Persistent problems involving the clavicle include the reason for its reduction in many mammals, its function in hominids, the last ossification, and so on. In this paper these problems are considered from the point of views of comparative and functional morphology. The clavicle is an element of the dermal shoulder girdle that is in the process of reduction through tetrapod evolution. The reason why the clavicle disappeared or was reduced in cursorial mammals is probably that it disturbed the reciprocal movement of the scapula. The human clavicle works also as a supporter of the forelimb. The characteristic double-curved form of the clavicle may be related to its function. The sternal epiphysis of the clavicle fuses last among the long bones of the human skeleton, in spite of the first ossification of the clavicular body. The delay of determination of the clavicular length should be convenient to slight adjustment for retaining dynamic stability in human bipedal walking.
Basic statistics on cranial measurements from 15 modern Japanese populations were compiled by the Commission of Anthropological Investigation of Modern Japanese Crania. These data were analyzed in order to evaluate the magnitude of inter-population differences and the influence of secular change on the interpopulation differences. Cranial measurements taken for four populations from the late Edo period were used to estimate the inter-population differences that can be caused by systematic inter-observer measurement errors and by the bias in the sampling. The distance measures based on the measurement items with small intraand inter-observer measurement errors indicate that the inter-population differences in modern Japanese crania are much greater than the differences caused by the measurement error. However, the differences caused by sample bias are as large as some of the inter-population differences. The results of cluster analyses indicate that the influence of secular change can not be ignored. According to the results of discriminant analysis, the key characteristic in determining inter-population difference is maximum cranial breadth. Since secular change is observed in seven out of 13 measurement items with significant inter-population differences, a considerable part of so-called geographic differences among modern Japanese crania is likely to be due to the secular change that took place during the 100 year period required to collect the materials.
Incidences of 22 nonmetric cranial traits were compared through uni-and multi-variate procedures between seven cranial series from the central islands of Japan covering the past 4, 000 years of Japanese population history. The results indicated that there is a clear difference in the incidence of nonmetric traits between the native Jomon and the immigrant Yayoi, but thereafter, the incidence has remained stable over the 2, 000 years from the Yayoi period to the present time. Taken these together, it is inferred that the northern Kyushu Yayoi of continental lineage must be one of the lineal forerunners of the modern Japanese of the central islands of Japan.
The emergence ages of third molars in a modern Japanese population were examined, and the results were compared with those for other ethnic groups. The subjects of the study consisted of 983 individuals (539 males and 444 females) aged 18 to 40 years. The family backgrounds of all of the individuals studied were presumed to be of the middle-class socioeconomic group. In each case, a third molar was judged to have erupted if any part of the tooth crown had pierced the gingiva. The median emergence age was estimated by probit analysis of the incidence of eruption, measured as the number of persons at each age level with one or more third molars erupted. The median emergence age was 19.59 years for males and 20.67 years for females. More third molars had erupted in males than in females at any given age. Also, mandibular molars tended to have erupted earlier than their maxillary counterparts, especially in females. Viewed from a global perspective, the Japanese population was characterized as experiencing third molar emergence at a relatively late age.
Longitudinal growth of height, chest girth and weight was examined in 358 boys and 400 girls born during 1961-1969 and raised in Tokyo. The data consist of two series: Data K (234 boys and 252 girls) assembled by the present authors and Data T (124 boys and 148 girls) by TAKEI (1980). The age at peak velocity (PV age) was calculated for each item of measurement by the individual, and their interrelation of the items was examined. In girls, the menarchial age was also referred to. (1) In average, adolescent spurt occurred first in height, followed by chest girth, and finally weight. Menarche occurred in average at 1.3 years later than the PV age of height (Table 1). (2) The Correlation coefficient of the PV ages was the largest (greater than 0.7) between height and weight, next between weight and chest girth, and smallest between height and chest girth. As for the menarchial age, the PV age of height correlated highly, weight the next, and chest girth correlated the lowest (Table 2). (3) For a detailed analysis of the individual growth pattern, personal time intervals between the PV ages of the three items were calculated to obtain incidence according to 1 year divisions (Tables 3-5). In about 70% of the examinees of both sexes, the chest girth-growth spurt occurred within + 1 year of the height-growth spurt: the examinees passed through adolescence without marked fluctuation of their body type. The incidence of weight-growth spurt occurring one or more years later than height-growth spurt was found to be three times greater in the girls than in the boys. The chest girth-growth spurt occurred closely before and after the weight spurt in a large number of boys and girls. (4) In the majority of the girls, menarche occurred behind the growth spurt of all three items of measurement (Tables 6 and 7). (5) It was an average trend that, in boys, adolescent growth of height and weight first accelerated in step, then was followed by that of girth, while in girls adolescent growth of height first accelerated, then was followed by weight and girth in step. However, the non-abnormal appearance of a few exceptions to the average trend must be taken into consideration in the analysis of the individual patterns of adolescent growth (Tables 4 and 5).
A full description of seven human skeletal remains of the early middle Yayoi period, excavated in 1980 and 1982 at the Iwatsubo cave site, Manba-cho, Tano-gun, Gunma Prefecture, Japan is given. These are the first well-preserved human skeletal remains of the Yayoi period from an inland site in the Kanto district. Comparative analyses with east Japan Jomon, east Japan Kofun, northern Kyushu Yayoi and recent Kanto populations were made. The inventory and osteological measurements of the Iwatsubo remains are shown in Tables 1 to 8. Recent morphological and genetical studies have resulted in a consensus view that the recent Japanese are genetically greatly influenced by immigrants from the Asian Continent since the Yayoi period. Whether the people of the Iwatsubo site retained skeletal features characteristic of Jomon populations or possessed those of the immigrants is the major focus of this paper. Two of the Iwatsubo specimens (both are adult female) are relatively complete and showed considerable morphological similarities with the Jomon series. These include a broad and low facial skeleton, straight upper orbital margins, prominent and broad nasal bones and long, flat and weakly curved clavicle shafts in Iwatsubo 1, long forearm bones, pilastric femora, long tibiae, and megaperonic fibulae in both Iwatsubo 1 and 2. Iwatsubo 1 and 2, however, differ from the average Jomon conditions in their higher estimated stature and larger circumferences of major long bones. Therefore, although Iwatsubo 1 and 2 are thought to have been direct decendants of Jomon populations, some unknown new environmental factors may have affected their statures and robusticity of long bones. The other Iwatsubo specimens are less informative because of their poor preservation or infant status.
Dog bones excavated from 11 Jomon and 2 Yayoi sites in Kagoshima Prefecture were investigated morphologically and osteometrically. The late and final Jomon sites (3, 500-2, 500 BP) were shell mounds at Izumi, Euchi, Ichiki, Muginoura, Kusano, Ushuku, Omonawa I, and Inutabu, cave sites at Katano and Kurokawa, and a site at Uwaigusuku. The early Yayoi sites (2, 300-2, 000 BP) were the Takahashi shell mound and a cave site at Atake. The total excavated pieces of bone numbered 373;102 from the Inutabu shell mound, 83 from the Kusano shell mound, 82 from the Euchi shell mound, and the rest from the other sites. Most pieces were from adult dogs, but some from Euchi, Ichiki, and Kusano shell mounds were from young dogs. The morphological characters of the bones, as large as those of today's Shiba dog, were nearly similar at each site. The estimated withers height from the intact bone lengths was 35-43cm, showing that the dogs belonged to HASEBE's small-sized dog group. It is suggested that in the late Jomon period, small dogs were already being kept by people throughout the entire area of Kagoshima, although a buried sample has not yet been found.
Characteristics of the fast speed walking in old men, primarily from the viewpoint of the ground reaction forces, were investigated in comparison with those during the ordinary speed walking. As a result, the following were recognized as the characteristics of fast speed walking in old men; (1) the walking speed, step length, and brake impulse as well as acceleration impulse began to decrease pronouncedly from the age group in their 60s, (2) the walking of subjects in their 60s and 70s were hastened from the ordinary speed level with almost the same ratios as in the younger subjects, (3) increase of the step length during the fast speed walking, against those during the ordinary speed walking, was smaller in subjects in their 70s than in the younger, (4) increase of the brake impulse during the fast speed walking, against those during the ordinary speed walking, began to decrease from the age-group in their 60s, while (5) that of the acceleration impulse remained unchanged with age. The principal component analysis revealed that (6) the contents of the fast speed walking are almost identical in ages between 20s and 50s, suggesting that they begin to change at one's 60s.
The dimensional differences between the right (R) and left (L) feet were investigated in each pair of 26 measurement items in Japanese adults (149 males and 178 females). The standard value of bilateral differences was determined, taking into consideration of the standard deviation of the bilateral difference (right minus left) in each item and variance calculated by the nested analysis of variance. The measurement error variance amounted to 25%-40% of total variance in males and 30%-50% in females. The frequency of subjects without bilateral difference was about 17% in males and about 74% in females for foot length, about 53% both in males and females for foot width, and about 45% both in males and females for ball-joint girth. Fifteen % of males had the most frequent pattern of L>R in foot length and L=R both in foot width and ball-joint girth, while 17% of females had the most frequent pattern of L=R in these three measurements. With respect to the foot girth measurements, 12% of males had the most frequent pattern of L=R in ball-joint and waist girths and L>R in instep girth, while 16% of females had the most frequent pattern of L=R in these three measurements.
Direct linear transformation (DLT) method was applied to the three dimensional anthropometry using slide film image, and the limitation of estimation accuracy was examined by comparing values obtained through the computation based on DLT procedures and manual measurement. The standard errors of estimated three dimensional coordinates were around 4mm in 1, 000mm×1, 000 mm×2, 000mm of calibration area. Also, the acceptable estimation errors of anthropometric dimensions were obtained through the present photogrammetry. The three dimensional slide film analysis with DLT method thus may be an useful photogrammetry for estimating anthropometric dimensions as well as spatial relations among anthropometric landmarks.