Auditory exostoses were investigated macroscopically in a total of 1209 crania. This sample represents 24 ancient human populations covering the circum-Pacific area of Remote Oceania through Southeast and East Asia. Regional variations in its frequency were considered. It was found that there were several foci in the area, where the character frequently occurred in the past; specifically, New Zealand, Easter Island, the Marquesas, Tonga and Japan. This finding suggested that prehistoric Polynesian and Japanese populations were engaged in the heavy exploitation of marine resources through diving, taking into account the so-called 'thermal aquatic hypothesis' on the causative relationship between diving for marine resources and the exostosis development. It is difficult, however, to discuss the extent of aquatic activities for the populations in Southeast Asia, because possibly due to the hot climate there through the year, the development of exostoses is not as pronounced. Though largely speculative, the present results may also provide a kind of evidence of a biological relationship in the rehistoric time between Polynesians and some East Asians, represented in the present paper by the Jomon and Yayoi Japanese.
Sixteen Neanderthal mandibles together with those of five European middle Pleistocene Homo specimens, and over one hundred prehistoric Jomon crania from Japan were examined to clarify whether the presence of large retromolar space, one of the unique facial features of Neanderthals, is at least in part a consequence of forward migration of the teeth caused by heavy interproximal attrition. When the Neanderthal and the Jomon samples were divided according to age or magnitude of tooth attrition, the reduction of olar teeth length and the enlargement of retromolar space with the vance of age or tooth attrition were indicated in both samples. The results suggest that the retromolar space is a morphological complex containing heterogeneous factors, one of which is the secondarily acquired one caused by forward migration of the postcanine dentition.
It has been shown that the typing of urinary JC polyomavirus (JCV) DNA offers a novel means of tracing human migrations. We used this approach to elucidate the colonization of the Japanese Archipelago. Approximately 1, 000 JCV DNA-positive urine samples were collected throughout the Japanese Archipelago, and used to amplify a 610-base-pair JCV DNA region (IG region). We determined about 100 IG sequences, from which a phylogenetic tree was constructed to classify them into distinct genotypes. The rest of the amplified fragments were classified into genotypes on the basis of the results of a restriction fragment length polymorphism analysis. Two major (CY and MY) and three minor JCV genotypes (SC, B1-a, and EU) were identified. There was marked variation in the frequency of these JCV genotypes among the sites of sample collection. For example, MY was more frequently detected in northeastern areas and CY was predominant in southwestern areas. The possibility that the detection of EU in Japan is a result of recent Caucasian immigration was excluded by a phylogenetic comparison of Japanese and European EU isolates. These findings suggest that not only two major groups carrying CY or MY but also three minor groups carrying SC, B1-a or EU migrated to the Japanese Archipelago and that all contributed to founding modern Japan.
Computer simulations of human infant walking, changing from supported walking with weight support to independent bipedal walking, were conducted to identify the biomechanical factors of the neuro-muscular system necessary to acquire bipedal walking. We simulated the autonomous acquisition of independent walking by repeating walking trials and modifying neuronal structures and parameters so that walking efficiency is maximized, and forces supporting the upper body are minimized. The results of simulation showed that reinforced interaction with the system of body dynamics, such as feedback from somatic senses, especially information concerning angular velocities of joints, is essential to the development of walking. Other significant factors for bipedal walking are the development of neuronal feedback about the hip joint position, which determines the posture of the upper body, and improvements in the extensors' ability to produce joint moments.
Censusing was done by direct observation along three survey routes to estimate the distribution and abundance of medium- and large-sized diurnal mammals in the Kasoje area of the Mahale Mountains National Park, western Tanzania between 1995 and 1996. The census area is located within the home range of M Group chimpanzees who have been observed to consume at least 14 species of sympatric mammals. The vegetation along the three census routes was divided into two types of habitat (forest vs. woodland); as a result, six census subunits were distinguished. Preference of habitat by eight species of mammals-red-tailed monkey, blue monkey, yellow baboon, red colobus monkey, bushbuck, blue duiker, warthog, and forest squirrels-has been suggested and their group and/or individual densities have been estimated in at least one census subunit. In 1974, most villagers moved out of the Kasoje area following a government edict and the wild animal population in general appears to have increased in number since then. However, expansion or contraction in distribution of three species of mammals at Kasoje since the 1970s differs from species to species: yellow baboons and warthogs have apparently expanded their ranges while vervet monkeys seem to have contracted theirs. The abundance of red colobus monkeys appears to correspond with the high frequency of colobus hunting by the chimpanzees. However, it should be explained in the future why the second most abundant red-tailed monkeys, another resident arboreal species, have been eaten only infrequently by them. Further accumulation of observations on actual encounters between the chimpanzees and their potential prey is necessary.
We studied the effects of body segment inertia parameters (BSPs) on the results of biomechanical analyses of human movement. The vertical jump was taken as an example. A subject was asked to perform 15 vertical jumps. He was measured using an automatic coordinate acquisition system and a force platform. Kinematic and kinetic variables were computed using five BSP sets: 1) Average for three-year-old Japanese children reported by Yokoi and others (1986), 2) Regression equation for young adult Japanese athletes reported by Ae and others (1992), 3) Average for young adult Japanese athletes reported by Ae and others (1992), 4) Average for young Japanese adults reported by Matsui (1956), and 5) Average for aged Caucasian cadavers reported by Chandler and others (1975). Vertical displacement and velocity for body segments and for the whole body exhibit few differences among the five sets. In time-series curves for each joint torque, the variance shown by a single subject was more pronounced than the variance due to differences in BSPs. These results suggest that selection of BSPs apparently has little effect on the results of kinetic analyses of human movement and on conclusions based on these results.
To scrutinize the geographical clines of allele frequencies of the group-specific component/vitamin-D binding protein (GC) system in Japan, the GC types in nine populations of southwestern Japan including Okinawa were determined. The frequencies of the common alleles in the island populations, especially, Yakushima and Miyako were found to be scattered more extensively than those in the populations of the mainland Japan. GC*1A2 was polymorphic in all populations except in the southwesternmost islands, Miyako and Ishigaki. The geographical clines of GC*1F, GC*1S and GC*2 frequencies are discussed in connection with the migration of the Yayoi era.