I attempted to find basic bone morphology and bilateral asymmetry for the human paired radii based on intra-regional and side ratios for a total of 11 length, width, depth and girth measurements.Four hundred and seventy paired radii of Iraqis, Germans and Japanese were used for this purpose. The maximum bone length and 6 intra-regional ratios of the radius for Iraqis and Japanese exhibited significant sexual dimorphism in bone morphology, while the maximum bone length and 6 intra-regional ratios for Iraqis and Japanese of both sexes, as well as German males, also showed significant ethnic differences.On the other hand, the maximum bone length and 10 intra-regional ratios from the paired radii did not exhibit any significant side differences in bilateral asymmetries, al-though all of them showed significant side correlations.In addition, four side ratios for the bone length, and the robustness of the midshaft and distal end, exhibited significant sexual dimorphism and ethnic differences.On the basis of these results, the interrelations of basic, adaptive and bilateral bone morphology for the human paired radii were viewed in terms of bone growth and remodelling, biomechanics, cooperative use of the paired upper limbs, and differences in intrinsic and extrinsic factors for the Iraqis, Germans and Japanese.
Abstract Japanese macaques very often have a divided hypoglossal canal (DHC).Though not statistically significant, the incidence of DHC is lower in dental age class 2 than in other age classes, in males compared to females, and on right sides compared to left sides.The association between the right and left sides is extremely significant (chi-square=19.443), but the phi correlation coefficient (0.312) is not high, suggesting a low heritability estimate.It is suggested that a low heritability estimate within an individual population is not, in itself, an indicator of poor perfor-mance of the trait in population comparisons.
In order to describe molar enamel thickness more accurately, a new measurement method using a laser triangulation system has been developed and its repeating accuracy was tested.The method was then applied to investigate the chang-ing pattern of lateral enamel thickness along the distal protoconid crest.The results indicated that lateral enamel thickness at different sections tends to be comparable in relation to distance from the dentine tip.We expect this method to become an effective tool to investigate not only thickness of enamel but also its three-dimen-sional morphology.
In the present study, I examined the bilateral asymmetries of several morphological characters of the humerus of 63 modern Japanese (male 46, female 17) and 40 Jomon people (male 20, female 20) with the aim of distinguishing be-tween metric features that are strongly affected by mechanical loading and those that are not, and to discuss the loading conditions of the upper arms of Jomon people.The results were that the bilateral asymmetries of humeral length and all other mea-surements except for proximal epiphyseal breadth did not correlate significantly with asymmetries of diaphyseal geometric properties.Since the longitudinal growth of a long bone stops when its epiphyses are fused with the metaphyses while corticla remodelling goes on for life, the present results can be interpreted as follows: 1) Bilateral asymmetries in the longitudinal direction is likely to reflect the cumulative loading conditions to around an age of 20 years, and 2) bilateral asymmetries in the tranverse direction reflects loading conditions relatively close to the time of death.Regarding the loading conditions inferred for the upper arms of Jomon people, it is suggested that they were stronger than in modern Japanese and some hunter-gather-ers (Amerindians).The loading conditions of the upper arms of Jomon people were also likely to be less asymmetric than in other populations, while differing consid-erably between sexes.