Thesis (doctoral)--Lund University, 1999. / Includes bibliographical references (p. 287-306). Also available on the Internet.

Research into the origins of our own social behavior begins with understanding how environmental elements lead to complex social interaction. Social structure emerges from these interactions as a bottom-up process, whose patterning constitutes the very framework of a society. Studies of behavioral mechanisms are important in determining the full repertoire that results in the social and dominance structures of a species. Hormones such as oxytocin and cortisol facilitate and fluctuate in response to social interactions and measuring their relative values among individuals is a valuable tool in testing functional hypotheses of behavioral mechanisms. The objective of this dissertation is to investigate several fundamental, under-, or previously unstudied behavioral mechanisms and hormonal correlates that shape the unique social system of bonobos. The first study describes the pattern of expression of harassment behavior among immatures and tests predictions generated by the Exploratory Aggression and Rank Improvement hypotheses. Results demonstrate that immatures use harassment to test the nature of existing inter-individual relationships and to explore the parameters of aggressive behaviors and furthers our understanding of juvenile development of aggression and integration into the dominance hierarchy. The second study describes the pattern of occurrence of infant handling and tests predictions generated by several functional hypotheses, including examining the relationship between oxytocin and handling behaviors. Results show a significant sex difference in expression of handling where, during adolescence, male interest in infants sharply declines whereas females continue to handle infants, the expression of which was correlated with oxytocin. These results primarily support the Learning-to-Mother hypothesis and provide insight into the role oxytocin may play in facilitating care-giving behaviors in young females. The final study explores the patterning of female sexual behavior and male aggression, and investigates whether male constraint of female choice imposes a cost to females through induction of a stress response. Results show that while females exercise unconstrained mate choice through proceptive behaviors, males influence female receptivity through aggression and sexual coercion, shedding light on the degree to which rank related asymmetry in male mating success reflects female choice vs. constraint of choice. This dissertation includes previously published and unpublished co-authored material.

The database on hand preferences in non-human primates provides inconsistent and inconclusive findings, and is plagued by gaps and methodological issues. I studied hand preferences in the bonobo, which is a very interesting model for investigating evolutionary hypotheses on human handedness. There are few previous data on bonobos and they are from small samples and for relatively simple tasks. I studied a large sample of 94 bonobos in three zoos and one sanctuary, on a variety of actions. Five studies were performed to record: 1. hand use for spontaneous daily actions (non-social). 2. hand use for the tube task , a task that requires a manipulative bimanual coordinated precise action. 3. hand use for using a stick as a probe ( termite fishing ). 4. hand use for spontaneous social actions and gestures, recorded during their social interactions (intra-specific) and during interactions with humans (inter-specific). 5. hand use for induced begging gestures (begging for food from the observer). The results show significant manual laterality in almost all the behaviours studied. The hand preferences were present on an individual basis. The numbers of right-handed and left-handed individuals were similar, indicating no group-level bias, for any of the actions studied. There was no significant effect of the settings, rearing history, sex and age (except in study 2 where adults were more right-handed than younger subjects). I examined different factors that have been proposed as selective pressures for the emergence of handedness. Laterality was influenced by: postural demands (posture, activity of the other hand), precision, grip type, manipulation or bimanual coordination, tool-use, throwing, communication. Notably, the laterality was very marked for the tube task , the termite fishing task and the begging experiment, which suggests that the factors involved in these tasks could be important factors regarding laterality.

No description available.

Les canaux semi-circulaires présentent un grand intérêt dans l'évolution. Des travaux récents ont montré que pour certains caractères, le génome humain est plus étroitement lié à celui du bonobo ou du chimpanzé que ces derniers entre eux. Dans ce contexte, il est important de comprendre le degré auquel les différences morphologiques et structurales entre ces trois espèces, reflètent les connaissances phylogéniques actuelles. Cette étude vise à comparer la variabilité anatomique des canaux semi-circulaires à partir de 260 examens tomodensitométriques d'homo sapiens, pan paniscus et pan troglodytes existants. Nous appliquons un modèle mathématique valide avec des examens micro tomodensitométriques et une quantification de l'erreur de mesure. Principalement, nous trouvons que les humains et les bonobos partagent plus de similarités entre eux qu'avec les chimpanzés par rapport a l'orientation tridimensionnelle de leurs canaux semi-circulaires, un résultat qui ne cadre pas avec les connaissances phylogénétiques actuelles. Une première hypothèse consiste en une évolution convergente dans laquelle les bonobos et les humains produisent indépendamment, des phénotypes semblables, peut-être en réponse aux pressions de sélection similaires éventuellement associées à des adaptations posturales. Une deuxième explication possible et plus parcimonieuse, c'est que la morphologie labyrinthique partagée entre le bonobo et l'homme représente la condition ancestrale à partir de laquelle les chimpanzés se sont déviés par la suite. La symétrie remarquable des CSC est le deuxième résultat majeur de cette étude pour ses implications dans la taphonomie. Il a le potentiel pour enquêter sur les fossiles altérés, déduire la probabilité de déformation post-mortem qui peut conduire à des difficultés dans la compréhension de la variation taxonomique, des relations phylogénétiques et de la morphologie fonctionnelle. / For some traits, the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other. Therefore, it becomes crucial to understand whether morphological differences between humans, chimpanzees and bonobos reflect the well known phylogeny. Here we investigate intra and extra labyrinthine semicircular canals morphology using 260 computed tomography scans of homo sapiens, pan paniscus and pan troglodytes. We apply a mathematical model validated with micro-computed tomography scans and measurement error quantification. We find striking differences between, on the one hand, humans and bonobos and, on the other hand, chimpanzees concerning the 3D orientation of their semicircular canals. This finding does not fit with the phylogenetic knowledge. The first hypothesis is convergent evolution in which bonobos and humans produce independently similar phenotypes possibly in response to similar selection pressure maybe associated with postural adaptations. A second possible and more parsimonious explanation is that the bonobo-human labyrinthine shared morphology represents the ancestral condition with chimpanzees being subsequently derived. The remarkable symmetry of the SCC is the second major result of this study for its implications in taphonomy. It has the potential to investigate altered fossil, inferring the probability of post-mortem deformation which can lead to difficulties in understanding taxonomic variation, phylogenetic relationships, and functional morphology.

付記する学位プログラム名: 霊長類学・ワイルドライフサイエンス・リーディング大学院 / 京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22634号 / 理博第4623号 / 新制||理||1664(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 古市 剛史, 教授 湯本 貴和, 教授 濱田 穣 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

xvii, 149 p. : ill. (some col.), maps / The ranging behavior of an animal can reveal much about the social and ecological conditions it faces. Food availability, feeding competition, population pressures, metabolic requirements and human influences can all influence the ranging behavior of individuals. For modern humans, the manner in which we move about our world is limited only by access to technology and other cultural factors. Of course, it has not always been that way. Based on recent fossil discoveries, our earliest bipedal ancestors more closely resembled the living great apes in morphology. Consequently, studies of great ape behavior have been used to reconstruct scenarios of early hominin behavior. And while much has been written about chimpanzee ( Pan troglodytes ) ranging in this regard, less is known about bonobos (Pan paniscus ). Along with chimpanzees, bonobos are our closest phylogenetic relative, existing today as a descendant of a common ancestor the Homo and Pan genera shared sometime around six million years ago. Despite their close taxonomic relationship, however, there are a variety of behavioral differences between bonobos and chimpanzees. The aim of this dissertation is to better understand these differences within the context of ranging and social behavior and apply the results to models of early hominin behavior. More specifically, I used a Geographic Information Systems (GIS) approach to examine general bonobo ranging data, the differences in ranging behavior between males and females, and the manner in which neighboring groups interact. Compared with chimpanzees, bonobos at Lomako range over a much smaller total area, are not territorial, and differ in the composition of social parties. In general, female bonobos are more gregarious and cohesive, moving in semi-stable groups I call "cliques", while males are less aggressive and more likely to move independently. These results likely reflect the high levels of food availability for bonobos at Lomako, reducing the level of feeding competition, and emphasizing social and mating strategies in group formation. Consequently, the spectrum of potential early hominin ranging behavior must be expanded from the current chimp-centric perspective. / Committee in charge: Frances White, Chairperson; Stephen Frost, Member; Larry Sugiyama, Member; James Schombert, Outside Member