The following five apomorphies are found in Callitrichidae.
1. The anterior lower teeth show short-tusked condition.
2. On first upper molar, the disto-lingual cusp (hypocone) is reduced.
3. On first upper molar, the lingual cingulm is reduced.
4. Third molars are absent.
5. Septa connect the promontory of tympanic cavity with the inner surface of auditory bulla.
The phylogeny of Callitrichidae is reconstructed as follows based on the synapomorphies. At first, Callimico were differentiated, followed by Saguinus, then Leontopithecus, and finally Callithrix and Cebuella were differentiated each other.

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Infant Japanese macaques are psychologically as well as nutritionally dependent upon their mothers. Near the age of one year, however, infants become independent of their mothers and increasingly involved in social interactions with other group members. Previous studies have shown that maternal separation during an infant's first year of life can produce social deficits and stereotyped behaviors. The present experiment was performed to determine the effects on infant behavior of prolonged maternal separation at 13 months of age. The subjects were three mother-infant pairs of Japanese macaques. Each of the three mothers was born and lived in the same free-ranging group for a period of time varying between 1 year and 5 years. One of the infants was born and lived in the free-ranging group for nine months. The two remaining infants were lab born. Data were collected during four weeks prior to separation, six months during separation, and four weeks following reunion in the laboratory. Individual differences were observed in certain aspects of infant behavior during each of the experimental stages. The present findings indicate that the behavioral differences between infants were correlated with the length of time the infants and their mothers had lived in the free-ranging group, the interactions between the infant and its mother during the pre-separation stage, and the interactions between the infant and its mother during the reunion stage.

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A total of 406 observations on dental eruption was obtained from 343 Japanese monkeys (Macaca fuscata) of known birthdays (Table 1).
The order of the beginning of eruption was estimated as (M₁, M¹), (I¹, I₁), (I₂, I²), (M₂, M²), (PPPP), (C, , C'), (M₃, M³) for male and (M₁, M¹), (I¹, I₁), (I₂, I²), (M₂, M²), (C, , P₃, P³, C', P₄, P⁴), (M₃, M³) for female.
Among 406 observations, 270 were used for statistics of the eruption age, because the remaining 136 which were obtained from monkeys of Shiga and Koshima show a fair degree of delay in the eruption age as a whole. The statistical results were shown in Tables 2 and 3, and a norm of the eruption age as a tentative interpretation was given in Table 4 with a footnote concerning the delay of eruption in monkeys of Shiga and Koshima. Interpretation of the delay in these monkeys is difficult, though the delay in monkeys of Koshima may be related to the general delay of their growth which has been caused by their isolation on a small islet.
From the comparison of the present results and related reports on macaques (Table 5), it is apparent that among four species, M. fascicularis, M. mulatta, M. nemestrina and M. fuscata, the eruption is comparatively late in M. fuscata for most teeth, and it is generally earlier in female than male for every tooth except for M3 which erupts at similar age in both sexes or earlier in male than female especially in M. mulatta. Sexual difference in the eruption age of C, and possibly of P3, is relatively small in M. fascicularis and large in M. nemestrina. It seems that these interspecific differences are more or less related to those in body size and canine size.

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Theoretical framework of sociobiology can be regarded as Lakatosian “advanced research program, ” which has high probability of problem solution and a flexible metaphysical structure. Some theories, however, should be expanded to apply to primate behavior, because a lot of primate behavior does not seem to have direct genetical bases. Learning ability of primates is higher than that of non-primates and some of higher primates even show cultural behavior. So that, it is necessary to clear up the relation between phenotype and behavior to establish primate sociobiology. For this purpose, a new concept on their relation, the “phenotype/sub-phenotype network” model, is presented here. If a behavioral parameter is genetically determined phenotype, behavior(s) which are influenced with this parameter can be called “sub-phenotype(s).” I also discuss some theories on cultural transmission and evolution, and confirm that the framework of sociobiology is useful to reveal this problem. These theories and models will provide fruitful perspectives on human origin and evolution, applied to primate pre-cultural behavior. Finally I discuss some problems and perspectives on primate sociobiology. On the development of primate sociobiology, it seems to be emergent and important to apply multiple variate genetic theory that has been developed by R. Lande.

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To make the primate evolution clear is the one of main purpose in primatology. Speciation is an important aspect of evolution. When a species is defined as a group of interbreeding natural pupulations that are reproductively isolated from other such groups, a study of speciation must involve an examination of reproductive isolating mechanisms. What kind of the mechanisms do work in a primate speciation? Is there any unique mechanism in primates, exhibiting great encephalization and excellent learning abilities? These questions are discussed in case of genus Macaca. Behavioral isolating mechanism seems to be the most probable mechanism for the genus. In the application of the mechanism to the genus, however, it seems to be necessary to expand the meaning of behavioral isolation. Because, macaque monkeys can learn a species concept and discriminate a species from the others with the concept. And also they can recognize their conspecifics. The ability to make such discrimination may be an important factor in behavioral isolation in genus Macaca. This expanded behavioral isolating mechanism through a species discrimination learning is named as the “psychological isolating mechanisms”. This mechanism may have an important meaning in the human evolution.

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Sociobiology and Japanese primate sociology are discussed to develop theories on evolution of social structures and behaviors in primates. Central problems on applying sociobiology to the primate evolution may be concepts of phenotype and selection pressure. Phenotypes for primate social structures and behaviors would be correlated each others (multi-polar), and be hierarchically organized (multi-level). For the selection pressure, “active selection pressures”, such as species recognition and sociality, may be critical for the primate evolution. Since the “active selection pressure” has properties of phenotype, we insist “dualism” of the active selection pressure and phenotype could be a critical mechanism of the primate evolution. On the other hand, primate sociology, which has been leaded by Imanishi, is characterized by its idea of “holism”that individuals serve the prosperity of species. Although Imanishi's primate sociology has been pointed out to differ from sociobiology in several points, we consider that it can be fruitfully reconstructed in the framework of neo-Darwinism when the idea of “holism” is abundant. Further, Itani has shown basic social units as the phylogenetic constraint. Since the phenotypic dynamic theory of neo-Darwinism involves phylogenetic constraint, it could reveal evolution of primate social structures. Thus, Imanishi's primate sociology and Itani's theory could be reconstructed in the framework of neo-Darwinism. The reconstruction would be fruitful to develop theories on evolutionary mechanisms of social structures and behaviors in primates.

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