Paper short abstract:

To clarify human population structure in the Ryukyu Islands, genome-wide SNP typing was performed for the Ryukyu Islanders. The results indicated genetic divergence between the people of the Okinawa Islands and the Miyako Islands. We estimated the divergence time between the subpopulations within the Holocene.

Paper long abstract:

The Ryukyu Islands are located in southwestern part of the Japanese archipelago and consist of the Amami Islands, Okinawa Islands, Miyako Islands, and Yaeyama Islands and the other islands. Archaeological evidence has indicated the prehistoric cultural differentiation between the northern Ryukyu—the Amami Islands and the Okinawa Islands― and the southern Ryukyu—the Miyako Islands and Yaeyama Islands. These geographical and archaeological backgrounds imply a population subdivision between these sub-regions. To clarify detailed population structure in the Ryukyu Islands, we performed genome-wide SNP typing for the people of the Okinawa Islands, the Miyako Islands, and the Yaeyama Islands. Principal component analysis and clustering analysis using SNP data suggested a genetic differentiation between people of the Okinawa and the Miyako Islands, as well as migration from the Okinawa Islands to the Yaeyama Islands. No genetic affinity was observed between aboriginal Taiwanese and any Ryukyu populations. Therefore, the genetic differentiation between people of the Okinawa and the Miyako Islands is likely to have been caused by genetic drift rather than admixture with the aboriginal Taiwanese. Based on the genetic differentiation, we estimated the divergence time between people of the Okinawa and the Miyako Islands within the Holocene. These findings suggest that the Pleistocene people, whose bones have been excavated in the southern Ryukyu, did not have major genetic contribution, if any, to the present-day southern Ryukyu Islanders.

Paper short abstract:

The aim of this presentation is to examine the number of missing teeth in ancient Japanese. Ancient Japanese people had many remaining teeth. This result was unexpected. The notion that “ancient peoples lost more teeth more quickly” does not seem to apply to ancient skeletal remains from Japan.

Paper long abstract:

Excavated human skeletal remains consists of Kofun (4th-7th), Kamakura (1185-1333 AD), Muromachi (1336-1573 AD) and Edo (1603-1868 AD) periods have shown that Japanese people maintained a surprisingly high number of remaining teeth even in pre-modern times. The materials were 145 excavated human skeletons whose maxillas and mandibles were both examinable. The individuals were divided into groups, such as the early middle age and the late middle age. The status of missing teeth was compared between groups. The rates of tooth loss were examined in the maxillas and the mandibles. In people of every period, many teeth remained in good condition until early to late middle age. However, people of all periods clearly showed increased tooth loss with age. Dental caries and periodontal disease were two major diseases in pre-modern Japan. However, the average life span remained almost unchanged from the Kofun period approximately more than 1500 years ago until the pre-modern times in the Edo period. This lack of improvement was speculated to be due to insufficient intake of nutrition from food and deaths from infection. The number remaining of teeth was low in the elderly individuals, and a large number of lost teeth were likely directly associated with death in periods before modern times. In modern oral medicine, the focus has been on how to reduce eating impairments. The reason is that body functions rapidly decline when nutrient intake is insufficient, which can directly lead to death in elderly individuals.

Paper short abstract:

The incidence of caries and periodontitis were compared on the Jomon skeletal remains from two sites, Nakazuma shell-midden and mountainous inland Kitamura sites. Results suggest a different level of carbohydrate consumption and a plausible sexual division of dietary subsistence behavior.

Paper long abstract:

As for the prevalence of caries and periodontitis in Jomon people in Japan, previous studies have reported a relatively higher caries incidence (ca. 10% on average) compared to an average of prehistoric hunter-gatherers, and have estimated a widely prevailing affection of periodontal diseases for the Jomon population. However, we have now realized a wide variation in the caries incidence among sites of Jomon and a lack of tangible data of periodontitis for them. We present and compare here the prevalence of caries and periodontitis for two Jomon sites, Nakazuma shell-midden and mountainous inland Kitamura sites, where different environmental resources possibly affect a variety of subsistence patterns on diet. Results indicate that both caries and periodontitis are prevalent and the sex differences are significant in Nakazuma, while Kitamura site possesses low caries and high periodontitis rates with negligible sex differences. Although the caries and the periodontitis are both infectious via intraoral bacteria, the former is more linked to carbohydrate consumption in the diet. The results suggest that Nakazuma Jomon people might have a more carbohydrate diet than the Kitamura, and that the former society might form a level of sexual division in dietary collection, distribution and consumption behavior leading to the significant sex difference in the prevalence of caries and periodontitis.

Paper short abstract:

To date, several anthropologists have estimated the life expectancy of Jomon people. However, those estimations are all skeptical due to possible sampling biases and the erroneous age estimations of the skeletal remains. I estimated the life expectancy by using their teeth and the Bayesian approach, to circumvent those problems.

Paper long abstract:

According to several reports of demographic survey on the modern hunter-gatherer populations, their life expectancies at age 15 range between 32 and 55 years. Contrarily, the life expectancy of Jomon people was once estimated as about 16 years, based on estimated ages of the skeletal remains. There are, at least, two errors that may have caused the estimation for Jomon life expectancy to be too short. One is the sampling bias preferring young skeletons to old ones. The other is the biased age estimation caused by the age distribution of reference samples dominated by young skeletons. Sampling tends to prefer young-adult skeletons because young adults have more durable skeleton and, after the death, more likely preserve their skeletal parts for the age estimation than old ones. The reduction of bone-remodeling activity in the old age is presumably the cause for the differential preservation. To circumvent this problem, I used the tooth as the age indicator; the dental pulp volumes were measured and the shrinkages were regarded as showing the progress of age. Unlike in bones, remodeling process does not occur in teeth; thus, the sampling bias caused by differential preservation was expected to be minimized. To circumvent the second problem (the biased age estimation), I employed Bayesian approach; this approach can avoid influence of the age distribution of reference samples. Bayesian approach was employed once before to estimate Jomon life expectancy, but the manner of application was inappropriate. I used and suggest in this paper an appropriate application of Bayesian approach. The result showed that life expectancy of Jomon people at age 15 should have been in between 29 and 42 years, the lower range of the modern hunter-gatherer populations.

Paper short abstract:

We estimated the cerebellar-cerebrum volume ratio of Middle Paleolithic modern humans and Neanderthals. The former is comparable to the present-day humans, while the Neanderthals have had relatively small cerebella. Co-authors: Tanabe H, Ogihara N, Yogi A, Murayama S and Ishida H.

Paper long abstract:

Neanderthals are an extinct human species who had large brains comparable to modern humans. To what extent Neanderthal cognitive abilities were similar to those of modern humans is currently under intensive debate. We compared the cerebro-cerebellar volume ratio as a plausible way to infer the difference in cognitive ability among the Neanderthals, Middle Paleolithic modern humans, and present-day humans.

First, we devised a new method to estimate the cerebral and cerebellar volumes, which was derived from the volumetric relationships between endocranial subregions (i.e. supratentorial and posterior cranial fossa regions) and brain components (i.e. cerebrum and cerebellum) based on MRI data of living human subjects (n=32). To validate the accuracy of MRI measurements, the volumes of endocranial portions were calibrated by coefficient factors derived from paired comparison between the CT and MRI measurements of the same individuals (n=3). We found that the volumes of endocranial subregions are useful estimators for the cerebral/cerebellar volumes.

We then applied our estimation method to the Neanderthal (n=3) and the Middle Paleolithic modern humans from Levant (n=2). The results were partly consistent with previous reports that the Neanderthals have relatively smaller cerebella compared to the living human sample. On the other hand, we also found that the earlier Levantine specimens are comparable to the living human sample in their relative cerebellar volumes. These results indicate that the Middle Paleolithic modern humans already have had cognitive functions comparable to present-day humans while the Neanderthals have not.

Paper short abstract:

We provide an overview of the early Acheulean assemblages from Konso, Ethiopia. The Konso evidence suggests emergence of the Acheulean before ~1.75 Ma, gradual refinement to ~1.0 Ma, and a significant technological advance resulting in well-trimmed and thin handaxes by ~0.85 Ma. Co-authors: Yonas Beyene (A.R.C.C. Awassa, Ethiopia), and Berhane Asfaw (Rift Valley Research Service, Ethiopia).

Paper long abstract:

Acheulean tools are known from large stone tools called "handaxes", "cleavers", and "picks", and are often considered the first tools to be purposely shaped into preconceived form. Many think that handaxes were used in butchering and skinning animal carcasses, and, in some instances, represent advanced cognition and symbolic behavior. The Acheulean has been considered a long-lasting monotonic lithic tradition that spanned ~1.5 Ma to ~0.3 Ma or younger, from Africa to southern Asia, indicating remarkable behavioral conservatism through time and space. Here, based on evidence from Konso, Ethiopia, spanning ~1.75 Ma to 0.85 Ma, we provide a somewhat different perspective of the Acheulean. The Konso evidence indicates that both heavy-duty picks and handaxes were important components throughout the early Acheulean, probably representing different functions. The handaxes become better shaped through time, implying gradual refinement of both shape and function, but they remain thick with sinuous edges until at least ~1.0 Ma. However, by ~0.85 Ma, well-trimmed and thin handaxes started to be made, suggesting a significant advance in tool function, workmanship, and perhaps cognition. Thus, there appears to have been two important periods of innovation represented in the Acheulean sequence, one at ~1.75 Ma when both Acheulean tools and Homo erectus were emerging, and another at 1.0 Ma to ~0.8 Ma, preceding or broadly paralleling the transition of Homo erectus to a more advanced species of Homo.