Precise Age Estimates Research Articles

Rock‐Magnetic and Archaeointensity Investigation of Pottery and a Burned Floor at the Tzintzuntzan Archaeological Site, Western Mexico

We report a detailed rock‐magnetic and archaeointensity analysis of four pottery fragments and a burned floor recovered from the Tzintzuntzan archaeological site in western Mexico. Results from rock‐magnetic experiments (x‐T curves and first‐order reversal curves [FORC] diagrams) indicate the suitability of most of these materials as faithful geomagnetic field recorders. Potsherds were archaeomagnetically dated by comparing their mean intensity values against the paleosecular variation curve CALS3k, suggesting A.D. 600–941 as the most probable age range. This is younger than 14C‐dated charcoal from the same burned floor (A.D. 1294–1426). More precise age estimates will require the use of the full geomagnetic vector (declination, inclination, and intensity). Multiple reheatings of the ceramic pieces, evidenced as secondary components in Zijderveld plots, could reflect multiple heating of these objects, perhaps from use as incense burners. Our study demonstrates the potential of archaeomagnetic analysis to both date burned ceramics recovered in situ and provide insight into their use‐history.

Age, growth and utility of otolith morphometrics as a predictor of age in the wrasse <i>Coris julis</i> (Labridae) from the eastern Adriatic Sea

Age and growth of Coris julis were determined by examining sagittal otoliths belonging to fish sampled between November 2008 and October 2009 in the eastern Adriatic Sea (north-central Mediterranean Sea). A total of 1102 specimens (528 males, 487 females and 87 individuals of indeterminate sex), ranging from 48 to 222 mm total length were analysed. Ninety-two per cent of the otoliths were readable and 68% of the specimens had two readings in agreement. Counting of daily rings revealed that the second opaque ring represents the first annulus (315.1±27.8 daily rings). The maximum observed age was 7 years for males and 5 years for females, with males dominating in higher age classes ( > 3 years) and females in age classes 1+ and 2+. Growth was described by the von Bertalanffy growth curves and significant differences were found between males (L∞=29.10 cm, k=0.12 and t0=–1.48) and females (L∞=21.27 cm, k=0.21 and t0=–1.08). Otolith mass, length, width and thickness were determined for the otoliths belonging to 465 fish and the utility of these morphometrics as a predictor of age was evaluated. The most precise age estimations were obtained from the otolith length data, followed by the otolith mass.

Determination of Fetal Age by Ultrasonography in St. Kitts Green Monkeys

Ultrasound assessments of fetal growth have been used in other species of primates to estimate fetal age, but there are no published morphometrics for the St. Kitts green monkey (Chlorocebus sabaeus), a species that has been important for studies of transplantation of fetal tissue into the brain as potential treatment for degenerative disease. Previous studies with other primate species have used relatively small numbers of pregnancies, measured repeatedly, to derive regressions for predicting fetal age from ultrasound studies. The present study derives data from 967 pregnancies, collected over a 9-year period, for predicting fetal age from ultrasound measurements of crown rump length, biparietal diameter, head circumference, abdominal circumference, and femur length in the St. Kitts green monkey. Linear and polynomial regressions were determined from pregnancies dated from a 3- to 4-day breeding period and confirmed in a second, independent group of pregnant monkeys with more extended breeding times to determine their accuracy for predicting fetal age. Although similar to morphometrics reported in other monkey species, there were some significant differences. These data will improve the estimates of fetal ages in previously published studies of St. Kitts green monkeys and provide more precise estimates of fetal age in studies of fetal development, genomics, and reproductive toxicology.

Age of the Younger Laxá Lava and Lake Mývatn, Northern Iceland, Determined by AMS Radiocarbon Dating

Lake Mývatn and several smaller lakes in northern Iceland were formed by the large Holocene lava flow of the Younger Laxá Lava (YLL). The age of the YLL was estimated by tephrochronology at 1800–2300 BP (Thorarinsson 1951). Conventional radiocarbon dating of charred vegetation beneath the YLL (Thorarinsson 1964) yielded uncalibrated ages of 1940 ± 27014C yr BP (Yale), 2110 ± 14014C yr BP (Copenhagen), and 1990 ± 5014C yr BP (Winnipeg). Ongoing palcolimnological research at Lake Mývatn requires a more precise age estimation of the YLL. Charcoal samples from beneath the YLL were collected at Presthvammur in 2007 and analyzed by accelerator mass spectrometry (AMS)14C measurements. The reliability of the conventional14C ages of the samples Yale, Copenhagen, and Winnipeg was re-evaluated, applying criteria from Pettit et al. (2003) and Graf (2009). The result of AMS14C measurement (2170 ± 38 cal yr BP) underpins the local tephrochronology and provides a reliable age of the YLL and Lake Mývatn.

Ageing in the Danube gorges population (9500-5500 BC): Tooth cementum annulation method

Tooth cementum annulation, the microscopic method for the determination of an individual?s age, gives results that are highly correlated with the chronological age of an individual. Nevertheless, this method is still rarely used for age estimation in archaeological populations. In this study, using the tooth cementum annulation method, teeth of 21 individuals of the Djerdap anthropological series, dated to a period from the 10th to the 6th millennium BC, were analysed. The obtained data are important for overcoming some methodological issues in anthropology of the Danube Gorges, as well as with the precise age estimation of old individuals and with the assessment of age in cases where the skeletal material has been very poorly preserved. The only obstacle to the full application of the tooth cementum annulation method is the taphonomy changes of tooth cementum which were detected on several teeth in this study.

Age of the Younger Laxá Lava and Lake Mývatn, Northern Iceland, Determined by AMS Radiocarbon Dating

Lake Mývatn and several smaller lakes in northern Iceland were formed by the large Holocene lava flow of the Younger Laxá Lava (YLL). The age of the YLL was estimated by tephrochronology at 1800–2300 BP (Thorarinsson 1951). Conventional radiocarbon dating of charred vegetation beneath the YLL (Thorarinsson 1964) yielded uncalibrated ages of 1940 ± 27014C yr BP (Yale), 2110 ± 14014C yr BP (Copenhagen), and 1990 ± 5014C yr BP (Winnipeg). Ongoing palcolimnological research at Lake Mývatn requires a more precise age estimation of the YLL. Charcoal samples from beneath the YLL were collected at Presthvammur in 2007 and analyzed by accelerator mass spectrometry (AMS)14C measurements. The reliability of the conventional14C ages of the samples Yale, Copenhagen, and Winnipeg was re-evaluated, applying criteria from Pettit et al. (2003) and Graf (2009). The result of AMS14C measurement (2170 ± 38 cal yr BP) underpins the local tephrochronology and provides a reliable age of the YLL and Lake Mývatn.

Dental age assessment of southern Chinese using the United Kingdom Caucasian reference dataset

Dental age assessment is one the most accurate methods for estimating the age of an unknown person. Demirjian's dataset on a French-Canadian population has been widely tested for its applicability on various ethnic groups including southern Chinese. Following inaccurate results from these studies, investigators are now confronted with using alternate datasets for comparison. Testing the applicability of other reliable datasets which result in accurate findings might limit the need to develop population specific standards. Recently, a Reference Data Set (RDS) similar to the Demirjian was prepared in the United Kingdom (UK) and has been subsequently validated. The advantages of the UK Caucasian RDS includes versatility from including both the maxillary and mandibular dentitions, involvement of a wide age group of subjects for evaluation and the possibility of precise age estimation with the mathematical technique of meta-analysis. The aim of this study was to evaluate the applicability of the United Kingdom Caucasian RDS on southern Chinese subjects. Dental panoramic tomographs (DPT) of 266 subjects (133 males and 133 females) aged 2-21 years that were previously taken for clinical diagnostic purposes were selected and scored by a single calibrated examiner based on Demirjian's classification of tooth developmental stages (A-H). The ages corresponding to each stage of tooth developmental stage were obtained from the UK dataset. Intra-examiner reproducibility was tested and the Cohen kappa (0.88) showed that the level of agreement was 'almost perfect'. The estimated dental age was then compared with the chronological age using a paired t-test, with statistical significance set at p<0.01. The results showed that the UK dataset, underestimated the age of southern Chinese subjects by 0.24 years but the results were not statistically significant. In conclusion, the UK Caucasian RDS may not be suitable for estimating the age of southern Chinese subjects and there is a need for an ethnic specific reference dataset for southern Chinese.

Age, growth and validation of otolith morphometrics as predictors of age in the forkbeard, Phycis phycis (Gadidae)

The traditional counting of annual growth zones on thick otoliths of gadiform fish requires special processing methods and is for that reason difficult, expensive and time-consuming. Therefore, this study analysed an alternative method such as the use of otolith morphometrics as predictors of age in the forkbeard, Phycis phycis. We examined sagittal otoliths of this fish species collected from the south-eastern Adriatic Sea (Elafiti Islands) between February 2008 and February 2009. Females and males ranged in size from 19.4 to 45.8 cm and from 14.0 to 42.0 cm of the total length ( L T), respectively. Ground otoliths displayed a concentric pattern of alternating opaque and translucent zones which were used to estimate fish ages. Edge-type analysis confirmed the formation of a single growth annulus per year. The relationship between the total length and age was described by the von Bertalanffy growth model: L T = 59.08[1 − exp (−0.24( t + 0.33))] for females and L T = 75.18[1 − exp (−0.15( t + 0.70))] for males. Observed maximum age for both sexes was 5 years although most of the sampled fish were 2 years old. All measured otolith morphometric parameters (length, width and mass) were linear with fish age. The linear model explained between 61.3% and 69.0% of the variation in age. The most precise age estimations of analysed population were obtained from the otolith mass, followed by the otolith width and length. Moreover, the effectiveness of the simple otolith mass measuring technique for estimating the age of studied species was the same as of the laborious preparation and reading otoliths. It should be emphasized, however, that presented models were fitted to P. phycis ages 1–5 so extrapolation of data beyond this estimated range is not recommended.

Supervector Dimension Reduction for Efficient Speaker Age Estimation Based on the Acoustic Speech Signal

This paper presents a novel dimension reduction method which aims to improve the accuracy and the efficiency of speaker's age estimation systems based on speech signal. Two different age estimation approaches were studied and implemented; the first, age-group classification, and the second, precise age estimation using regression. These two approaches use the Gaussian mixture model (GMM) supervectors as features for a support vector machine (SVM) model. When a radial basis function (RBF) kernel is used, the accuracy is improved compared to using a linear kernel; however, the computation complexity is more sensitive to the feature dimension. Classic dimension reduction methods like principal component analysis (PCA) and linear discriminant analysis (LDA) tend to eliminate the relevant feature information and cannot always be applied without damaging the model's accuracy. In our study, a novel dimension reduction method was developed, the weighted-pairwise principal components analysis (WPPCA) based on the nuisance attribute projection (NAP) technique. This method projects the supervectors to a reduced space where the redundant within-class pairwise variability is eliminated. This method was applied and compared to the baseline system where no dimensionality reduction is done on the supervectors. The conducted experiments showed a dramatic speed-up in the SVM training testing time using reduced feature vectors. The system accuracy was improved by 5% for the classification system and by 10% for the regression system using the proposed dimension reduction method.

Precision of age estimates derived from scales and pectoral fin rays of blue sucker

Abstract Evaluating the response of fish populations to environmental influences requires precise age estimation. Pectoral fin rays and scales were compared to determine which is more precise for estimating age of blue sucker, Cycleptus elongatus (Lesueur), from the Missouri River, USA. Mean coefficient of variation was significantly lower for fin rays both among three novice readers (rays 19.9%; scales 23.1%) and among three reads by a single experienced reader (rays 11.8%; scales 18.6%). Additionally, exact per cent agreement (rays 20.0%; scales 14.3%) and within‐1‐year per cent agreement (rays 89.1%; scales 73.9%) were higher for fin rays compared with scales for multiple reads by the same experienced reader. Age–bias plots revealed that scale ages were lower than fin‐ray ages &gt;7. The use of fin rays is recommended for estimating ages of blue sucker until validation procedures are conducted.

Forensic applications of 14C at CIRCE

The decreasing trend of the radiocarbon pulse produced during the atmospheric tests of nuclear weapons (bomb-carbon) coupled with high sensitivity accelerator mass spectrometry (AMS) measurements, drastically increased the precision of radiocarbon age determinations since the second part of the sixties, allowing the application of radiocarbon AMS to a wide range of studies previously not directly involving conventional radiocarbon dating (i.e. food authenticity, forensic, biochemistry). In the framework of authenticity evaluation of artworks, high precision radiocarbon ( 14C) AMS measurements (Δ R/ R < 0.3%) reduce the conventional uncertainty of the dating to few decades, allowing precise age estimation of materials containing carbon (C). The Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) during its activity on AMS 14C dating achieved high precision measurements opening the opportunity to these kinds of applications. This paper presents the main results obtained from radiocarbon measurements on a set of bone samples analyzed for the determination of the post-mortem interval in the framework of an unsolved case investigated by the Rome prosecutor office. The chronological characterization of the wooden support of the “Acerenza portrait” is also presented with the aim to evaluate its age and to further investigate the possibility to attribute this artwork to Leonardo da Vinci. Bomb- 14C dating on the lipid and collagen fractions of bones allows the evaluation of the year of the death of the individuals by means of ad hoc calibration data sheet with the typical few years precision and difference between collagen apparent age and the year of death appeared in agreement with the age of one individual estimated by dating of tooth collagen. Conventional radiocarbon dating on both wood and wood extracted cellulose leads to an estimation of the portrait wood board age (2σ) of 1459–1524 AD (57% relative probability), 1571–1631 AD interval (42% relative probability).and 1559–1563 AD (1% relative probability). These results attribute with the highest relative probability an age comprised within the life span of Leonardo (1452–1519) to the support.

Down to Seeds and Stones: A New Look at the Subsistence Remains From Shawnee-Minisink

The Shawnee-Minisink site is well known for yielding fish and plant remains from Clovis contexts. New investigations at Shawnee-Minisink have provided a sample of macrobotanical remains for comparison with the ten plant species previously recovered at the site. In this paper, I reevaluate the subsistence remains recovered during the 1970s excavations by American University and conclude that a limited number of plants were actually exploited by the site's occupants. The new macrobotantical remains from Shawnee-Minisink have provided a series of AMS dates, which offer the most precise age estimate for Clovis in the Northeast and provide an alternative interpretation concerning the role plants played in the subsistence practices of early Paleoindians. The subsistence evidence from Shawnee-Minisink shows variation in diet, but a difference that should be expected at large habitation sites.

Age validation, and comparison of otolith, vertebra and opercular bone for estimating age of Schizothorax o’connori in the Yarlung Tsangpo River, Tibet

A collection of 514 Schizothorax o’connori was made between August 2008 and August 2009 from Yarlung Tsangpo River to assess the suitability of three bony structures for age estimation. The annulus characteristics of otolith, vertebra and opercular bone were described. Location of the first annulus was validated by daily growth increment (DGI) analysis in the otoliths. Annual periodicity was verified by marginal increment ratio (MIR) analysis in otoliths and edge analysis in vertebrae and opercular bones. Annuli formed, once a year, between March and May for all three bony structures. Otoliths, vertebrae and opercular bones were examined to determine which structure produced the most precise and accurate age estimates in S. o’connori. Vertebrae and otoliths matched closely for the first 21 years of life, while opercular bones appeared to underestimate age. For older fish, the counts diverged and otoliths consistently providing higher age estimates. Sectioned otoliths proved to be the most precise and accurate structure for age estimation. The oldest observed schizothoracine fish was 50, more than twice the longevity previously accepted in S. o’connori.

Estimating Black Crappie Age: An Assessment of Dorsal Spines and Scales as Nonlethal Alternatives to Otoliths

AbstractOtoliths generally provide more accurate and precise age estimates for crappies Pomoxis spp. than do scales, but sacrificing crappies for otolith removal may not be desirable in all situations. We evaluated the use of dorsal spines and scales as nonlethal alternatives to otoliths for estimating the ages of black crappies P. nigromaculatus using 111 fish collected from two Minnesota lakes. Among‐reader precision was similar for ages estimated from scales and dorsal spines (coefficients of variation [CVs] = 10–14%), but the precision associated with both structures was substantially lower than that observed for otoliths (CVs = 0.12–1.3%). Complete reader agreement (i.e., all three readers agreed on age) for dorsal spines (44–51%) and scales (33–36%) was substantially lower than that observed for otoliths (87–98%). Partial agreement (i.e., at least two of three readers agreed on age) was 100% for both otoliths and dorsal spines and between 79% and 89% for scales. Scale ages assigned by individual readers agreed with consensus otolith ages less than 70% of the time; agreement of individual spine ages with consensus otolith ages was 33% or less. Mean scale ages were usually similar to consensus otolith ages for crappies between the ages of 2 and 6 years, while mean spine ages were consistently lower than consensus otolith ages. Thin‐sectioning dorsal spines did not significantly change the number of annuli detected by individual readers. Our results suggest that dorsal spines are not a useful alternative to scales for estimating black crappie age in a nonlethal manner. A conspicuous lumen located in the center of each dorsal spine partially or fully obscures at least one annulus. When otolith removal is not desirable, use of scales and multiple readers may provide mean age estimates that are similar to consensus otolith ages, but we suggest that otolith analysis remains the most reliable method for estimating black crappie age, regardless of latitude.

A rapid method for hand picking potassium-rich feldspar from silicic tephra

We detail a method for hand picking potassium-rich feldspars from silicic tephra. The method, based on the well known sodium cobaltinitrite staining technique, is applicable to any sample where K content of feldspar exceeds ∼2 wt%. The method is well suited to mineral grains >0.25 mm and useful for grains as small as ∼0.125 mm. Alkali feldspar, plagioclase, and quartz are easily distinguishable after staining. Rinsing the stained feldspars along with ultrasonic treatment in distilled water and nitric acid removes the stain. 40Ar/ 39Ar analysis of sanidine separated by staining yields precise age estimates which are in excellent agreement with published ages for the youngest (2.06 Ma) Cerro Galán ignimbrite, NW Argentina.

An OSL chronology for the sedimentary deposits from Pinnacle Point Cave 13B—A punctuated presence

Optically stimulated luminescence (OSL) measurements are reported for single aliquots and single grains of quartz from sedimentary deposits within Cave 13B at Pinnacle Point, South Africa (PP13B). Ages have been obtained for 30 samples from the Middle Stone Age and from sterile geological deposits at the base and top of the sediment sequence. The ages for all the archaeological units have been obtained from single-grain measurements that enable unrepresentative grains to be rejected after they have been scrutinized for their OSL behavior. The shape of the equivalent dose distribution and the degree of spread in equivalent dose for each sample have also been scrutinized for evidence of depositional and post-depositional effects that can influence the accuracy of the age estimates. This study also used the same systematic approach as that used for the dating of the Howieson’s Poort and Still Bay in South Africa. This single-grain approach results in more accurate and precise age estimates that place all ages measured and analyzed in this way on a common timescale. Four periods of human occupation have been dated to ∼162 ka, ∼125 ka, ∼110 ka, and ∼99–91 ka during Marine Isotope Stage (MIS) 6, 5e, 5d, and 5c, respectively. Occupation of the site appears to have occurred at periods of higher sea level and increased aeolian activity, and the cave was ultimately sealed by the accumulation of a large dune ∼90 ka ago that infilled the cave, but also blanketed the cliff face above the cave, thus preventing further habitation of the site until ∼39 ka.

Estimation of individual age and season of death in woolly rhinoceros, Coelodonta antiquitatis (Blumenbach, 1799), from Sakha-Yakutia, Russia

A unique find of a woolly rhinoceros skull bearing both nasal and frontal horns is described from a thermokarst lake of the Bol’shaya Chukoch’ya River basin in north-eastern Republic of Sakha (Yakutia), Russia. Based on counts of cementum layers of the maxillary first molar and dark and transverse bands of the nasal and frontal horns a correlation of individual age records within these structures is established. Both estimations of individual age are agreed as well as three other age estimation criteria followed from cranial characteristics, general aspects of dentition and tooth wear pattern. Thus, the number of horn bands, which is equal to 30 or 31, does express the individual age at the moment when the woolly rhinoceros died. The tooth cementum and both horns are proved to be recording structures of woolly rhinoceroses which can be used as precise individual age estimation criteria. The season in which death occurred is also discussed.

Age estimation obtained from analysis of octopus ( Octopus vulgaris Cuvier, 1797) beaks: Improvements and comparisons

Two methods are currently available for age estimation in octopus beaks. They have been applied to the same specimen from a sample of 30 individuals of Octopus vulgaris caught in central-eastern Atlantic waters. These techniques aim at revealing growth increments in the rostrum sagittal sections (RSS) and lateral wall surfaces (LWS) of octopus upper and lower beaks. Both methods were improved to reduce the time of sample preparation and to enhance the appearance of the increments. For each individual, two independent readings were done for upper and lower beak sections, as well as for the lateral wall surfaces. Vertical reflected light (epifluorescence) and image analysis system were shown to be useful in the observation and analysis of the sequence of increments. Precision of the ageing, increment counts obtained by both techniques, and increment widths were discussed. Using upper beak RSS led to more precise age estimates, whereas preparing LWS was quicker and simpler, and revealed a higher number of increments. Therefore, our study recommends counting growth increments in LWS of beaks to age adult common octopus.

Calibrating the Cryogenian

The Neoproterozoic was an era of great environmental and biological change, but a paucity of direct and precise age constraints on strata from this time has prevented the complete integration of these records. We present four high-precision U-Pb ages for Neoproterozoic rocks in northwestern Canada that constrain large perturbations in the carbon cycle, a major diversification and depletion in the microfossil record, and the onset of the Sturtian glaciation. A volcanic tuff interbedded with Sturtian glacial deposits, dated at 716.5 million years ago, is synchronous with the age of the Franklin large igneous province and paleomagnetic poles that pin Laurentia to an equatorial position. Ice was therefore grounded below sea level at very low paleolatitudes, which implies that the Sturtian glaciation was global in extent.

Comparison of Scales and Sagittal Otoliths to Back-Calculate Lengths-at-Age of Crappies Collected from Midwestern Waters

ABSTRACT Back-calculation is commonly used in age and growth studies to increase the sample size when few fish are captured from a population; however, which structure to use for back-calculation has been often disputed. We compared back-calculated lengths of crappie (Pomoxis spp.) scales and sagittal otoliths from seven Midwestern lakes using linear regression. To examine this relationship on a finer scale, a residual sum of squares (RSS) analysis was also run to determine whether the two structures suggested different mean lengths at age for one population (Cedar Lake, Illinois). A total of 150 fish, age-1 to age-10 (mean 2.8 years), was collected from all lakes; a total of 296 back-calculated lengths was obtained for each structure. Thirteen fish were discarded because of lack of age agreement between structures. Overall for all lakes, the otolith versus scale back-calculated lengths regression yielded an intercept of-22.19 mm and a slope of 1.00 (R2=0.77, df=1, 296, P<0.0001). The slope was not different from 1.00 (95% CI of 0.94–1.07), but the intercept was slightly different from zero (95% CI of-34.66 to −9.72). Furthermore, the RSS analysis suggested that the growth curves for Cedar Lake did not differ between structures (F3,2=0.29, p>0.75), indicating that the pattern seen across all lakes held true for one population. Either structure could be used for back-calculation studies. However, perfect agreement of ages between structures (i.e., scales and otoliths) did not occur. Crappie length at age should be back-calculated using otoliths when more precise age estimates are needed and with scales when fish are too few to be killed.