In this paper we begin by examining two currently used methods which solve matrices of pairwise distances in terms of additive trees, one proposed by Fitch and Margoliash (1967) and the other proposed by Saitou and Nei (1987). Neither method is exhaustive in the sense that not all possible trees are tested to ensure that the best solution has been reached. We develop a method here which decomposes any unrooted binary tree with a specified topology by a pair of matrices. Also, this method can generate trees using matrices. Thus it can be efficiently implemented on computers. Once the best solution is found by standard matrix techniques, the matrices can be recomposed into tree form.

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No information has been thus far provided concerning the archaeology of Rattanakiri Province, highland Cambodia. Through interviews with the local people who are engaged in open-air gem mining, however, nearly ten prehistoric sites were located and some artifacts collected from the sites were recorded in this region. Based on the distribution of the sites, it is apparent that there was intensive use of the inland riverine zone by the prehistoric population during the Neolithic and/or Bronze Age. More thorough and systematic interviews with locales should enable us to locate more prehistoric sites situated in similar and in different environmental settings.

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Immunoglobulin Cα gene encodes a constant region of heavy-chain of IgA antibody, and the hinge region is located between CH1 domain and CH2 domain. The hinge region functions to increase efficiency of antigen binding by varying distance between two antigen recognition sites. The constant region of IgA has been considered to be conservative, but we previously reported that immunoglobulin Cα genes of great apes showed evolutionary hypervariability mainly in the hinge region (Kawamura and others, 1990). To know whether this hypervariability is also the case among Old World monkeys, we carried out PCR-SSCP analysis for macaque, baboon, and leaf monkey. The result clearly showed evolutionary hypervariability in the hinge region among Old World monkeys. Adding to this inter-species variability, intra-species variabilities were also observed in multiple species such as rhesus macaque, crab-eating macaque, Assamese macaque, and hamadryas baboon. Furthermore, polymorphism was likely shared by multiple macaque species (trans-species polymorphism). These results suggest the indispensability of hypervariability in the hinge region for these animals. Some kind of positive selection, like the overdominance at the MHC loci (Klein and others, 1993) might be responsible for this hypervariability.

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The Northeast and East Asian populations were analyzed according to four batteries of craniometric characters. The results between the different batteries, however, were less than clear-cut. There are some exceptional cases, which differ from the widely known populational affinities based on many anthropological traits. For example, the Aleut showed a close affinity with not only the other Arctic peoples but also the Ainus. The Ekven, the Iron age ancestors of the Arctic peoples, were isolated from the recent Arctic populations due to their hyperdolichocrany. Selection of measurement variables must be one of the most serious problems in anthropology as the efficacy of discrimination of respective metric variables.

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