Coexistence and co-evolution of the great apes and humans in the African tropical forest

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RESEARCH RESULTSOur project aims to clarify the coexistence and social evolution of the great apes (gorillas and chimpanzees) and humans (hunter-gatherers), through comparative analysis of environmental factors influencing their sympatry in the tropical forests where the ancestral hominin evolved. We have monitored seasonal and annual changes in climate and food availability and conducted surveys on the apes and humans in the two study sites (Moukalaba-Doudou National Park, Gabon and Kahuzi-Biega National Park, DRC), both of which are regarded as refuge forests during the past glacial periods. Data on utilization of forests and ranging patterns of habituated or semi-habituated groups of gorillas and chimpanzees were collected and analyzed in relation to their diet and food conditions. Our results suggest that gorillas, chimpanzees and humans have developed different foraging strategies while keeping the similar food preference. Gorillas are distributed in different habitats at the simi … More lar density. Their diet is varied drastically with food availability, but range size is constant across habitats. By contrast, chimpanzees tend to change association patterns and range size according to fruit availability. Hunter-gatherers use the central foraging strategies based on food sharing system. Our recent findings suggest that the foraging strategy of gorillas inhabiting the lowland tropical forest is intermediate between chimpanzees and gorillas inhabiting the montane forest. They tend to reuse the particular areas for feeding and nesting possibly due to high diversity and abundance of fruits as frugivorous chimpanzees, while they periodically shift their range as folivorous gorillas. These observations strongly suggest that inter-and intra-specific conflicts on resources constitute major factors promoting hominin social evolution under the sympatric conditions. Based on this view point, we will start a new project entitled "Evolutionary anthropology on conflicts and resolution of the great apes and humans" as a Grand-in-Aid for Scientific Research (S) from 2007. Less