Juichi Yamagiwa

Field studies on the African great apes have greatly reduced the anecdotal gap between apes and humans based on the findings of cultural behavior, self-medication, elaborated hunting, prudent alliance or intervention in agonistic interactions and extended sexual behavior in various social contexts. We have learned that most differences in the behavioral features of apes and us are not qualitative but quantitative.

When I was a student of Kyoto University in the 1970's, the Japanese primatologists discovered many behavioral features that are common to the great apes and humans. In the Laboratory of Physical Anthropology, I frequently experienced animated discussions on evolutionary trends from apes to humans, such as formation of human family, incest taboo or egalitarian sociality. I was strongly motivated to study human sociality by observing the great apes in the wild. The Japanese primatologists used anthropological methods to describe animal behavior by habituating them and identifying each individual. The late professor Kinji Imanishi advocated a new field of animal sociology and proposed guidelines of field research on wild animals. He believed that, in order to clarify the relationships between animal behavior and their social systems, data on how they recognize each other and on how their social relationships change with time should be collected by long-term field observations. I started my field works on Japanese macaques on Yakushima Island and then on wild gorillas in tropical forests in Africa. By spending a long time with gorillas in the dense forests, I have found many interesting hints for considering human evolution.

My findings on the aging cycle of gorilla social structure suggest that the creation of the sociological father may have played an important role in establishment of the human family. Affiliative relationships between a father and a daughter may promote avoidance of sexual interactions between them and may stimulate female dispersal from their natal groups. Other findings on social staring between gorillas suggest that their social interactions are not based on dominance hierarchies but rather on egalitarian sociality with frequent intervention in conflicts by a third party. The early hominids may have developed such social features as exogamy, an incest taboo or cooperation between different families by division of labor.

Recently, infanticides by extra-group males are argued as the major reproductive tactic aimed at stimulating females to resume reproductive cycling from the socioecological point of view. Frequent infanticides have been reported in a population of mountain gorillas, while no infanticide was observed in my study populationof eastern lowland gorillas. I compared social structure and individual migrations between the two populations and found marked differences in the group composition and the patterns of female transfer. Infanticides may promote female transfer into multi-male groups for seeking the stronger protection and association among kin-related males within a group. In contrast, the lack of infanticide may promote formation of one-male group and association among females at transfer. Such social flexibilities may characterize the population structure of gorillas. Similar consequences from violence by males probably influenced human sociality inthe past.

My recent research is focused on sympatry of gorillas and chimpanzees. During the major part of human evolutionary history, our ancestors coexisted with other hominid genera or species. However, weare living as a single species at present on the earth. How did our ancestors coexist with other hominids? Why and how didother hominids extinct? Sympatry of gorillas and chimpanzees may provide good suggestions to answer these questions.

Earlier studies in the 1960's and 1970's suggested that distinct niche differentiation reduced competition between them. However, my research shows that there is actually extensive overlap in diet and ranging between them. It seems likely that they have developed different foraging strategies and sociality to mitigate feeding competition, while keeping similar preference to succulent ripe fruits. Our ancestors may also have developed unique foraging strategy and sociality under sympatric conditions with other hominids.

Food sharing, co-feeding and division of labor may have been incorporated into the formation of human family. Continuing research on sympatric gorillas and chimpanzees will facilitate understanding the evolutionary history and ecological background on human sociality and mind in the near future.

Gorillas form a cohesive group like a human family	Mountain gorillas usually form a multi-male group where a putative father and a matured son coexist.
Pole Pole Foundation invites school children to observe wild gorillas in their natural habitats.	A mother and her infant moved between groups without infanticide in Kahuzi-Biega National Park.

The great apes have been driven to the point of extinction in most of their habitats, due to increased deforestation, bush-meat trade and epidemic diseases. In view of the urgent need to protect the great apes, I have engaged in various conservation activities. I have worked as a member of SAGA (Support for African/Asian Great Apes), a union of people who wish to promote conservation of the great apes in the wild and their welfare in captivity. We have organized a symposium once per year to discuss conservation measures and enrichment of captive environments. The seventh SAGA symposium was held at Kyoto University Clock Tower Centennial Hall and Kyoto City Zoo on November 12-13, 2004. More than 200 people attended the symposium and discussed environmental education and zoo education from various fields. I have also worked as a member of Pole Pole Foundation(POPOF), an NGO organized by people inhabiting the villages adjacent to the Kahuzi-Biega National Park, Democratic Republic of Congo, where gorillas and chimpanzees live sympatrically. A tree nursery, a handicraft center and a school for women and children were established for community-based conservation education. Such activities have played an important role in the spread of conservation knowledge and in the reduction of poaching. I hope our growing understanding of the great ape biology contributes to major improvement of their conservation status and to reconsideration of human beings as their closest neighbors on the planet.

Prof. Yamagiwa who presented a lecture for the general public as part of the SAGA symposium.	Exhibition booths of NPO organizations at SAGA7 Symposium. The theme of the exhibition was protection of apes.