Usefulness of powdered crown of mandibular first premolars in birth year estimation by radiocarbon dating.

BACKGROUND: Radiocarbon (14C), whose levels increased in the atmosphere between 1955 and 1963, accumulates in the enamel of human teeth only during the process of tooth formation and has been applied to estimate the birth year of unidentified corpses. However, enamel isolation from teeth is time-consuming and labor-intensive. Therefore, this study aimed to estimate the birth year using 14C in the crown of a single mandibular first premolar tooth. MATERIALS AND METHODS: Fourteen mandibular first premolars collected from forensic autopsies were analyzed. For nine teeth, each tooth was cut longitudinally: half of the tooth was enamel, and the other half was crown (1). For the other five teeth, the entire crown was used (2). Thereafter, the 14C concentration in each tooth was measured using accelerator mass spectrometry. RESULTS: The absolute error between the actual date of birth (DOB) and the estimated DOB was within the range of 1.0-8.8 years in the enamel of five teeth and 0.1-4.0 years in the crown halves of seven teeth (1). For the five teeth with entire crowns, the absolute errors ranged between 0.3 and 3.0 years (2). CONCLUSION: The absolute error of 14C-based year of birth estimation using the powdered crown of the mandibular first premolar teeth ranged between 0.1 and 4.0 years. Our method, which involves pulverizing an entire crown, eliminates the need for the equipment, time, and labor associated with enamel isolation. Therefore, 14C dating using powdered crowns of mandibular premolars can be useful for birth year estimation.

Bioarchaeological study of ancient Teotihuacans based on complete mitochondrial genome sequences and diet isotopes.

BACKGROUND: The Teotihuacan civilisation was the largest one in ancient Mesoamerica. The Teotihuacan city was born in the north-eastern Basin of Mexico around the second century BC, reached its peak in the fourth century AD, and had cultural influence throughout Mesoamerica. At its peak, the size of the city reached more than 20 km2, and the total population is estimated to have increased from 100,000 to 200,000. However, knowledge of the genetic background of the Teotihuacan people is still limited. AIM: We aimed to determine the mitogenome sequences of the Teotihuacan human remains and compare the ancient and present Mesoamericans. In addition, we aimed to identify the food habits of ancient Teotihuacans. SUBJECTS AND METHODS: We determined the mitogenome sequences of human remains dated to 250-636 cal AD using target enrichment-coupled next generation sequencing. We also performed stable isotope analysis. RESULTS: We successfully obtained nearly full-length sequences newly unearthed from a civilian dwelling in the Teotihuacan site. Teotihuacan mitochondrial DNA was classified into the haplogroups in present and ancient Mesoamericans. In addition, Teotihuacan individuals had a diet dependent on C4 plants such as maize. CONCLUSION: Genetic diversity varied among the Teotihuacans.

Paleogenomics reveals independent and hybrid origins of two morphologically distinct wolf lineages endemic to Japan.

Little is known about the spatiotemporal dynamics of gray wolves in the Pleistocene across low-latitude regions of Eurasia. In Japan, a small-bodied endemic subspecies of Japanese wolves existed and went extinct in the early 1900s. The fossil record indicates that a giant wolf, which reached 70 cm in body height, inhabited Japan during the Pleistocene, but its evolutionary relationship, if any, with the Japanese wolf remains uncertain. Here, to reveal the genetic origin of the Japanese wolf, we analyzed ancient DNA from remains (recovered in Japan) of one Pleistocene wolf that lived 35,000 years ago and one Holocene wolf from 5,000 years ago. The analysis of the mitochondrial DNA revealed that the Pleistocene wolf was not part of the Japanese wolf clade but rather an earlier-diverging lineage. The analysis of the nuclear DNA of the Holocene Japanese wolf revealed that it was an admixture of the Japanese Pleistocene wolf and continental wolf lineages. These findings suggest that the Japanese wolf originated via waves of colonization of multiple Pleistocene wolf populations at 57-35 and 37-14 ka, respectively, followed by interpopulation hybridization.

Ancient DNA reveals multiple origins and migration waves of extinct Japanese brown bear lineages.

Little is known about how mammalian biogeography on islands was affected by sea-level fluctuations. In the Japanese Archipelago, brown bears (Ursus arctos) currently inhabit only Hokkaido, the northern island, but Pleistocene fossils indicate a past distribution throughout Honshu, Japan's largest island. However, the difficulty of recovering ancient DNA from fossils in temperate East Asia has limited our understanding of their evolutionary history. Here, we analysed mitochondrial DNA from a 32 500-year-old brown bear fossil from Honshu. Our results show that this individual belonged to a previously unknown lineage that split approximately 160 Ka from its sister lineage, the southern Hokkaido clade. This divergence time and fossil record suggest that brown bears migrated from the Eurasian continent to Honshu at least twice; the first population was an early-diverging lineage (greater than 340 Ka), and the second migrated via Hokkaido after approximately 160 Ka, during the ice age. Thus, glacial-age sea-level falls might have facilitated migrations of large mammals more frequently than previously thought, which may have had a substantial impact on ecosystem dynamics in these isolated islands.

Gradual onset of the Maunder Minimum revealed by high-precision carbon-14 analyses.

The Sun exhibits centennial-scale activity variations and sometimes encounters grand solar minimum when solar activity becomes extremely weak and sunspots disappear for several decades. Such an extreme weakening of solar activity could cause severe climate, causing massive reductions in crop yields in some regions. During the past decade, the Sun's activity has tended to decline, raising concerns that the Sun might be heading for the next grand minimum. However, we still have an underdeveloped understanding of solar dynamo mechanisms and hence precise prediction of near-future solar activity is not attained. Here we show that the 11-year solar cycles were significantly lengthened before the onset of the Maunder Minimum (1645-1715 CE) based on unprecedentedly high-precision data of carbon-14 content in tree rings. It implies that flow speed in the convection zone is an essential parameter to determine long-term solar activity variations. We find that a 16 year-long cycle had occurred three solar cycles before the onset of prolonged sunspot disappearance, suggesting a longer-than-expected preparatory period for the grand minimum. As the Sun has shown a tendency of cycle lengthening since Solar Cycle 23 (1996-2008 CE), the behavior of Solar Cycle 25 can be critically important to the later solar activity.

A biomolecular anthropological investigation of William Adams, the first SAMURAI from England.

William Adams (Miura Anjin) was an English navigator who sailed with a Dutch trading fleet to the far East and landed in Japan in 1600. He became a vassal under the Shogun, Tokugawa Ieyasu, was bestowed with a title, lands and swords, and became the first SAMURAI from England. "Miura" comes from the name of the territory given to him and "Anjin" means "pilot". He lived out the rest of his life in Japan and died in Hirado, Nagasaki Prefecture, in 1620, where he was reportedly laid to rest. Shortly after his death, graveyards designated for foreigners were destroyed during a period of Christian repression, but Miura Anjin's bones were supposedly taken, protected, and reburied. Archaeological investigations in 1931 uncovered human skeletal remains and it was proposed that they were those of Miura Anjin. However, this could not be confirmed from the evidence at the time and the remains were reburied. In 2017, excavations found skeletal remains matching the description of those reinterred in 1931. We analyzed these remains from various aspects, including genetic background, dietary habits, and burial style, utilizing modern scientific techniques to investigate whether they do indeed belong to the first English SAMURAI.

Prolonged production of 14C during the ~660 BCE solar proton event from Japanese tree rings.

Annual rings record the intensity of cosmic rays (CRs) that had entered into the Earth's atmosphere. Several rapid 14C increases in the past, such as the 775 CE and 994CE 14C spikes, have been reported to originate from extreme solar proton events (SPEs). Another rapid 14C increase, also known as the ca. 660 BCE event in German oak tree rings as well as increases of 10Be and 36Cl in ice cores, was presumed similar to the 775 CE event; however, as the 14C increase of approximately 10‰ in 660 BCE had taken a rather longer rise time of 3-4 years as compared to that of the 775 CE event, the occurrence could not be simply associated to an extreme SPE. In this study, to elucidate the rapid increase in 14C concentrations in tree rings around 660 BCE, we have precisely measured the 14C concentrations of earlywoods and latewoods inside the annual rings of Japanese cedar for the period 669-633 BCE. Based on the feature of 14C production rate calculated from the fine measured profile of the 14C concentrations, we found that the 14C rapid increase occurred within 665-663.5 BCE, and that duration of 14C production describing the event is distributed from one month to 41 months. The possibility of occurrence of consecutive SPEs over up to three years is offered.

Estimation of birth year by radiocarbon dating of tooth enamel: Approach to obtaining enamel powder.

Atmospheric radiocarbon (14C) levels increased from 1955 to 1963 due to atmospheric nuclear weapon tests, and then decreased. As 14C accumulates in human tooth enamel while the enamel is being formed, 14C can be used to estimate the birth year of unidentified bodies. Measurement results of 14C content in tooth enamel using accelerator mass spectrometry vary depending on the enamel's sample site. To address this problem, a method for equalizing samples using a pulverizer was considered in this study. Regarding the tube and cone used as the pulverizer, (1) a polycarbonate tube and stainless steel cone, (2) a stainless steel tube and cone, and (3) a tungsten carbide tube and cone, were compared. In (1), the modern carbon ratio was approximately half that of the normal ratio of 100 pMC, with which accurate dating was impossible, and in (2), a high background value was obtained for IAEA-C1, which was pulverized using a reusable tube and cone. In (3), the 14C content for IAEA-C1 pulverized using reusable tube and cone, which was washed with quartz sand, was 0.31 ±â€¯0.01 pMC. This result did not show any problems regarding background value. Therefore, the use of tungsten carbide products and washing with quartz sand is recommended for 14C measurement of pulverized teeth.

Temporal variation of (7)Be concentrations in atmosphere for 8y from 2000 at Yamagata, Japan: solar influence on the (7)Be time series.

We have been continuously observing the daily (7)Be concentrations in surface air at Yamagata, Japan (38.25 degrees N, 140.35 degrees E) since 2000. The yearly profile of the (7)Be concentration indicates the variation in galactic cosmic rays owing to solar modulation. Over 8y, the (7)Be concentration, cosmic neutrons, and number of sunspots varied by 37.4%, 12.2%, and 92.8%, respectively. The influence of precipitation on the (7)Be variability was approximately 5%. Hence, the yearly (7)Be concentration was mainly varied by the solar modulation of the (7)Be production rates. Based on the production rates found in an EXPACS simulation, the observed variability indicates (7)Be transport from high latitudes. The daily (7)Be concentrations have two significant periodic components of 19d and 36d. The 36-d component implies a relationship between the sun's rotation and the vertical transport of air masses under quiet solar activity.