Infant feeding practice in medieval Japan: stable carbon and nitrogen isotope analysis of human skeletons from Yuigahama-minami.

A longer breastfeeding duration provides various positive effects in subadult health because of abundant immunological factors and nutrients in human breast milk, and decreases the natural fertility of a population through lactational amenorrhea. In this study, we measured stable carbon and nitrogen isotope ratios in the bone collagen of three adults and 45 subadults from the Yuigahama-minami site (from 12th to 14th century) in Kamakura, the early medieval capital of Japan. Marine foods, C3 -based terrestrial foods, and freshwater fish are the primarily protein sources for adults. The changes in the nitrogen isotope ratios of subadults suggest that the relative dietary protein contribution from breast milk started to decrease from 1.1 years of age and ended at 3.8 years. The age at the end of weaning in the Yuigahama-minami population was greater than that in the typical non-industrial populations, a premodern population in the Edo period Japan, and medieval populations in the UK. Skeletons of townspeople from medieval Kamakura indicate severe nutritional stress (e.g., enamel hypoplasia and cribra orbitalia), yet this longer duration of breastfeeding did not compensate adverse effects for nutritional deficiency. The longer breastfeeding period may have been a consequence of complementary food shortage and bad health of subadults. Kamakura experienced urbanization and population increase in the early medieval period. The younger age-at-death distribution and high nutritional stresses in the Yuigahama-minami population and later weaning, which is closely associated with longer inter-birth interval for mothers, suggests that Kamakura developed and increased its population by immigration during urbanization.

Stable isotopic reconstructions of adult diets and infant feeding practices during urbanization of the city of Edo in 17th century Japan.

The urbanization of the city of Edo, the capital of premodern Japan, has been assumed to be not as a result of natural increase but that of in-migration although this assumption has never been verified. To obtain information on natural fertility in Edo, we analyzed stable carbon and nitrogen isotopes in 46 adult and 84 subadult human skeletons excavated from the Hitotsubashi site (1657-1683 AD: the early Edo period), Tokyo, Japan and reconstructed their breastfeeding period, one of the most important determinants of fertility. Adult females are significantly more depleted in (15) N by 0.7‰ than adult males, suggesting a dietary differentiation between sexes and/or the effect of pregnancy. The changes in the nitrogen isotope ratios of subadults suggest that supplementary foods were introduced around the age of 0.2 years and weaning ended around 3.1 years, which agrees with descriptions in various historical documents of the period. The duration of breastfeeding in the Hitotsubashi population was relatively longer than those in modern industrial and traditional societies and four previously reported populations in medieval and in the industrial England. As later weaning closely associates with longer inter-birth interval for mothers, our data suggest a lower natural fertility for the Hitotsubashi population. Assuming that the proportion of married people was also lower in the major cities of the earlier Edo period, our results support the assumption that Edo developed and increased its population by attracting immigrants during urbanization.

Mitochondrial DNA analysis of Hokkaido Jomon skeletons: remnants of archaic maternal lineages at the southwestern edge of former Beringia.

To clarify the colonizing process of East/Northeast Asia as well as the peopling of the Americas, identifying the genetic characteristics of Paleolithic Siberians is indispensable. However, no genetic information on the Paleolithic Siberians has hitherto been reported. In the present study, we analyzed ancient DNA recovered from Jomon skeletons excavated from the northernmost island of Japan, Hokkaido, which was connected with southern Siberia in the Paleolithic period. Both the control and coding regions of their mitochondrial DNA (mtDNA) were analyzed in detail, and we confidently assigned 54 mtDNAs to relevant haplogroups. Haplogroups N9b, D4h2, G1b, and M7a were observed in these individuals, with N9b being the predominant one. The fact that all these haplogroups, except M7a, were observed with relatively high frequencies in the southeastern Siberians, but were absent in southeastern Asian populations, implies that most of the Hokkaido Jomon people were direct descendants of Paleolithic Siberians. The coalescence time of N9b (ca. 22,000 years) was before or during the last glacial maximum, implying that the initial trigger for the Jomon migration in Hokkaido was increased glaciations during this period. Interestingly, Hokkaido Jomons lack specific haplogroups that are prevailing in present-day native Siberians, implying that diffusion of these haplogroups in Siberia might have been after the beginning of the Jomon era, about 15,000 years before present.

Tubular anomalous bones found in both thighs of a long-tailed macaque (Macaca fascicularis).

Tubular anomalous bones were found in both thighs of a 6-year-old male long-tailed macaque (Macaca fascicularis) bred in captivity. The bones had jagged ends and protruded from the skin. Radiographs showed that they developed in the femurs at the middle and elongated. They were removed with surgery under anesthesia. Histological analysis revealed that these bones had the same histological structure as the femur, though they were composed of primary and secondary osteon regions. This finding indicated that the new bones developed from the old bone piece(s), acquired a tubular shape, and elongated. It is suggested that the anomalous bones were produced not by the congenital deformity but by regeneration from fragments of the fractured femur that were embedded in the bone marrow; these acquired a tubular pattern and elongated.