There is a considerable corpus of evidence indicating that athletes succeeding in certain sports have distinctive body shapes that differ according to the demands of the type of sports and competitive level. The aim of this study was to determine the specific morphological characteristics of young male athletes compared with non-athlete students in Indonesia. Anthropometric measurements of 19 badminton players, 96 soccer players, 74 volleyball players, and 51 non-athlete undergraduate students, aged 16 to 28, were obtained in 1994 and 1995. Stature, body weight, bicondylar breadths of the humerus and femur, calf and upper arm circumferences, and skinfolds (at triceps, subscapula, calf, and supraspine) were measured for each subject. Heath-Carter somatotypes were determined in all the subjects. The results of the ANOVA of the body measurements showed that the three groups of athletes and the non-athlete students were heterogeneous: the badminton players were shorter and lighter with greater skinfold values among the athlete groups; the soccer players were relatively shorter and with smaller skinfold values and greater arm and leg girths; and the volleyball players were taller and heavier with smaller elbow and knee breadths and very small skinfold values. The non-athlete students were characterized by greater arm girth, elbow breadths, knee breadths, and back and leg skinfolds. In mean somatotype category, the badminton players were ‘central’ (3.3-3.7-3.7), the soccer players were ‘balanced mesomorph’ (2.7-4.9-3.0), the volleyball players were ‘mesomorph-ectomorph’ (2.4-3.5-3.7), and the non-athlete students were ‘ectomorphic mesomorph’ (2.7-5.2-3.8). Comparisons of international scope with each of the different sports showed that the Indonesian players were extremely short and light.
An osteometric approach was used to demonstrate the relationship between vertebral body morphology and bipedal standing using 17 rats, which had been divided into control and exercise groups. Only the latter group (n = 9) performed a series of bipedal standing exercises using operant conditioning. Statistical analysis was conducted to allow for inter-group comparisons with respect to six linear dimensions and five indices for each of the 24 vertebral bodies, from the third cervical through the last lumbar vertebrae. Detected effects of bipedal standing exercises on the vertebral body were as follows: (1) dorsal height decreased from the caudal thoracic to the lumbar vertebrae; (2) the dorsoventral diameter of the cranial surface increased at the thoracolumbar level; (3) the dorsal-to-ventral height ratio decreased in the lumbar vertebrae; (4) the dorsoventral-to-transverse diameter ratio of the cranial surface increased in the middle thoracic and lumbar vertebrae; and (5) the height-to-dorsoventral diameter ratio decreased in the fifth thoracic vertebra, and from the tenth thoracic to the fourth lumbar vertebrae. In vertebral bodies at the thoracic and lumbar levels, experimentally induced osteological changes such as wedging, dorsoventral elongation, and craniocaudal robusticity were discussed in terms of their comparative morphology in humans and quadrupedal mammals, and then compared with those of a bipedally trained Japanese macaque.
Intergeneric morphological variation of the glenohumeral joint surface was investigated among three ateline genera (Ateles, Lagothrix, Alouatta) and compared with Cebus (an ancestral morphotype of atelines) and Hylobates (a specialized brachiator) to reveal characters associated with forelimb suspensory behavior. Seventy-six skeletal specimens were examined, and articular surface curvature was measured by a three-dimensional digitizer. It was found that Ateles exhibits joint features distinct from the other atelines, but resembles Hylobates in its large breadth–length ratio of the glenoid surface and the humeral head, a relatively spherical humeral head, and a dorsoventrally extensive humeral head relative to the glenoid surface. These morphologies are likely to be related to brachiation, rather than to climbing behavior. A dorsoventrally extensive glenohumeral joint is interpreted to facilitate an increased stride length during brachiation. Lagothrix was found to show many primitive features that are shared with Alouatta in spite of its forelimb suspensory behavior. This may be related to the less specialized mode of forelimb suspensory behavior in Lagothrix compared with Ateles. Those characters that apparently correspond to dependency on suspensory behavior can be useful in interpreting the positional behavior of extinct primate taxa.
Inter-populational heterogeneity of the Neolithic Jomon hunter-gatherers of Japan was examined via 21 non-metric dental traits. Skeletal samples from nine local sites and five regional groups of the middle to final stages of the Jomon period were analyzed, and inter-site comparisons were made among five representative sites (Ubayama, Nakazuma, Ikawazu, Yoshiko, and Tsukumo). Statistically significant differences were found in 4/21 traits in the inter-site comparisons, and in 5/21 traits in the inter-regional comparisons between the Hokkaido, Tohoku, Kanto, Tokai, and Sanyo groups. Smith’s distances suggest that the inter-regional differences within the Jomon assemblages are minor when compared with differences from the non-Jomon samples such as the Yayoi immigrants, Kofun, and modern Japanese. Furthermore, examination of the wider geographical variation of the Jomon people (eastern versus western) revealed significant differences in only 2/21 traits. Distance analysis showed that the eastern and western Jomon groups clustered together, and exhibited the greatest affinities with present-day Southeast Asians among comparable East Asian and Pacific population samples. The Jomon people can be collectively regarded as relatively homogeneous, within the broader context of East Asian and Pacific intra-population variation.
Twenty-four non-metric tooth crown traits of Miyako and Ishigaki Islanders, from the southernmost Ryukyu Islands, were investigated and compared with those of neighboring populations. The frequency of double-shoveling in Sakishima samples, and especially, Ishigaki Island, is lower than that found among Atayal people (Taiwan) and main-island Japanese. The frequencies of protostylid and cusp 6 in Miyako and Ishigaki Islanders are comparable to those in Hokkaido Ainu and lower than in main-island Japanese and Atayal. Miyako and Ishigaki Islanders, as well as other Ryukyuans, are basically more similar to main-island Japanese than to Ainu, while being situated between main-island Japanese and Ainu in terms of both mean measure of divergence (MMD) and R-matrix methods. However, Ishigaki and Miyako Islanders are relatively close to Hokkaido Ainu among Ryukyu people and main-island Japanese, as suggested in some previous preliminary studies. The estimated Fst (the ratio of among-group variation to total variation), using an average heritability rate = 0.55 for the non-metric tooth crown traits used in this study, displayed low levels of inter-regional variation, as already indicated in analyses of genetic, cranial and dental metric data. Meanwhile, the relatively large diversity of Ryukyu Islanders based on Fst suggested long-term isolation or poor intra-island contact among the Ryukyu Islands. The lower observed variation compared with the expected variation in most Ryukyu samples may reflect a greater degree of genetic drift in the Ryukyu Island chain.
Ante-mortem tooth loss (AMTL) in a medieval Japanese ‘Yuigahama-minami’ population excavated at Kamakura, Kanagawa prefecture, was examined. In the medieval period, Minamoto Yoritomo established the shogunate in Kamakura, and many battles were fought around Kamakura. Human skeletons from the medieval sites in Kamakura are considered to be casualties of these battles. The AMTL ratio in Kamakura medieval skeletons, as reported in previous work, is very low. If these medieval skeletons derive from death in battle, they can be expected to be comparatively younger than those deriving from natural death; and if the ratio of younger skeletons is high, the AMTL ratio would naturally be expected to be comparatively low. The findings of the present study indicate that AMTL ratios in this medieval population, not only in the young, but also in the elderly, were low for the period. A comparison of AMTL ratios in the Yuigahama-minami with the Miwanoyama medieval population in Chiba prefecture indicates that the low AMTL ratio in the former was not a common characteristic of the medieval Japanese, and that there were regional differences in AMTL ratios in the period. Comparisons also show that the ratios of dental caries in both the young and elderly Yuigahama-minami medieval population were lower than among other early Japanese. Not only the AMTL, but also the dental caries ratios of Yuigahama-minami males were significantly lower than those of Yuigahama-minami females, both young and elderly. It therefore appears that Yuigahama-minami males had exceptionally good dental health.
Investigations of nonhuman primate mandibles have demonstrated that they are bent, twisted, and sheared during the power stroke of mastication. Inferences have been made regarding potential relationships between local stress patterns and the external morphology of the mandibular symphysis. This study reports the quantitative assessment of cross-sectional bone distribution patterns in the modern human symphysis by use of high-resolution microfocal X-ray computed tomography. Parameters that were examined include (1) bone substance area, (2) the ratio of bone substance to total cross-sectional area, and (3) cortical thicknesses along the perimeters of the symphyseal cross-section. The observed bone distribution was then compared with the hypothetical patterns of mechanical stress during mastication. Results showed that cortical bone was significantly thicker on the lingual than on the labial aspect of the symphysis at all superoinferior levels. The thickest cortical bone was observed on the lingual aspect of the symphysis immediately inferior to the mental spine, and labially at the mental protuberance. Bone area measurements were largest and second largest in the inferolingual and inferolabial quadrants of the symphyseal cross-section. These results show that bone is concentrated particularly at the lower lingual aspect of the symphysis, which is thought to experience high concentrations of tensile stress during mastication. Such a bone distribution pattern contributes to decreasing stress gradients in the mandibular symphysis, and therefore provides some support to the idea that bone distribution of the mandibular symphysis is in part determined by function.
Wild troops of the Japanese macaque (Macaca fuscata) live in various habitats within the Japanese archipelago. The social relationships of males can be elucidated through intraspecific comparisons of social conditions between populations of different habitats. Previous research has shown that males associate with one another more frequently on Yakushima island than on Kinkazan island, whereas male–female and female–female relationships did not differ between populations that occupy the two different habitats. However, this study did not compare the social relationships of males between habitats during the mating season, when males are expected to compete for fertile females more aggressively within and between troops. The present study compared male behavior in Yakushima island and the Shimokita peninsula populations during the mating season and found that males exchanged affiliative behaviors with one another more frequently on Yakushima island. The socionomic sex ratio (SSR: adult males/adult females) was higher in the Yakushima island troop, and this troop was involved in inter-troop encounters more frequently. In Yakushima island, more non-troop males were observed around the troop and were frequently involved in agonistic interactions with troop males. Yakushima island troop males are likely to affiliate with one another to reduce tension among themselves, in order to cooperatively attack neighboring troops and non-troop males that appear to copulate with fertile females.
The free gait of 52 healthy elderly persons was examined. All the subjects were volunteers, aged 65 years or older, and lived in the community in the Kaga area, Ishikawa Prefecture, Japan. They were healthy and active enough to attend the study location by themselves. The comparison group of young adults consisted of 20 volunteer students. The percentages of females and males were similar in the two groups. The healthy elderly walked more slowly than the young adults. Their slower speed was largely caused by their shorter stride length. Differences were still observed between the young and elderly groups when gait parameters were presented in the form of dimensionless numbers. The elderly were weaker in grip strength and had shorter single-leg balance with eyes open than the young adults. The number of steps per day correlated negatively with age within the elderly group. Negative correlations between age and walking speed, as measured directly or in terms of dimensionless numbers, and between age and stride length were also observed within the elderly group. The relative stance phase duration correlated positively with age within the elderly group. Slow speed may be related to low daily activity, reduced muscle power, and diminished balance ability. Long stance phase duration and slow speed in the elderly could be an adaptive characteristic in response to impaired balance.
Lines 17 and 18 from Bottom
Wrong:The beginning suggests a potential trigger for the ensuing changes.
Right:However, the beginning of food production was an important transition which suggests a possible trigger for later changes.