler, Ubelaker, and The London Atlas. Dental and chronological ages were compared using a paired t‐test for the three methods. The absolute mean difference between dental and chronological age was calculated. Results show that all three methods under‐estimated age but the London Atlas performed better than Schour and Massler and Ubelaker in all measures. The mean difference for Schour and Massler and Ubelaker was ?0.76 and ?0.80 years (SD 1.27 year, N = 1,227) respectively and for the London Atlas was ?0.10 year (SD 0.97 year, N = 1,429). Further analysis by age category showed similar accuracy for all three methods for individuals younger than 1 year. For ages 1–18, the mean difference between dental and chronological ages was significant (P < 0.05) for Schour and Massler and Ubelaker and not significant (P > 0.05) for the London Atlas for most age categories. These findings show that the London Atlas performs better than Schour and Massler and Ubelaker and represents a substantial improvement in accuracy of dental age estimation from developing teeth. Am J Phys Anthropol 154:70–78, 2014. © 2014 Wiley Periodicals, Inc.     

Estimating age of harbor seals (Phoca vitulina) with incisor teeth and morphometrics

We compared annuli counts from sets of canine, postcanine, and incisor teeth from 450 subsistence-harvested harbor seals, submitted blind to a laboratory. Postcanine and incisor ages were highly correlated with canine age estimates ( r = 0.985 and r = 0.984, respectively), as were postcanine and incisor teeth ( r = 0.984). Age estimates from teeth of 23 known-aged seals were highly correlated; canine teeth r = 0.987; postcanine r = 0.996; incisor r = 0.992, although age for all tooth-types was underestimated for a 29-yr-old seal. Incisor estimates were variable; comparison of age estimates from two incisors/individual ( n = 42) was r = 0.992 if only high-quality age estimates were used and r = 0.705 if lower-quality estimates were used. Morphometrics and incisor-based ages of 164 live-captured seals were explored to derive a method of estimating ages of harbor seals when age estimates are needed immediately; 39 seals were of known age. Curvilinear length, mass, and axial girth were most predictive of age for females, and curvilinear length and mass for males (equations for morphometrically calculating ages are given). Morphometric-based age estimates were highly correlated with known ages ( r = 0.896) and incisor-based estimates ( r = 0.904) and discrepancies between known and morphometric-based ages were small for younger seals. Morphometric-based age estimates also accurately distinguished between young and mature individuals.     

Variation in asexual lineage age in Potamopyrgus antipodarum, a New Zealand snail

Asexual lineages are thought to be subject to rapid extinction because they cannot generate recombinant offspring. Accordingly, extant asexual lineages are expected to be of recent derivation from sexual individuals. We examined this prediction by using mitochondrial DNA sequence data to estimate asexual lineage age in populations of a freshwater snail (Potamopyrgus antipodarum) native to New Zealand and characterized by varying frequency of sexual and asexual individuals. We found considerable variation in the amount of genetic divergence of asexual lineages from sexual relatives, pointing to a wide range of asexual lineage ages. Most asexual lineages had close genetic ties (approximately 0.1% sequence divergence) to haplotypes found in sexual representatives, indicating a recent origin from sexual progenitors. There were, however, two asexual clades that were quite genetically distinct (> 1.2% sequence divergence) from sexual lineages and may have diverged from sexual progenitors more than 500,000 years ago. These two clades were found in lakes that had a significantly lower frequency of sexual individuals than lakes without the old clades, suggesting that the conditions that favor sex might select against ancient asexuality. Our results also emphasize the need for large sample sizes and spatially representative sampling when hypotheses for the age of asexual lineages are tested to adequately deal with potential biases in age estimates.     

Dental identification and age determination in Elephas maximus

The dentition of an elephant (fossil or extant) can yield clues to the animal's age species identity, provided the teeth are correctly identified. Identifying the serial category of elephant teeth is difficult because the size, shape and position of each tooth changes throughout life, as the teeth form, erupt, wear and move throught the jaw. In the present study, teeth from over 100 museum specimens of the Asian elephant ( Elephas maximus ) were the basis for establishing size ranges for cheek teeth in six serial categories (designated by Roman numerals I to VI). Although the teeth vary greatly and overlap in their dimensions, reliable identifications (as well as estimates of an individual's age in years) can be obtained using three or more measurements. An appreciation for dental variability in Elephas maximus will demand a re-evaluastion of frequently-cited examples of macroevolutionary patterns within the Elephantidae.     

Skeletal age, dental age, and the maturation of KNM-WT 15000

The skeleton of the Homo erectus boy from West Lake Turkana, Kenya (KNM-WT 15000), is remarkably complete, and this individual has thus provided a case study for several researchers examining Homo erectus growth. Using data from a longitudinal study of Montreal French-Canadian children, it is shown that while dental and skeletal ages match reasonably well at the level of a sample of children, individuals can display differences between skeletal and dental ages of 2 years or more. Furthermore, the relationship between these two markers may change over time in individual children. It is also possible to find children with patterns of dental maturation similar to KNM-WT 15000's pattern in the Montreal sample. Therefore, neither the discrepancy between skeletal age and dental age alone nor the pattern of dental maturation as assessed by dental stages precludes a human-like pattern of growth, including an adolescent growth spurt, for this individual. Some indicators (e.g., estimated body size for predicted age, and enamel formation) do suggest possible growth-patterning differences from modern humans, and therefore earlier maturation is a reasonable hypothesis, but caution is warranted, given the large degree of modern human variation in developmental markers and the inherent uncertainty in precise estimation of KNM-WT 15000's maturational parameters.     

Calibration age and quartet divergence date estimation

The date of a single divergence point--between living alligators and crocodiles--was estimated with quartet dating using calibrations of widely divergent ages. For five mitochondrial sequence datasets, there is a clear relationship between calibration age and quartet estimate--quartets based on two relatively recent calibrations support younger divergence estimates than do quartets based on two older calibrations. Some of the estimates supported by young quartets are impossibly young and exclude the first appearance of the group in the fossil record as too old. The older estimates--those based on two relatively old calibrations--may be overestimates, and those based on one old and one recent calibration support divergence estimates very close to fossil data. This suggests that quartet dating methods may be most effective when calibrations are applied from different parts of a clade's history.     

Test of histological methods of determining chronology of accentuated striae in deciduous teeth

One of the difficulties that has prevented Wilson bands, internal defects of enamel growth, from achieving maximum usefulness as indicators of stress in bioarchaeological studies is the inaccuracy of the methods for determining ages of defect occurrence. This study tests a technique that uses microstructural growth markers of enamel to establish the chronology of Wilson bands in deciduous teeth. A sample of 274 teeth from 127 subadults from an Imperial Roman necropolis was sectioned and examined under a microscope. The sample ranged in age at death from birth to 13 years. Sixty-four teeth from 50 individuals were found to have 447 Wilson bands in total. Of those contributing multiple teeth to the sample, 13 individuals had at least one Wilson band in each of two teeth that could be identified as having been formed coevally. These provided the basis for testing the methodology. Paired t-tests found no significant differences between the chronologies of matched pairs in the two teeth, with mean ages from each differing by less than 1 day. The authors propose a hypothesis that explains the development of Wilson bands, and classifies them within the context of other features of enamel. The most important implications arising from this paper are: 1) aging methods using microstructural growth markers can be applied to deciduous teeth; 2) physiological stressors leave different traces in enamel, depending on severity and time of occurrence relative to total crown development; 3) no threshold level exists; all physiological stress will leave a record; 4) therefore, no minimal definition of a Wilson band can be delineated that recognizes all such events; 5) implying that studies using them will only identify minimum rates of occurrence.     

The age and diversification of the angiosperms re-revisited

? Premise of the study: It has been 8 years since the last comprehensive analysis of divergence times across the angiosperms. Given recent methodological improvements in estimating divergence times, refined understanding of relationships among major angiosperm lineages, and the immense interest in using large angiosperm phylogenies to investigate questions in ecology and comparative biology, new estimates of the ages of the major clades are badly needed. Improved estimations of divergence times will concomitantly improve our understanding of both the evolutionary history of the angiosperms and the patterns and processes that have led to this highly diverse clade. ? Methods: We simultaneously estimated the age of the angiosperms and the divergence times of key angiosperm lineages, using 36 calibration points for 567 taxa and a "relaxed clock" methodology that does not assume any correlation between rates, thus allowing for lineage-specific rate heterogeneity. ? Key results: Based on the analysis for which we set fossils to fit lognormal priors, we obtained an estimated age of the angiosperms of 167-199 Ma and the following age estimates for major angiosperm clades: Mesangiospermae (139-156 Ma); Gunneridae (109-139 Ma); Rosidae (108-121 Ma); Asteridae (101-119 Ma). ? Conclusions: With the exception of the age of the angiosperms themselves, these age estimates are generally younger than other recent molecular estimates and very close to dates inferred from the fossil record. We also provide dates for all major angiosperm clades (including 45 orders and 335 families [208 stem group age only, 127 both stem and crown group ages], sensu APG III). Our analyses provide a new comprehensive source of reference dates for major angiosperm clades that we hope will be of broad utility.     

A review of the age determination of mammals by means of teeth, with especial reference to Africa

A growing requirement exists to determine the ages of the larger African mammals, concomitant with increasing management. Teeth offer the most practicable means of age determination, but no wholly reliable method, based on teeth, has been demonstrated. Tooth structure, growth and function, are considered, and related to methods of age determination. Methods are divided into those separating groups, and those for determining the chronological ages of groups. The various methods used in these two procedures are evaluated. It is pointed out that studies on the most promising method, cementum line counts, have been neglected in Africa, while methods of determining the ages of large carnivores are virtually uninvestigated, and there is a lack of basic studies describing tooth growth and changes for most large African mammals.     

Sexual dimorphism of tooth crown diameters. A contribution to the determination of the sex of subadult individuals from the early bronze age graveyard of Franzhausen I, lower Austria]

In this paper, the sexual differences between mesio-distal and bucco-lingual diameters of deciduous and permanent teeth of an Early Bronze Age population from Franzhausen are presented. Data from a total of 172 (85 male and 87 female) subadult individuals was collected. The presumptive sex determination needed for this investigation could be achieved because of specific burial rites that characterize the Unterw?lbling culture south of the Danube. The averages of both the deciduous and permanent teeth show that female individuals possess altogether teeth of smaller dimensions. The differences are, for a few permanent teeth, statistically highly significant. Using these to calculate discriminant analyses based on differing variable sets, a correct sex assignment was achieved in 81% to 75% of all cases. For the purposes of sexual diagnosis, a function combining only three measurements (MD and BL diameters of upper canine and BL diameter of the first upper molar) was 80% successful.     

Dentition and age determination of the giraffe Giraffa camelopardalis

Thirteen tooth eruption stages and their corresponding chronological ages are descri bed from a series of giraffe jaws. These can be used for age determination in giraffes with immature dentition. Significant correlations of the lingual crown height ( r =0-957; P < 0001) and lingual occlusal surface width ( r =0-959; P < 0001) with the number of dark staining incremental lines in the cementum of thin decalcified sections of the maxillary first molar were found. The regression equations derived from these relationships provide a further method for determining the age of a giraffe. A composite plate showing maxillary first molar wear patterns provides a means of roughly assigning an age to a particular specimen. Thin sections of undecalcified teeth, mandible measurements, various other indices of tooth wear and eye lens mass were investigated and found unsuitable for age determination in this     

Tooth size variation related to age in Amboseli baboons

We measured the molar size from a single population of wild baboons from Amboseli (Kenya), both females (n=57) and males (n=50). All the females were of known age; the males represented a mix of known-age individuals (n=31) and individuals with ages estimated to within 2 years (n=19). The results showed a significant reduction in the mesiodistal length of teeth in both sexes as a function of age. Overall patterns of age-related change in tooth size did not change whether we included or excluded the individuals of estimated age, but patterns of statistical significance changed as a result of changed sample sizes. Our results demonstrate that tooth length is directly related to age due to interproximal wearing caused by M2 and M3 compression loads. Dental studies in primates, including both fossil and extant species, are mostly based on specimens obtained from osteological collections of varying origins, for which the age at death of each individual in the sample is not known. Researchers should take into account the phenomenon of interproximal attrition leading to reduced tooth size when measuring tooth length for ondontometric purposes.     

Tomographic measurements of age changes in the human parotid gland

This study involved 48 subjects of both sexes with ages ranging from 22 years to 90 years. Computerised tomography was used to scan the right and left parotid gland. Gland mean density was calculated in Hounsfield units and regression graphs drawn. A significant fall in gland density was noted with subject age but no differences were noted between male and female subjects. A significant correlation was observed between the mean density of right and left glands in the same individuals. It is postulated that the fall in gland density is related an increase in fibro-fatty tissue within the gland. This study provides evidence that age related changes occur in the human parotid gland from youth to old age. This work supports the earlier findings of Scott's who studied the superficial lobe of the parotid gland histologically and found an increase in adipose tissue in this area of the gland with age.